Reticularized Silver Nanoclusters: From Luminescence to Sensing

Abstract

Silver nanoclusters (Ag NCs) occupy a rare chemical space where atomic precision, quantum-confined electronic structures, and rich excited-state behavior converge, yet their practical utility is often limited by structural fragility, environmental sensitivity, and weak processability. Reticularization offers a powerful solution by transforming discrete Ag NCs into crystalline extended architectures in which cluster cores, protective ligands, bridging linkers, and pore environments operate as an integrated functional lattice. This Review examines reticularized Ag NCs, or Ag nanocluster metal–organic frameworks (Ag NCMOFs), as an emerging class of programmable optical and sensing materials. We discuss how Ag cluster nuclearity, ligand-shell chemistry, linker electronics, framework dimensionality, topology, and confinement collectively dictate stability, intercluster communication, charge-transfer pathways, and luminescence. Particular attention is devoted to the photophysical consequences of reticular assembly, including framework-rigidified emission, cluster–linker excited states, triplet-state activation, ratiometric fluorescence–phosphorescence, guest-modulated color changes, circularly polarized luminescence, and optical memory. We then highlight sensing platforms in which crystalline Ag-cluster frameworks translate oxygen diffusion, volatile-organic-compound uptake, explosive recognition, metal-ion binding, antibiotic interaction, amino-acid recognition, and water-induced lattice transformation into optical or Raman-readable outputs. Beyond sensing, we survey emerging roles in catalysis, electrocatalysis, photonics, electronics, antimicrobial interfaces, and molecular diagnostics. By connecting atomic structure to framework-level function, this Review presents Ag NCMOFs not as simple assemblies of emissive clusters, but as reticularized quantum materials in which periodic order converts fragile molecular emitters into robust, adaptive, and information-rich functional solids.

1. Introduction

The pursuit of structural precision has long served as a central theme in nanoscience. Among the diverse classes of nanoscale materials, atomically precise metal nanoclusters (NCs) occupy a particularly intriguing regime in which matter exists neither as isolated atoms nor as bulk metals, but within an intermediate domain where every constituent atom contributes measurably to the overall properties of the material. − Typically comprising several to a few hundred metal atoms and possessing dimensions below approximately 3 nm, NCs represent molecularly defined metallic species whose atomic compositions, geometric structures, and electronic configurations can be determined with near-crystallographic precision. − Unlike conventional nanoparticles, whose properties are often statistically averaged over distributions of size and shape, NCs exhibit discrete electronic structures arising from quantum confinement effects, resulting in molecule-like optical, electronic, magnetic, and catalytic behaviors. Their architectures generally consist of a metallic core surrounded by an organic ligand shell, with each component exerting a profound influence on the resulting physicochemical characteristics. The metal core functions as the primary repository of electronic states and determines the fundamental identity of the cluster through its nuclearity, geometric arrangement, metal–metal bonding pattern, and electronic shell structure. − Subtle variations in atomic count can dramatically alter thermodynamic stability, redox behavior, photophysical response, charge-carrier dynamics, and catalytic activity, giving rise to the well-known atom-by-atom sensitivity that distinguishes NC chemistry from conventional nanomaterials. The ligand shell, meanwhile, plays a far more sophisticated role than simple stabilization. Beyond protecting the metallic core from aggregation and decomposition, ligands regulate charge distribution, govern cluster growth pathways, mediate host–guest interactions, control intercluster communication, and influence excited-state relaxation processes. , Together, the core and shell establish a highly cooperative molecular architecture in which structure and function become inseparably intertwined. Over the past two decades, advances in synthetic methodologies, crystallographic characterization, mass spectrometry, and theoretical modeling have transformed NCs into one of the most active frontiers of nanochemistry. Atomically precise NCs have been explored extensively in catalysis, − photocatalysis, − electrocatalysis, − energy conversion, − bioimaging, − sensing, − nonlinear optics, − molecular electronics, − chiral recognition, − and quantum materials research. − Nevertheless, despite remarkable progress, NCs continue to face persistent challenges associated with low synthetic yields, demanding purification procedures, structural heterogeneity, limited processability, and difficulties in preserving structural integrity under operational conditions. Consequently, significant efforts have been devoted not only to improving cluster synthesis and separation but also to developing strategies capable of extending NC functionality beyond the limitations of isolated molecular species. Within this context, silver nanoclusters (Ag NCs) have emerged as one of the most fascinating subclasses of atomically precise nanomaterials. − Benefiting from the relatively high abundance and lower cost of silver compared with other noble metals, Ag NCs have attracted enormous attention owing to their rich photophysical characteristics. Quantum confinement within ultrasmall silver cores generates discrete electronic states that give rise to intense photoluminescence, tunable emission wavelengths, long-lived excited states, and complex energy-transfer pathways that are often inaccessible in larger nanoparticles. Ligand-protected Ag NCs display remarkable diversity in optical absorption profiles, emission colors, and excited-state dynamics, enabling their exploration in luminescent materials, photonic devices, and sensing platforms. At the same time, however, the intrinsic chemical lability of silver remains a formidable obstacle. The high susceptibility of Ag­(I)/Ag(0) species toward oxidation, photoinduced degradation, structural reconstruction, and environmental perturbation frequently compromises long-term stability and limits practical deployment. Thus, while atomically precise Ag NCs possess exceptional photophysical potential, realizing this potential in robust and functional materials remains a central challenge for the field.

One of the most compelling solutions to this challenge has emerged through reticularizationthe deliberate transformation of discrete nanoclusters into periodic, crystalline architectures. Isolated NCs, despite their structural elegance, inherently suffer from instability, aggregation, luminescence quenching, limited processability, and a lack of long-range structural organization. Reticular chemistry provides a fundamentally different paradigm by enabling molecular building blocks to be assembled into ordered frameworks with predetermined connectivity and topology. − Historically, the development of metal–organic frameworks (MOFs) has relied predominantly on single metal ions or small polynuclear secondary building units (SBUs) as lattice nodes. , However, a transformative conceptual shift has recently emerged in which atomically precise NCs themselves become the lattice points of extended crystalline materials. These nanocluster metal–organic frameworks (NCMOFs) establish a unique bridge between molecular nanochemistry and framework science by embedding structurally defined metal clusters within periodic porous architectures. − Unlike conventional MOFs, which are typically constructed from single metal ions or small polynuclear SBUs, NCMOFs employ atomically precise, ligand-protected metal nanoclusters with defined nuclearity and intrinsic electronic structures as framework nodes. Consequently, the nanocluster functions not merely as a structural junction but as an electronically and photophysically active building unit whose molecular characteristics can couple with framework connectivity to generate properties distinct from those of conventional MOFs. NC nodes possess precisely encoded nuclearity, geometrical complexity, delocalized electronic structures, and multiple chemically addressable metal sites. Their incorporation into reticular architectures therefore introduces functionalities that cannot be achieved through simple ionic nodes alone. This lattice-point design philosophy enables electronic communication, redox flexibility, cooperative catalysis, and spatial anisotropy to be encoded directly at the atomic level while simultaneously benefiting from the site isolation, robustness, and architectural programmability of crystalline frameworks. As a consequence, material properties become emergent features of both the cluster and the network in which it resides. Among NCMOFs, silver nanocluster MOFs (Ag NCMOFs) constitute an especially intriguing family because they address the fundamental weaknesses of Ag NCs while preservingand often enhancingtheir desirable photophysical properties. − A landmark example was provided through the reticular assembly of Ag₁₂ NCs with bipyridine linkers, demonstrating that framework integration can dramatically improve resistance toward oxidation, air exposure, and photodegradation while simultaneously enhancing luminescence efficiency. Since then, a remarkable structural landscape has emerged. Ag NCMOFs have been constructed from nanoclusters spanning a broad range of nuclearities, including Ag₅, Ag₇, Ag₈, Ag₉, Ag₁₀, Ag₁₁, Ag₁₂, Ag₁₃, Ag₁₄, Ag₁₅, Ag₁₆, Ag₁₈, Ag₂₀, Ag₂₇, Ag₅₄, and larger cluster motifs. Equally diverse linker systems, encompassing bidentate, tridentate, tetradentate, and multifunctional bridging ligands, have enabled the generation of one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) architectures exhibiting widely varying topologies and pore environments. Importantly, reticularization is not limited to linker-mediated assembly. In several linker-free or organic-spacer-free Ag nanocluster frameworks, neighboring clusters are directly organized through shared surface ligands, metallophilic Ag···Ag interactions, or small inorganic/anion bridges such as SbF₆ ^–, NO₃ ^–, and carboxylates, producing extended frameworks without conventional multitopic organic linkers. − Such direct cluster-to-cluster coupling creates structurally continuous pathways that facilitate energy migration, charge transport, and collective photophysical behavior while simultaneously stabilizing the cluster cores. Consequently, Ag NCMOFs should not be viewed merely as frameworks containing nanoclusters, but rather as condensed-phase manifestations of nanocluster chemistry in which atomic precision, periodic order, and collective functionality become inseparably integrated.

The rapid expansion of Ag NCMOF research has generated a rich and multidimensional field spanning synthetic chemistry, structural science, photophysics, sensing, catalysis, and materials engineering. Yet despite the growing number of reports, the underlying principles governing how reticular organization transforms the properties of Ag NCs remain fragmented across the literature. This Review aims to provide a comprehensive perspective on the evolution of reticularized Ag NCs and to establish conceptual links between atomic structure, framework architecture, and emergent functionality. We first discuss the structural foundations of Ag NCMOFs, including synthetic methodologies, cluster nuclearity, linker design, dimensionality control, and framework topology. Particular attention is devoted to understanding how reticular assembly modifies the intrinsic characteristics of Ag NCs through confinement effects, rigidification, intercluster coupling, and cooperative interactions between cluster nodes and organic components. We subsequently examine the photophysical landscape of these materials, highlighting the origins of luminescence, mechanisms of emission modulation, and the emergence of optical behaviors that are absent in either isolated nanoclusters or free ligands. Special emphasis is placed on luminescence-based sensing applications, where the combination of structural robustness, accessible porosity, and environmentally responsive excited states has enabled highly sensitive detection of metal ions, small molecules, explosives, volatile compounds, and biologically relevant analytes. Beyond sensing, we discuss emerging applications in catalysis, optoelectronics, bioprotection, and photonic materials, emphasizing how extended framework architectures facilitate substrate transport, active-site accessibility, and synergistic interactions between inorganic and organic building units. Ultimately, this Review seeks to move beyond a descriptive catalog of structures and applications to address a broader scientific question: how does reticularization fundamentally alter the behavior of atomically precise Ag NCs? By examining Ag NCMOFs through the interconnected lenses of nanochemistry, reticular chemistry, photophysics, and condensed-matter science, we aim to illuminate how periodic organization transforms discrete molecular emitters into collective functional materials and how this transformation is shaping a new generation of luminescent and sensing platforms.

2. Reticularization of Silver Nanoclusters

2.1. Structural Diversity of Ag Cluster Nodes

The smallest structurally defined Ag NCMOFs already reveal how reticularization can transform low-nuclearity Ag NCs into extended architectures with unexpected connectivity. In the Ag₄-based framework, the node is a compact Ag₄(I) unit stabilized by tert-butyl acetylide and trifluoroacetate ligands, while pyrazine serves as the external bridging linker (Figure a). Unlike larger thiolate-protected Ag clusters, this Ag₄ motif is not simply stitched into a network by the N-donor linker alone. The trifluoroacetate ligands actively participate in framework propagation, generating Ag₄–O–Ag₄ and Ag₄–O–C–O–Ag₄ linkages that first organize the clusters into 1D inorganic chains. These chains are then cross-connected by pyrazine linkers into a 3D framework. Thus, this material represents an instructive low-nuclearity case in which auxiliary carboxylate ligands and neutral N-donor linkers cooperate to convert a small Ag cluster into a spatially extended crystalline lattice. In contrast, the Ag₅ analogue from the same study demonstrates how a slight increase in cluster nuclearity and stoichiometric balance redirects the assembly into a different dimensional regime. The Ag₅ node is protected by tert-butyl acetylide and trifluoroacetate ligands and contains closely spaced Ag­(I) centers engaged in argentophilic interactions. These Ag₅ units organize into zigzag silver-rich chains, which are further joined by pyrazine linkers to produce a 2D sheet. The resulting framework therefore differs from the Ag₄ material not merely in atom count, but in architectural logic: the Ag₅ cluster itself supplies a continuous argentophilic backbone, whereas pyrazine expands this metallic chain laterally into a 2D reticular plane. This comparison is especially valuable because both frameworks arise from the same ligand/linker pool, showing that small changes in Ag nuclearity and precursor ratio can switch the assembly pathway from carboxylate-assisted 3D growth to argentophilic-chain-based 2D organization. Another structurally distinctive Ag₅ framework was reported in a chiral system built from R/S-tert-butyl-3-mercaptopyrrolidine-1-carboxylate-protected Ag₅ clusters. Here, the Ag₅S₆ unit (Figure a) adopts a twisted triangular-bipyramidal silver core embedded within a chiral thiolate shell, giving each cluster an intrinsically handed local environment. Rather than using a conventional multitopic organic linker, the framework is assembled through Na⁺ coordination to carbonyl groups on adjacent Ag₅ units, producing a 2D chiral layer. The layers stack in an AA fashion to generate channel-containing supramolecular architectures, within which additional discrete Ag₅ clusters are ordered as guests. This example broadens the concept of Ag NCMOF reticularization: framework formation is not restricted to direct Ag–N linker bridges, but can also proceed through cation-mediated organization of chiral cluster nodes, hydrogen-bond reinforcement, and host–guest ordering of secondary cluster units. Between the low-nuclearity Ag₅ frameworks and the more geometrically defined Ag₈ node, the Ag₇ system offers a distinct reticular motif in which the cluster is generated directly from a nitrogen-rich linker rather than from a preformed thiolate- or chalcogenolate-protected nanocluster. Hydrothermal reaction of AgNO₃ with 1H-tetrazole-5-acetic acid (Figure l) affords [Ag₇(tza)₃(Htza)₂(H₂tza)­(H₂O)] _n , which crystallizes in the triclinic P1̅ space group as a dense 3D framework. The asymmetric unit contains seven independent Ag­(I) centers, three fully deprotonated tza^2– ligands, two mono-deprotonated Htza^– ligands, one neutral H₂tza ligand, and one coordinated water molecule, producing a multinuclear Ag₇ node through diverse Ag–N and Ag–O coordination environments. The tetrazole–carboxylate ligands act as compact multidentate connectors, using μ₄ coordination modes of the tetrazole ring together with carboxylate oxygen binding to fuse trigonal-planar, trigonal-pyramidal, and distorted trigonal-pyramidal Ag sites into a reinforced 3D net. Structurally, this material expands the Ag NCMOF family by showing that Ag-cluster reticularization can arise from dense heterocyclic coordination and protonation-state diversity, not only from ligand-protected silver chalcogenolate clusters stitched by external linkers.

2.

Structural repertoire of bidentate organic linkers used for the assembly of Ag NCMOFs.

1.

Representative silver nanocluster nodes underpinning Ag NCMOF architectures.

4.

Molecular design space of (a–j) tetradentate, and (k, l) multidentate organic linkers explored in Ag NCMOF chemistry.

The Ag₈ framework represents an early example in which a high-connectivity silver–sulfur cluster (Figure b) acts simultaneously as a structural node and an exposed metal-rich surface. The Ag₈ node is generated from thiourea-functionalized tripodal linkers (Figure h,i), where sulfur donors anchor the silver core and organize the surrounding ligand arms into paired bridging units. Each Ag₈ cluster behaves as a six-connected node, while the C ₃-symmetric thiourea-bearing tripodal strut expands the assembly into a 3D porous framework. Structurally, this material is important because the cluster is not a hidden inorganic joint; it is a geometrically organized cubic Ag₈S₁₂ silver–sulfur node whose surface remains chemically accessible within large channels. The Ag₉–AgTPyP framework introduces a porphyrinic reticular motif in which tower-like Ag₉ clusters are spatially separated by Ag-metalated tetra­(4-pyridyl)­porphyrin linkers. The Ag₉ node is protected by tert-butyl acetylide and trifluoroacetate ligands, with short Ag···Ag contacts consolidating the cluster core (Figure c). Each Ag₉ cluster functions as a four-connected node, and μ₄-AgTPyP linkers propagate the structure into a 2D sheet with AB stacking. This architecture is notable because it fuses two metal-containing componentsthe Ag₉ cluster node and the Ag-centered porphyrin linkerwithin one ordered 2D lattice. The Ag₁₀ NCMOF developed by Mandal and co-workers is constructed by linking anionic [Ag₁₀( ^t BuS)₆(CF₃COO)₆]^2– cluster nodes with flexible 4,4′-trimethylenedipyridine (TMD, Figure i) spacers. At the heart of each node lies an Ag₁₀S₆ motif, in which a central rhombic Ag₄ fragment is flanked by two chair-shaped Ag₃S₃ units that are consolidated through both Ag–S coordination and argentophilic Ag···Ag interactions (Figure d). Acting as four-connecting inorganic vertices, the Ag₁₀ clusters are interconnected by TMD bridges to produce an extended 1D ladder-type reticular architecture. Beyond this primary connectivity, neighboring ladders assemble through directional AAAA and ABAB packing along orthogonal crystallographic axes, transforming the discrete 1D network into a three-dimensionally ordered supramolecular crystal. Distinct from the more symmetric silver cluster nodes described above, the Ag₁₁ building unit adopts an anisotropic Ag₁₁ framework featuring a distorted elongated square-bipyramidal geometry. The metallic core is stabilized by a mixed ligand environment comprising six adamantanethiolate ligands, four trifluoroacetate groups, and two terminally coordinated DMF molecules (Figure e), while linear 4,4′-azopyridine (Figure h) linkers provide the intercluster connectivity. Coordination of the pyridyl nitrogen atoms to neighboring Ag₁₁ nodes propagates the structure into a 1D channel-containing coordination array. Beyond the primary Ag–N linkage, the framework is reinforced through cooperative π···π stacking together with C–H···F and C–H···π contacts, leading to a 3D supramolecular packing arrangement in which nitrate anions are accommodated within the voids separating adjacent 1D chains.

3.

Representative tridentate organic linkers employed in the construction of Ag NCMOFs.

Among Ag NCMOFs, Ag₁₂-based architectures occupy a privileged position because the dodecanuclear silver core offers a rare balance between structural rigidity, accessible coordination vectors, and synthetic adaptability. The Ag₁₂ node can accommodate thiolate/chalcogenolate, carboxylate, solvent, and N-donor environments without losing its atomically defined identity, while its cuboctahedral or quasi-cuboctahedral geometry provides multiple peripheral Ag sites for reticular extension. This nuclearity is therefore large enough to behave as a true cluster-based SBU, yet compact enough to undergo linker-induced reorganization, symmetry modulation, and dimensional diversification. As a result, Ag₁₂ NCs have become the most recurrent and versatile lattice points in silver nanocluster reticular chemistry. The iconic Ag₁₂bpy framework established the structural blueprint for this field. The synthesis proceeds either through ligand exchange from a preformed acetonitrile-bound Ag₁₂ precursor or by a one-pot route in which 4,4′-bipyridine (Figure b) is introduced during cluster formation. In the molecular precursor, the Ag₁₂S₆ core displays a three-tier Ag₅S₂–Ag₂S₂–Ag₅S₂ arrangement with terminal CH₃CN donors at six peripheral Ag sites; upon framework formation, these solvent ligands are replaced by bpy linkers, accompanied by reorganization of the cluster shell into an Ag₁₂S₈-based node containing μ₃-tert-butylthiolate, μ₂-trifluoroacetate, and bpy components. The resulting Ag₁₂bpy framework crystallizes in the tetragonal I4̅2m space group, where every Ag₁₂S₈ node is joined to four neighboring nodes through eight μ₂-bpy bridges, generating a double-layered 2D network in the ab plane with rectangular microporous channels. Structurally, this work is pivotal because it showed that Ag₁₂ clusters can survive ligand substitution, undergo controlled shell rearrangement, and emerge as periodically ordered framework vertices rather than collapsing into ill-defined silver aggregates. Building on this archetype, TUS 5 demonstrated how tritopic imidazolyl linkers can redirect Ag₁₂ reticularization into a higher-connectivity 2D lattice. The material was prepared through a two-step route involving synthesis of Ag₁₂ NCs followed by coordination assembly with 2,4,6-tri­(1H-imidazol-1-yl)-1,3,5-triazine (THIT). Its Ag₁₂ node adopts a three-layered cuboctahedral arrangement composed of a central Ag₆ belt and two Ag₃ triangular caps, enclosed by μ₄-tert-butylthiolate and μ₂-trifluoroacetate ligands. Crystallizing in the trigonal P3 space group, the framework can be viewed as a (3,6)-connected 2D net in which each THIT linker binds three Ag₁₂ nodes while each Ag₁₂ node radiates toward six linkers. The layers stack through interlayer noncovalent interactions, giving open channels perpendicular to the 2D sheets. TUS 6 and TUS 7 provide a clean comparison of how tritopic linker geometry alters dimensionality while the Ag₁₂ node remains compositionally conserved. Both were synthesized by assembling Ag₁₂ nodes with three-connected pyridyl linkers, but the flexible tris­(pyridine-4-ylmethyl)­amine linker in TUS 6 generates a 3D (3,6)-connected framework, whereas the more elongated and π-conjugated 1,3,5-tris­(pyridine-4-ylethynyl)­benzene linker (Figure d) in TUS 7 gives a 2D architecture. In both cases, the Ag₁₂ nodes are protected by tert-butylthiolate and trifluoroacetate ligands, with pyridyl coordination sites extending from the cluster surface into the framework. The key structural lesson is that linker conformation controls whether the six accessible Ag coordination vectors are consumed within a plane or projected into 3D space. This pair therefore illustrates reticular dimensionality control without changing the metal-cluster nuclearity. TUS 8 represents a more compact Ag₁₂ architecture in which a short ditopic linker creates a robust layered network. It is constructed from dodecanuclear Ag₁₂ nodes and 1,1′-sulfonyldiimidazole (SDI) linkers (Figure d), with single-crystal analysis assigning the material to the monoclinic P2₁/c space group. The Ag₁₂ core is a slightly distorted hollow cuboctahedron capped by μ₄-tert-butylthiolate and μ₂-trifluoroacetate ligands (Figure f), while the imidazole termini of SDI provide the Ag–N connections needed for reticular growth. Topologically, the framework is best described as a (2,4)-connected 2D network, where compact linkers stitch Ag₁₂ vertices into crystalline sheets. These sheets are further organized through noncovalent contacts, giving a porous layered solid whose stability originates from both cluster-shell protection and tight interlayer packing. Another Ag₁₂ family using the 4,8-ethenobenzo-[1,2-c:4,5-c′]­dipyrrole-1,3,5,7­(2H,6H)-tetrone (BDI) linker

(Figure n) highlights how synthetic conditions can reroute the same Ag₁₂ chemistry into multiple coordination-polymer architectures. By varying reaction method and solvent, three related Ag₁₂–BDI structures were obtained, including a 1D cyclic-loop chain, a 2D layered material, and a two-fold interpenetrated loop-based architecture. In these materials, the Ag₁₂ node adopts a hollow cuboctahedral geometry, with ⁱ PrS^– and CF₃COO^– ligands defining the primary cluster shell while BDI acts as the external reticular linker. The structures crystallize in different monoclinic space groups, including C2/m, P2₁/m, and P2₁/c, reflecting how subtle changes in coordination propagation alter global symmetry. This series is useful because it shows that Ag₁₂ NCMOFs are not dictated only by linker identity; crystallization pathway and solvent environment can also steer topology. Ag₁₂bpy-2 introduced the idea that Ag₁₂ nodes can undergo nuclearity-retaining isomerization inside an extended framework. Starting from the original Ag₁₂bpy motif, the authors accessed a distinct Ag₁₂ framework formulated as [(Ag₁₂(SBu ^t )₆(CF₃COO)₆(bpy)₃)] _n , in which the same Ag count and ligand families are preserved but the cluster geometry and linker count are rearranged. The new node supports a trigonal structural motif rather than the tetragonal arrangement of Ag₁₂bpy, demonstrating that Ag₁₂ reticular chemistry can access structural isomers rather than merely compositional variants. Mixed-linker construction with amino-substituted bipyridine then generated Ag₁₂bpy-2/NH₂, while solvent-assisted linker exchange produced core–shell Ag₁₂bpy-2@Ag₁₂bpy-NH₂-2 crystals. Structurally, this work is significant because it treats the Ag₁₂ node as a reorganizable reticular unit whose metal arrangement, linker environment, and spatial distribution can all be programmed. The Ag₁₂bpa/Ag₁₂bpe study further shows how linker flexibility controls Ag₁₂ framework stability and transformation. Two isostructural 2D Ag₁₂ NCMOFs were obtained by connecting dodecanuclear silver chalcogenolate nodes with either 1,2-bis­(4-pyridyl)­ethane (bpa, Figure f) or 1,2-bis­(4-pyridyl)­ethylene (bpe, Figure g). Although both linkers are ditopic N-donors, the saturated bpa linker and unsaturated bpe linker impose different conformational constraints on the Ag₁₂-based lattice. Upon acetonitrile stimulation, Ag₁₂bpa transforms into a 1D Ag₁₀bpa framework through loss of two Ag atoms and reorganization of the remaining metal skeleton, whereas Ag₁₂bpe evolves into another 2D Ag₁₂ phase with distorted cluster nodes and altered topology. This work is structurally valuable because it captures Ag₁₂ NCMOFs not as static crystals but as dynamic cluster frameworks whose dimensionality and nuclearity can be reshaped by linker flexibility and solvent coordination. The SCC hybrid membrane study represents a processability-oriented extension of Ag₁₂ reticular chemistry rather than a conventional single-crystal NCMOF. In this strategy, silver chalcogenolate clusters are first organized into an assembled material and then covalently cross-linked to generate a membrane-like hybrid architecture. The structural idea is different from classical Ag–N coordination reticulation: instead of building a framework solely through crystalline linker propagation, the cluster assembly is chemically locked into a macroscopic, processable form. This example is therefore useful as a reminder that reticularization of Ag₁₂ clusters can move beyond single crystals toward extended cluster networks with membrane-level continuity. Chiral Ag₁₂ cluster frameworks add another layer of structural complexity by using the cluster itself as a stereochemical transmitter. In these materials, predesigned chiral Ag₁₂ clusters are assembled with pyridyl-type linkers (Figure m) into crystalline 2D chiral MOFs, while chiral camphorsulfonate-derived environments help encode handedness into the cluster framework. The Ag₁₂ units are connected into layered architectures in which the linkers adopt quasi-parallel arrangements, allowing chirality to propagate from the nanoscale cluster node into the extended lattice. The structures crystallize in chiral triclinic P1 symmetry, emphasizing that Ag₁₂ nodes can serve not only as geometric vertices but also as symmetry-defining elements. This work expands Ag₁₂ reticularization from topology control to handed framework construction. Ag₁₂TPPA illustrates how layer stacking can become an intrinsic structural variable in Ag₁₂ NCMOFs. A one-pot synthesis using tris­(4-pyridylphenyl)­amine (TPPA) (Figure c) links Ag₁₂ chalcogenolate nodes into a flexible 2D framework initially adopting an AA stacking arrangement. The Ag₁₂ nodes are surrounded by tert-butylthiolate and trifluoroacetate ligands, while six TPPA linkers bridge each cluster into an extended porous sheet. Partial escape of DMAc guest molecules drives layer sliding, converting the kinetic AA phase into more closely packed AB and ABC stacking variants. Thus, this system shows that Ag₁₂ NCMOFs can retain their 2D connectivity while reorganizing their interlayer registry, producing distinct crystalline phases through supramolecular layer motion. Ag₁₂CPPP demonstrates how a rigid tetratopic chromophoric linker can convert Ag₁₂ nodes into a deeply interpenetrated 3D architecture. The material was obtained by a one-pot reaction in mixed DMAc/CHCl₃/MeOH solvent using CPPP, a linker bearing both pyridyl and nitrile donor sites (Figure d). The Ag₁₂ node consists of 12 Ag­(I) atoms protected by six tert-butylthiolate and six trifluoroacetate ligands; four CPPP linkers bind through pyridyl donors and four additional CPPP units coordinate through nitrile groups. Crystallographic analysis assigns the framework to the I2/m space group and reveals a two-fold self-interpenetrated 3D net with 4,8-connected topology. This structure is notable because it introduced nitrile coordination as an additional reticular handle for Ag₁₂ cluster assembly. The tppe-based Ag₁₂/Ag₈ framework broadens the Ag₁₂ family by introducing heterocluster reticulation. Single-crystal analysis showed a triclinic P-1 framework containing both Ag₁₂ and Ag₈ chalcogenolate clusters connected by tetrakis­(4- pyridylphenyl)­ethene (tppe) linkers (Figure e). The Ag₁₂ and Ag₈ nodes are each stabilized by tert-butylthiolate and trifluoroacetate ligands, while tppe supplies multiple pyridyl donors and conformationally flexible aromatic arms. Rather than producing a single-node net, this assembly forms a dual-node 3D framework with two-fold interpenetration and large cages occupied by solvent molecules. Structurally, it demonstrates that Ag₁₂ nodes can coexist with lower-nuclearity silver clusters within one reticular lattice, expanding the concept of Ag NCMOFs toward heteronuclear cluster-node frameworks. The cucurbit[6]­uril-containing BPHF@CB[6] systems show how supramolecular linkers can be incorporated into Ag₁₂ reticular chemistry. In SCM 1–3, the BPHF@CB[6] host–guest adduct behaves as a preorganized bidentate linker, connecting Ag₁₂ cluster nodes through Ag–N coordination while the cluster shell is adjusted by arylthiolate or isopropylthiolate ligands together with methanesulfonate or trifluoroacetate anions. SCM 1 forms a monoclinic P2/c wave-like 1D chain through coordination at asymmetric Ag sites, whereas SCM 2 adopts a monoclinic P2₁/n linear 1D arrangement using more symmetric coordination positions and a distinct trifluoroacetate binding pattern. SCM 3 retains the one-dimensional linkage motif but replaces the arylthiolate environment with ⁱ PrS^– ligands and crystallizes in triclinic P1̅ symmetry. This family is especially attractive from a structural perspective because the “linker” is not a simple organic strut but a supramolecular object whose cucurbituril sheath changes steric volume, packing, and coordination presentation around the Ag₁₂ lattice.

Moving beyond the highly recurrent Ag₁₂ node, higher-nuclearity Ag NCMOFs reveal how small changes in silver count can generate entirely new metal skeletons, ligand-shell arrangements, and framework connectivities. The Ag₁₃-based TUS 9 marks an instructive transition from compact polyhedral nodes to an anisotropic cluster core. It was obtained by first generating a mixed thiolate–trifluoroacetate Ag­(I) cluster environment from [AgS ^t Bu] _n and CF₃COOAg in acetonitrile/ethanol, followed by slow crystallization with 3,6-di­(4-pyridyl)-1,2,4,5-tetrazine (Figure j) at 273 K. The inorganic unit is a bow-shaped Ag₁₃ core in which a central Ag2–Ag2 crown, basal Ag vertex, and two laterally extended Ag3–Ag2–Ag4 wings are held together by argentophilic contacts. Ten tert-butylthiolate ligands and three trifluoroacetate anions envelop the curved metal skeleton, giving a mixed sulfur/oxygen coordination shell that stabilizes the non-closed Ag₁₃ geometry while leaving peripheral Ag sites available for Ag–N reticulation (Figure g). The first Ag₁₄ example in this series, ACAM-1, shows how replacing thiolate protection with alkynyl ligation can unlock metal-node geometries rarely accessible in conventional Ag–S cluster chemistry. This 2D material, formulated as [Ag₁₄(CF₃COO)₆( ^t BuCC)₈(pyz)₂], crystallizes in centrosymmetric P1̅ symmetry and contains two crystallographically distinct Ag₁₄ nodes within the same lattice. One node is built from staggered pentagonal-pyramidal Ag₆ fragments joined through a quadrilateral Ag subunit, whereas the other is assembled from a central octahedron flanked by two distorted octahedral fragments. Both nodes are protected by tert-butylacetylide and trifluoroacetate ligands and are connected by pyrazine linkers into alternating 2D sheets, producing an unusual single-crystal framework in which two different Ag₁₄ geometries coexist in an ordered reticular pattern. A different Ag₁₄ design principle was introduced through carborane-dithiolate-protected superatomic clusters. In this case, slow crystallization of CF₃COOAg with 1-thiol-o-carborane generates an fcc-type Ag₁₄ superatom protected by six face-capping 1,2-dithiolate-o-carborane ligands, while labile acetonitrile groups occupy the vertex positions. Replacement of these weakly bound donors by ditopic N-linkers enabled a dimensional series: pyrazine gives a 1D helical SCAM-1 in trigonal P3₂, dipyridin-4-yl-diazene affords a 2D grid SCAM-2 in monoclinic C2/m, 4,4′-bipyridine generates a 3D bcu-type SCAM-3 in tetragonal P4mn/c, and 1,4-bis­(4-pyridyl)­benzene produces a two-fold interpenetrated 3D SCAM-4 in tetragonal I4₁/a. The structural elegance of this family lies in its site-specific assembly logic: the Ag₁₄ core is preserved, while the external linker length and geometry determine whether the superatomic nodes organize as helices, sheets, open 3D nets, or interwoven frameworks. Chiral Ag₁₄ frameworks further demonstrate that Ag NCMOF formation can be used to control not only dimensionality but also handedness. Racemic Ag₁₄(SPh­(CF₃)₂)₁₂(PPh₃)₄(DMF)₄ clusters, whose distorted fcc silver cores are protected by bulky thiolate and phosphine ligands, contain four weakly coordinated DMF molecules arranged as replaceable surface donors. Bottom-up assembly with enantiopure bis­(pyridyl-imine) cyclohexane linkers LR or LS (Figure k,l) replaces these DMF ligands and converts the racemic cluster pool into homochiral 3D frameworks Ag₁₄-LR and Ag₁₄-LS, both crystallizing in the chiral P6₅22 space group. Each Ag₁₄ node is connected to four neighboring clusters through four bidentate linkers, giving a twisted tetrahedral expansion around the cluster. When racemic LRS is used instead, the framework crystallizes in orthorhombic Pnnn symmetry and adopts an achiral diamond-like topology containing alternating R-Ag₁₄ and S–Ag₁₄ nodes. The chloride-templated Ag₁₄/Ag₁₅ system provides a particularly clear demonstration of nuclearity-controlled dimensionality. A one-pot reaction of [Ag–S ^t Bu] _n , CF₃COOAg, PPh₄Cl, and 4,4′-bipyridine in CH₃CN/DMF produces cluster frameworks in which the enclosed chloride anion guides construction of incomplete square-gyrobicupola silver skeletons. The Ag₁₅ framework, formulated as [Ag₁₅Cl­(S ^t Bu)₈(CF₃COO)_5.67(NO₃)_0.33(bpy)₂(DMF)₂]·4.3DMF·H₂O, crystallizes in triclinic P1̅ symmetry and forms a 1D ladder-like array through bpy bridges; its Ag₁₅ core (Figure i) contains eight tert-butylthiolates, partially disordered trifluoroacetate/nitrate auxiliary ligation, and two coordinated DMF molecules. Under a different precursor ratio, further removal of one silver atom gives the Ag₁₄ framework [Ag₁₄Cl­(S ^t Bu)₈(CF₃COO)₅(bpy)₂(DMF)]·2DMF, also triclinic P1̅, where Ag₁₄ nodes (Figure h) are fourfold connected by bpy into a 2D hcb layer. Thus, a single templating strategy maps a subtle Ag₁₆ → Ag₁₅ → Ag₁₄ nuclearity contraction onto a dimensional sequence from isolated cluster to 1D framework to 2D sheet.

The Ag₁₆-TPyP pair illustrates how solvent-programmed surface substitution can generate different frameworks from nearly identical cluster and linker components. The synthesis can proceed either stepwise from Cl@Ag₁₆ precursors or by one-pot assembly of AgS ^t Bu, CF₃COOAg, HCl, and tetra­(4-pyridyl)­porphyrin (TPyP) under solvent control. Both Ag₁₆ precursors contain a chloride-centered Ag₄S₄–Ag₈Cl–Ag₄S₄ skeleton resembling a square gyrobicupola, protected by μ₄-tert-butylthiolates, trifluoroacetates, and weakly coordinated solvent molecules. Coordination with TPyP gives 2D-Ag₁₆-TPyP, crystallizing in triclinic P1̅, and 3D-Ag₁₆-TPyP, crystallizing in monoclinic C2/c. In the 2D phase, coplanar Ag–N junctions connect Ag₁₆ nodes and porphyrin linkers into AB-stacked sql sheets, whereas in the 3D phase staggered Ag–N connection vectors rotate the porphyrin planes and extend the same node–linker pair into a pts-type 3D framework. The Ag₁₈BDC/Ag₁₈FBDC pair expands the Ag NCMOF family into carboxylate-linked alkynyl-protected clusters. These materials are synthesized from tert-butylacetylide silver precursors, dichromate-derived chromate templates, silver trifluoroacetate, and either BDC (Figure o) or fluorinated FBDC (Figure p) under solvothermal conditions. Single-crystal X-ray diffraction (SCXRD) assigns Ag₁₈BDC to monoclinic C2/c and Ag₁₈FBDC to triclinic P1̅; both contain a [(CrO₄)@Ag₁₈( ^t BuCC)₁₂] cluster core in which the encapsulated chromate anion anchors the silver shell through Ag–O contacts. The Ag₁₈ polyhedron contains triangular, tetragonal, and pentagonal faces, with 12 tert-butylacetylide ligands capping triangular faces and four dicarboxylate linkers defining pentagonal windows (Figure j). Each Ag₁₈ node connects to four neighboring nodes through BDC or FBDC linkers, producing 2D 4-connected sql layers while preserving exposed silver-rich surface regions. The Ag₂₀ systems show how high-nuclearity silver clusters can serve as chiral reticular nodes without relying on chiral linkers. The parent R/S-Ag₂₀ clusters are synthesized from AgS ^t Bu and R/S-THF-COOAg in acetonitrile/DMF and crystallize in chiral monoclinic C ₂ symmetry. Their metal skeleton is a carbonate-templated drum-like Ag₂₀S₁₀ architecture composed of two Ag₅S₅ pentagram layers and a central Ag₁₀ ring, protected by μ₄-tert-butylthiolates, chiral tetrahydrofuran carboxylates, and coordinated DMF molecules (Figure k). Replacement of the DMF donors with 4,4′-bipyridine or amino-functionalized bipyridine produces R/S-Ag₂₀bpy and R/S-Ag₂₀bpy-NH₂, which crystallize in chiral P2₁ symmetry. Both frameworks retain the Ag₂₀S₁₀ skeleton and form chiral (2,4)-connected 2D sql layers, showing that the local handedness of a cluster node can be transferred into an extended reticular sheet using achiral linear linkers.

The transition from medium-sized Ag cluster nodes to giant Ag NCMOFs begins with Ag₂₇-MOF, where the silver cluster no longer behaves as a compact polyhedral vertex but as a broad metallic platform embedded in a 2D lattice. This framework was obtained by slow diffusion of a mother solution containing AgS ^t Bu and CF₃COOAg into a solution of 5,10,15,20-tetra­(4-pyridyl)­porphyrin, yielding crystals of {Ag₂₇S₂( ^t BuS)₁₄(CF₃COO)₈(TPyP-H₂)} _n . SCXRD assigns the structure to the orthorhombic Cmcm space group and reveals a C _2ν-symmetric saddle-shaped Ag₂₇ node templated by two internal sulfide ions and protected by 14 tert-butylthiolate and eight trifluoroacetate ligands (Figure l). Only four corner Ag sites coordinate to the pyridyl arms of TPyP-H₂, allowing both the Ag₂₇ cluster and porphyrin linker to behave as four-connected nodes in a 2D sql net. These sheets are further organized through C–H···F and C–H···π contacts along the b direction, converting the primary 2D coordination array into a three-dimensionally packed supramolecular solid. Ag₅₄-based ZZU-601 represents a further escalation in cluster size, where anion templation rather than simple linker coordination dictates the formation of the silver node. The material, [(HPO₄)₄(H₂PO₄)₂@Ag₅₄( ⁱ PrS)₃₂(CF₃COO)₆(CH₃CN)₂(H₂TCPP)­(TCPP)] _n , is generated using phosphate species as internal templates together with isopropylthiolate ligation and carboxylate-functionalized porphyrin linkers. Six phosphate-derived anions organize the silver atoms into an ellipsoidal Ag₅₄ cluster, which is then stabilized by thirty-two ⁱ PrS^– ligands, trifluoroacetate auxiliaries, and terminal solvent donors (Figure m). Two crystallographically distinct TCPP linkers (Figure i) connect the Ag₅₄ nodes vertically and laterally, giving a 3D framework that can be simplified as a 4,8-connected scu-type net. The architecture is additionally double-interpenetrated, showing that very large Ag nodes can generate high-connectivity frameworks while simultaneously reducing accessible void space through framework weaving. Ag₇₂ NCMOFs push reticular silver- cluster chemistry into a still larger regime through structural transformation rather than direct one-pot assembly. In the precursor stage, a lacunary Keggin polyoxometalate, PW₉O₃₄ ^9–, templates a single-pod Ag₅₁ cluster in methanol/DMF; subsequent reaction with bipyridyl linkers fuses two such pod-like units into a peanut-shaped [(PW₉O₃₄)₂@Ag₇₂] node (Figure n). For SD/Ag72a, 4,4′-bipyridine links the transformed Ag₇₂ nodes into a monoclinic P2₁/n 2D 4⁴-sql layer, with the Ag₇₂ shell protected by ⁱ PrS^–, CF₃COO^–, bipy, methanol, and water ligands. The Ag₇₂ node itself consists of two unequal silver hemispheres around two preserved PW₉O₃₄ ^9– templates, with an equatorial sulfide-centered Ag₁₂ plane acting as the junction between the two pods. Replacement of bipy with 1,4-bis­(4-pyridinylmethyl)­piperazine produces SD/Ag72c, in which each Ag₇₂ node connects to six neighbors through pi-bipy bridges to generate a 3D pcu framework, demonstrating that linker length and flexibility can redirect the same giant cluster node from a layered net to a fully 3D lattice.

2.2. Architectural Evolution and Dimensional Diversification of Ag NCMOFs

Reticularization of Ag NCs is not a simple act of connecting clusters; it is an architectural translation process in which the coordination vectors exposed on a ligand-protected silver cluster are converted into extended crystalline dimensionalities. The final framework is governed by a delicate balance among cluster nuclearity, surface ligand lability, auxiliary ligand participation, linker denticity, linker length, conformational freedom, and intercluster packing. Thus, identical or closely related Ag cluster cores can produce 1D chains, 2D sheets, 3D networks, interpenetrated frameworks, or ladder-type architectures depending on how the organic linker interrogates the cluster surface. This dimensional plasticity is one of the defining structural signatures of Ag NCMOFs, distinguishing them from conventional MOFs whose framework dimensionality is often dictated mainly by fixed metal-node geometry.

A clear illustration of linker-controlled dimensional diversification is provided by three Ag NCMOFs constructed from AgS ^t Bu, CF₃COOAg, and pyridyl linkers through slow evaporation. In Ag₁₀hpbt, the Ag₁₀S₆ node is supported by tert-butylthiolate and trifluoroacetate ligands and connected by the hexapyridyl (hpbt) linker (Figure k), whose six pyridyl donors distribute coordination demand around the cluster surface. The Ag₁₀ node therefore behaves as a six-connected reticular vertex, and the highly multitopic linker expands the assembly into a 3D framework crystallizing in the monoclinic C2/c space group (Figure a). By contrast, Ag₁₂bpva uses a more elongated anthracene-based ditopic linker, bpva (Figure m), to connect cuboctahedral Ag₁₂ nodes into a monoclinic P2₁/n 2D net, showing how linker extension and π-rigidity can flatten Ag₁₂ connectivity into a sheet-like architecture (Figure b). The third member, Ag₁₂bpb, also crystallizes in monoclinic P2₁/n symmetry but adopts a 1D chain because the shorter bpb linker and solvent-coordinated Ag₁₂ node restrict the number of productive Ag–N junctions (Figure c); together, these three structures demonstrate a rare 3D → 2D → 1D dimensional sequence generated by changing linker geometry while retaining silver–thiolate/carboxylate cluster chemistry.

5.

Hierarchical reticular evolution of Ag NCMOFs, illustrating the transformation of discrete Ag NCs into extended crystalline architectures through sequential surface functionalization, ancillary ligand incorporation, and linker-directed coordination assembly. Representative framework motifs derived from Ag NC nodes include (a) 3D Ag₁₀hpbt, (b) 2D Ag₁₂bpva, and (c) 1D Ag₁₂bpb, where cluster nodes are depicted as polyhedral building units. H atoms are excluded for clarity. Adapted with permission from ref . Copyright 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH. (d) 2D–3D interpenetrated Ag₁₂ nanocluster framework. Adapted with permission from ref . Copyright 2025, The Author(s). (e) Construction of a ladder-like Ag₁₃ nanocluster architecture through longitudinal cluster propagation mediated by metallophilic and ligand-assisted interactions (rails), followed by transverse linkage of neighboring chains through tetrazine spacers (rungs), yielding a periodically organized ladder topology. Adapted with permission from ref . Copyright Creative Commons Attribution 3.0 Unported license.

The Ag₁₂–TCNB system pushes dimensional diversification further by showing that two framework dimensionalities can coexist within a single crystal rather than appearing as separate phases. In SC-1, the same Ag₁₂ cluster platform is connected by tetracyanobenzene linkers in two distinct coordination modes: one set of TCNB linkers generates a 2D network, whereas another set extends Ag₁₂ nodes into a 3D framework. The result is a 2D–3D interpenetrated Ag NCMOF, in which a lower-dimensional net and a higher-dimensional framework occupy the same crystalline volume like two woven structural logics (Figure d). This is conceptually important because interpenetration here is not merely a packing consequence of identical nets; it is a dimensional hybrid, where different Ag_12–TCNB connectivities create different reticular sublattices. Upon photoinduced loss of weakly bound trifluoroacetic acid and partial TCNB occupancy, this 2D–3D architecture reorganizes into a 3D–3D interpenetrated form, whereas prolonged crystallization gives a noninterpenetrated 3D framework, revealing that Ag NCMOF dimensionality can be dynamically rewritten by vacancy formation, linker occupancy, and crystal-growth history.

A still different architectural language appears in the ladder-type Ag₁₃ framework TUS 9. Unlike classical Ag NCMOFs built from isolated cluster nodes connected isotropically by linkers, TUS 9 first organizes bow-shaped Ag₁₃ clusters into extended 1D cluster chains through metal–metal contacts and ligand-mediated propagation. These parallel Ag₁₃ chains then serve as longitudinal rails, while rigid 3,6-di­(4-pyridyl)-1,2,4,5-tetrazine linkers laterally bridge neighboring chains as molecular rungs, locking the material into a monoclinic C2/c ladder framework (Figure e). This cluster–chain–ladder hierarchy introduces an intermediate level of reticular organization between discrete-node frameworks and fully 2D sheets: the primary structural object is not a single cluster but a prealigned cluster strand. The resulting architecture shows that dimensionality in Ag NCMOFs can be built hierarchically, with 1D cluster propagation preceding transverse linker stitching; in such systems, linker rigidity controls not only connectivity but also interchain registry, rail spacing, and the formation of narrow microporous voids between the ladder elements.

These examples show that Ag NCMOF architecture evolves through several distinct dimensional pathways. Multitopic linkers such as hpbt can project cluster connectivity into 3D space; rigid π-extended ditopic linkers such as bpva can enforce 2D sheet formation; shorter or more sterically constrained linkers such as bpb can reduce the framework to 1D chains; tetracyanobenzene can generate interpenetrated architectures with mixed dimensional identity; and tetrazine linkers can convert preformed cluster chains into ladder-type frameworks. Therefore, dimensionality in Ag NCMOFs should not be regarded as a passive crystallographic outcome. It is a programmable structural variable encoded jointly by cluster surface chemistry, linker directionality, coordination-site accessibility, and supramolecular packing. Representative Ag NCMOFs discussed in this section are summarized in Table according to cluster nuclearity, principal reticular connectivity, framework dimensionality, and key structure–function characteristics.

1. Representative Ag NCMOFs, Their Structural Characteristics, and Key Functionalities Discussed in This Review.

Representative Ag NCMOF	Cluster nuclearity	Principal linker/connecting motif	Framework dimensionality/architecture	Key functionality or structure–function feature	refs
Ag4–pyrazine framework	Ag4	Pyrazine + CF3COO–-assisted intercluster connectivity	3D; carboxylate-assisted 1D Ag4 chains cross-linked by pyrazine	Illustrates cooperative participation of auxiliary carboxylates and N-donor linkers in converting a low-nuclearity Ag cluster into a 3D reticular lattice
Ag5–pyrazine framework	Ag5	Pyrazine; argentophilic Ag···Ag chain propagation	2D sheet	Demonstrates nuclearity-dependent dimensional control; Ag···Ag-connected zigzag chains are expanded laterally by pyrazine
Chiral Ag5 framework	Ag5	Chiral thiolate shell; Na+-mediated carbonyl coordination	2D chiral layers with AA stacking	Transfers cluster-level chirality into an extended architecture; demonstrates cation-mediated reticularization and host–guest ordering of Ag5 units
Ag7–tza framework	Ag7	Tetrazole–carboxylate coordination	3D dense framework	Demonstrates linker-generated multinuclear Ag nodes through diverse Ag–N/Ag–O coordination and protonation-state-controlled connectivity
Ag8 framework	Ag8	Thiourea-functionalized tripodal linker	3D porous framework; six-connected Ag8 node	Provides an accessible Ag-rich surface within large channels; illustrates integration of high-connectivity Ag–S nodes with porous reticular architecture
Ag9–AgTPyP	Ag9	Ag-metalated tetra(4-pyridyl)porphyrin	2D sheets with AB stacking	Integrates an Ag9 cluster and a metalated porphyrinic linker within the same lattice, providing a platform for cluster–chromophore electronic coupling
Ag10–TMD	Ag10	4,4′-Trimethylenedipyridine	1D ladder with 3D supramolecular packing	Demonstrates flexible-linker-directed ladder formation and cooperative argentophilic/Ag–S stabilization
Ag11–azopyridine	Ag11	4,4′-Azopyridine	1D channel-containing array with 3D supramolecular packing	Illustrates anisotropic cluster-node propagation reinforced by π···π and other noncovalent interactions
Ag12bpy	Ag12	4,4′-Bipyridine	2D, double-layered microporous framework	Archetypal Ag NCMOF; framework rigidification improves oxidation/photodegradation resistance and luminescence efficiency; foundational platform for cluster-based photophysics
TUS 5 (Ag12–THIT)	Ag12	Tritopic THIT	2D (3,6)-connected framework	Demonstrates increased reticular connectivity through tritopic linker design and formation of open channels perpendicular to the sheets
TUS 6	Ag12	Tris(pyridine-4-ylmethyl)amine	3D (3,6)-connected framework	Demonstrates linker-conformation-controlled projection of Ag coordination vectors into three dimensions
TUS 7	Ag12	1,3,5-Tris(pyridine-4-ylethynyl)benzene	2D framework	Shows that rigid, π-conjugated linker geometry can confine the same Ag12 coordination vectors within a plane
TUS 8	Ag12	Sulfonyldiimidazole	2D (2,4)-connected layered framework	Water-compatible luminescent sensing of antibiotics with analyte-dependent spectral fingerprints
Ag12–BDI family	Ag12	BDI linker	1D/2D/interpenetrated architectures	Demonstrates solvent- and crystallization-dependent dimensional diversification while preserving Ag12 cluster chemistry
Ag12bpy-2/derivatives	Ag12	Bipyridine/amino-bipyridine	Reticular Ag12 structural isomers	Demonstrates nuclearity-retaining cluster isomerization, mixed-linker programming, and spatially controlled linker exchange
Ag12bpa/Ag12bpe	Ag12	bpa or bpe	2D parent frameworks; stimulus-responsive transformation	Demonstrates solvent-triggered framework reconstruction; Ag12bpa can transform into 1D Ag10bpa through nuclearity and dimensionality change
Chiral Ag12 framework	Ag12	Pyridyl linker + chiral cluster environment	2D chiral framework	Propagates cluster-level handedness into an extended crystalline lattice; cluster node acts as a stereochemical transmitter
Ag12TPPA	Ag12	TPPA	2D; AA → AB/ABC stacking variants	Guest-loss-induced layer sliding and control of interlayer registry; demonstrates dynamic stacking as a structural variable
Ag12CPPP	Ag12	Pyridyl/nitrile-containing CPPP	3D, 2-fold self-interpenetrated; 4,8-connected	Demonstrates nitrile coordination as an additional reticular handle and formation of an interpenetrated cluster–chromophore network
Ag12/Ag8–TPPE	Ag12 + Ag8	TPPE	3D, dual-node, 2-fold interpenetrated	Heterocluster reticulation; mesoporous host–guest photophysics and dye encapsulation can generate dual emission/white-light output
Ag12–TCNB	Ag12	Tetracyanobenzene	2D–3D/3D–3D interpenetrated, stimulus-transformable	Photo-/guest-responsive structural reconfiguration, conductivity modulation, and moisture recognition through water-induced structural transformation and luminescence color change	,
Ag10hpbt	Ag10	Hexapyridyl hpbt	3D	Demonstrates multitopic-linker-driven high-dimensional assembly; photoluminescent sensing platform for nitrobenzene
Ag12bpva	Ag12	Anthracene-based bpva	2D	π-Rigid linker flattens cluster connectivity into a sheet; photoluminescent sensing platform for nitrobenzene
Ag12bpb	Ag12	Short ditopic bpb	1D	Restricted Ag–N connectivity generates a 1D chain; photoluminescent sensing platform illustrating dimensionality-dependent optical behavior
TUS 9	Ag13	3,6-Di(4-pyridyl)-1,2,4,5-tetrazine	1D ladder-type cluster–chain architecture	Selective luminescent recognition of basic amino acids through a tetrazine-rich recognition environment; reversible sensing
ACAM-1	Ag14	Pyrazine; alkynyl-protected Ag14 nodes	2D sheets	Contains two crystallographically distinct Ag14 geometries within one ordered lattice, demonstrating node-geometric diversity at constant nuclearity
SCAM-1–4	Ag14	Ditopic N-donor linkers of different length/geometry	1D → 2D → 3D dimensional series	Preserves the Ag14 superatom while linker geometry programs helices, grids, open 3D nets, and interpenetrated frameworks
Ag14-LR/Ag14-LS	Ag14	Enantiopure bis(pyridyl-imine) linkers	3D chiral framework	Enantioselective reticular assembly converts a racemic cluster population into homochiral frameworks
Ag15–bpy/Ag14–bpy	Ag15/Ag14	4,4′-Bipyridine; chloride templation	1D ladder/2D hcb layer	Demonstrates nuclearity-controlled dimensionality; subtle Ag-count contraction maps directly onto changes in framework dimensionality
Ag16–TPyP	Ag16	Tetra(4-pyridyl)porphyrin	2D sql or 3D pts	Solvent-programmed surface substitution changes coordination-vector orientation, allowing the same cluster/linker pair to generate distinct 2D and 3D frameworks
Ag18BDC/Ag18FBDC	Ag18	BDC/fluorinated BDC	2D, 4-connected sql layers	Heterogeneous Knoevenagel catalysis; linker fluorination increases the electropositive character of Ag sites and enhances Lewis-acid catalytic activity
R/S–Ag20bpy and R/S–Ag20bpy-NH2	Ag20	bpy/amino-bpy	2D chiral sql layers	Transfers intrinsic cluster chirality into the extended framework; temperature-dependent multicolor circularly polarized luminescence
Ag27-MOF	Ag27	TPyP-H2	2D sql framework	Exposed Ag-rich saddle surface provides accessible π-Lewis-acidic sites for CO2 carboxylative cyclization of propargylamines
ZZU-601	Ag54	TCPP; phosphate-templated cluster	3D, 4,8-connected scu-type, double-interpenetrated	Dual-functional catalytic platform for detoxification of chemical-warfare-agent simulants
SD/Ag72a	Ag72	4,4′-Bipyridine	2D sql framework	Demonstrates reticularization of a giant POM-templated Ag72 node and nuclearity enlargement from Ag51 precursor units
SD/Ag72c	Ag72	1,4-Bis(4-pyridinylmethyl)piperazine	3D pcu framework	Shows linker-length/flexibility-controlled conversion of the same giant Ag72 node from 2D to 3D connectivity

3. Photophysical Properties of Reticularized Silver Nanoclusters

3.1. Origin of Luminescence

The luminescence of reticularized Ag NCs originates from a delicate electronic dialogue between the Ag core, protecting ligands, bridging linkers, and the extended crystalline lattice. Unlike plasmonic Ag nanoparticles, whose optical response is dominated by collective electron oscillation, atomically precise Ag NCs behave as molecular emitters with discrete excited states. When these clusters are incorporated into reticular frameworks, their emission is no longer determined only by the isolated metal core. Instead, the emissive state becomes a hybrid object shaped by Ag···Ag interactions, Ag–S/Ag–N/Ag–O coordination, linker π orbitals, framework rigidity, and guest-accessible microenvironments. In many frameworks containing d¹⁰ Ag­(I) NCs, the lowest-energy emissive states are more appropriately described as cluster–linker charge-transfer states than as purely metal-centered excited states. , The Ag-rich core contributes filled 4d-derived orbitals and low-lying cluster-

centered electronic states, whereas pyridyl, cyano, porphyrin, BODIPY, tetraphenylethene, imidazole, and tetrazine linkers introduce donor and acceptor orbitals that reorganize the frontier electronic structure. As a consequence, photoexcitation may populate linker-to-metal charge-transfer (LMCT) states, metal-to-linker charge-transfer (MLCT) states, linker-centered singlet states, cluster-centered triplet states, or electronically mixed cluster–linker excited states, depending on the linker electronics, Ag···Ag separations, cluster nuclearity, and coordination geometry. ,− In several Ag₁₂-cluster frameworks, theoretical calculations reveal that absorption is dominated by LMCT transitions, whereas the observed visible emission originates primarily from MLCT-mediated excited-state relaxation, highlighting the bidirectional electronic communication that develops between the Ag NC node and the reticular linker network. This explains why two frameworks constructed from similar Ag₁₂ nodes can exhibit dramatically different emission wavelengths, lifetimes, quantum yields, and sensing responses when the linker identity, framework topology, or local chemical environment is altered.

From a general photophysical perspective, reticularization alters Ag NC excited states through three interconnected effects. First, framework formation rigidifies the cluster–ligand environment and suppresses vibrational, conformational, and structural relaxation pathways that otherwise promote nonradiative decay, thereby stabilizing emissive states and often increasing luminescence efficiency. Second, periodic organization establishes defined cluster–cluster separations and cluster–linker geometries, enabling Ag···Ag interactions, linker-mediated electronic communication, and energy- or charge-transfer pathways that are poorly controlled or absent in discrete clusters. Third, reticularization creates spatially defined pore microenvironments in which guest molecules can interact reproducibly with the emissive lattice, perturbing local polarity, coordination, framework conformation, or excited-state quenching pathways. Reticularization therefore does not simply immobilize Ag NCs within a crystalline scaffold; it reorganizes the energetic landscape through which excitation, relaxation, energy migration, and emission occur, converting molecular cluster photophysics into a framework-dependent collective property.

A central feature of reticularized Ag NCs is the strong participation of triplet excited states. The heavy-atom character of silver enhances spin–orbit coupling, facilitating intersystem crossing and enabling long-lived phosphorescence at room temperature or low temperature. In Ag₁₂bpy, oxygen-sensitive emission is associated with relatively long-lived cluster-centered excited states, which are efficiently quenched by triplet oxygen. In Ag₁₂bpy-NH₂, amino substitution on the bipyridine linker creates dual fluorescence–phosphorescence behavior, where a short-lived blue fluorescence acts as an internal reference and a long-lived yellow phosphorescence becomes oxygen-responsive. Thus, the linker does not merely connect clusters; it changes the probability with which singlet excited states cross into triplet manifolds.

Reticularization also suppresses nonradiative decay. − Isolated Ag NCs often lose emission through ligand vibration, core distortion, aggregation, oxidation, or solvent-induced decomposition. Once locked into a framework, these motions are restricted. , The cluster is spatially separated from neighboring emissive units, the ligand shell becomes less labile, and the crystalline lattice reduces conformational disorder. This “structural freezing” increases radiative efficiency, stabilizes excited states, and often enables luminescence that is weak or absent in the discrete precursor. The emergence of bright room-temperature emission from Ag₁₂-, Ag₁₄-, Ag₁₈-, and Ag₂₀-based frameworks therefore reflects not only the intrinsic photophysics of the cluster, but also the ability of the reticular scaffold to protect fragile excited states from structural dissipation. ,,,

3.2. Structure–Luminescence Relationships

The photophysical behavior of Ag NCMOFs is highly structure-dependent because the emissive state is sensitive to small changes in cluster nuclearity, metal–metal separation, ligand identity, coordination mode, framework dimensionality, and lattice flexibility. Among these parameters, Ag···Ag distance is especially important. Argentophilic interactions influence orbital overlap within the Ag core and can shift the balance between localized cluster emission and charge-transfer emission. Framework assembly can enhance intercluster electronic communication through argentophilic Ag···Ag interactions and linker-mediated conjugation, often resulting in red-shifted optical transitions, improved luminescence efficiency, and modified excited-state behavior. Conversely, structural distortion, ligand removal, or weakening of Ag···Ag contacts can quench emission or shift the spectral output.

The Ag₁₂bpy system illustrates the foundational structure–luminescence principle. Discrete Ag chalcogenolate clusters are chemically vulnerable and weakly emissive, but reticular connection through bipyridyl linkers transforms them into a stable porous luminophore with strong room-temperature emission. Here, the framework stabilizes the Ag₁₂ core, preserves open diffusion pathways, and creates uniform emissive sites. This relationship becomes more elaborate in flexible Ag₁₀bpy, where small chloromethane molecules induce different pore-opening states and guest orientations. CH₂Cl₂, CHCl₃, and CCl₄ do not merely enter the pores; they reorganize local dipoles, alter chromophore–guest contacts, and tune the emission color. The framework therefore behaves as a photophysical translator of molecular geometry.

Cluster nuclearity also matters. Ag₁₀, Ag₁₂, Ag₁₃, Ag₁₈, Ag₂₀, and Ag₂₇ frameworks do not simply represent larger or smaller versions of the same emitter. Each nuclearity creates a distinct metal orbital arrangement, coordination surface, and ligand-binding geometry. For example, Ag₁₈bpy-NH₂ exhibits mechanochromism and thermochromism because its 1D chain structure permits reversible packing changes and low-temperature activation of long-lived triplet emission. Ag_13‑based TUS 9, in contrast, uses bow-shaped Ag₁₃ chains and tetrazine bridges to generate a ladder-like architecture whose emission can be selectively quenched by basic amino acids. In this case, the cluster chain supplies the emissive scaffold, while the tetrazine linker provides both electronic modulation and recognition sites.

Dimensionality offers another powerful handle. A 1D chain, 2D sheet, and 3D framework made from similar clusters can display sharply different emission because the pathways for exciton migration, lattice relaxation, guest diffusion, and intercluster coupling differ. In low-dimensional architectures, the cluster nodes may remain more exposed and flexible, allowing stronger stimulus response. In highly connected 3D networks, the emissive centers are often more rigid and protected, giving improved photostability and stronger solid-state emission. Thus, dimensionality is not a passive structural descriptor; it determines whether the excited state remains localized, migrates through the lattice, couples with guests, or relaxes through framework motion.

3.3. Tunable Emission Behavior

One of the most attractive features of reticularized Ag NCs is that their emission can be tuned without changing the metal cluster alone. The color, lifetime, intensity, and response mode can be adjusted by linker electronics, substituent effects, guest inclusion, temperature, mechanical force, solvent coordination, and postsynthetic transformation. Linker engineering is the most direct route. Electron-rich linkers can raise donor-state energies and promote linker-to-metal or linker-centered emission, whereas electron-deficient linkers such as TCNB, tetrazine, nitroaromatic-responsive environments, or cyano-rich scaffolds can stabilize acceptor orbitals and strengthen charge-transfer character. Amino-functionalized bipyridine in Ag₁₂bpy-NH₂ enhances intersystem crossing and creates dual emission, while tetraphenylethene-derived linkers in TUS 1 and TUS 2 introduce aggregation-restricted luminescence that remains active in water. Sulfonyldiimidazole in TUS 8 produces ultraviolet emission in aqueous media and allows antibiotics to generate analyte-specific spectral shifts. Tetrazine in TUS 9 creates a nitrogen-rich, electron-deficient recognition field that couples amino-acid binding to luminescence attenuation.

Guest molecules provide another tuning axis. In Ag₁₀bpy-CH₃CN, coordinated acetonitrile functions as an optical switch: removal of CH₃CN distorts the Ag₁₀S₆ core and suppresses emission, while recoordination restores luminescence. In flexible Ag₁₀bpy, chloromethanes produce different emission colors because each guest imposes a different orientation, dipole arrangement, and pore-expansion state. In mesoporous Ag₁₂–TPPE frameworks, guest dye encapsulation creates dual-emissive host–guest phosphors, enabling white-light generation by balancing framework and guest emission. These examples reveal a general principle: pores in Ag NCMOFs are not empty space; they are programmable optical microreactors where guests can reshape excited-state decay.

Temperature can also reveal hidden emissive channels. Several Ag NCMOFs show enhanced low-temperature emission because cooling suppresses vibrational relaxation and strengthens radiative decay. Ag₁₈bpy-NH₂ develops a low-energy phosphorescent band at cryogenic temperature, producing ratiometric thermometric behavior. Chiral Ag₂₀ frameworks show temperature-dependent multicolor circularly polarized luminescence, where low-temperature rigidification activates long-lived phosphorescent states. In these cases, the framework functions as a cryogenic amplifier of otherwise weak triplet pathways.

Mechanical force introduces still another form of emission control. Grinding can alter intercluster packing, weaken noncovalent contacts, change Ag···Ag distances, and modify charge-transfer pathways. Solvent fuming can reverse these changes by restoring crystallinity or reorganizing packing. This makes some Ag NCMOFs mechanoluminescent or mechanochromic materials in which optical color becomes a reporter of lattice stress. Such behavior is particularly valuable because it demonstrates that photophysics is not encoded only in molecular structure, but also in the mesoscale arrangement of crystalline domains.

3.4. Emergent Photophysics after Reticularization

Reticularization does more than preserve the luminescence of isolated Ag NCs; it creates photophysical behavior that does not exist in the molecular cluster or free linker alone. This emergent behavior arises from the coexistence of atomic precision and periodic order. The cluster supplies quantized metal-based states, the linker supplies tunable organic orbitals, and the framework imposes distance, orientation, rigidity, and porosity. The resulting material behaves as a collective optical lattice rather than a simple assembly of independent emitters.

The first emergent property is enhanced stability-coupled emission. Many isolated Ag NCs are too fragile to serve as reliable emitters, especially under air, light, moisture, or solvent exposure. Reticularization suppresses decomposition by distributing structural stress through the framework and replacing labile surface ligands with directional linkers. As a result, weak molecular emitters become durable solid-state luminophores. This transformation is central to the identity of Ag NCMOFs: their optical function is inseparable from their framework stabilization.

The second emergent property is dual or multimodal emission. By combining cluster-centered triplet states with linker-centered singlet states, Ag NCMOFs can exhibit fluorescence–phosphorescence duality, ratiometric readout, afterglow, CPL switching, thermochromism, or guest-modulated color shifts. These behaviors require precise spatial coupling between cluster and linker, which is difficult to achieve in physical mixtures. Reticular frameworks impose this coupling crystallographically, making the excited-state architecture reproducible and structurally interpretable.

The third emergent property is analyte-responsive excited-state engineering. In conventional molecular sensors, analyte binding usually changes intensity through quenching or enhancement. In Ag NCMOFs, analytes can also alter coordination environments, pore polarity, Ag···Ag distances, hydrogen-bond networks, lattice dimensionality, and charge-transfer pathways. This is why oxygen sensing, chloromethane discrimination, Fe³⁺ detection, antibiotic recognition, amino-acid sensing, and water-vapor detection each operate through distinct photophysical mechanisms. The same material class can support triplet quenching, static quenching, dynamic quenching, charge-transfer suppression, guest-induced emission shifts, surface-enhanced Raman scattering (SERS) activation, and structural phase transformation.

The fourth emergent property is framework-level optical memory. In materials such as Ag₁₀bpy-CH₃CN or Ag₁₂-TCNB, the optical state depends on whether a guest is coordinated, removed, or reintroduced. , These transformations can be reversible, allowing the framework to cycle between emissive states. The optical output therefore records a structural event: coordination, dehydration, hydration, pore opening, or lattice rearrangement. This is a powerful conceptual shift. Ag NCMOFs are not only luminescent solids; they are crystalline media in which molecular events can be written into the lattice and read out optically. Overall, the photophysics of reticularized Ag NCs is best understood as a hierarchy. At the smallest scale, Ag nuclearity and ligand coordination define molecular orbitals. At the intermediate scale, linkers regulate charge transfer, rigidity, and spin–orbit-assisted excited-state evolution. At the framework scale, topology, dimensionality, porosity, and dynamics determine how excitations migrate, decay, or respond to guests. These interconnected structure–photophysics relationships and their evolution from cluster-level excited states to programmable framework-level optical behavior are summarized schematically in Scheme . This multiscale coupling is the defining photophysical signature of Ag NCMOFs. It explains why reticularization transforms Ag NCs from fragile molecular emitters into programmable optical materials and why future progress will depend on designing not only brighter clusters, but more intelligent cluster lattices.

1. Conceptual Flowchart Summarizing the Multiscale Photophysics of Reticularized Ag NCs .

^a Reticularization integrates cluster-derived electronic states, linker electronics, framework rigidification, intercluster communication, and guest-accessible pore environments to regulate excited-state processes and structure–luminescence relationships, ultimately giving rise to stabilized, multimodal, and stimulus-responsive photophysical behavior.

4. Reticularized Silver Nanoclusters for Sensing

The evolution of reticularized Ag NCs into sensing materials is not merely a story of brighter emission; it is a story of converting structural precision into chemical perception. In these materials, the Ag cluster is no longer an isolated luminophore vulnerable to oxygen, moisture, or ligand dissociation. Instead, it becomes an electronically addressable node embedded within a crystalline communication network, where guest binding, framework motion, charge-transfer perturbation, and local polarity changes are translated into optical or Raman-readable outputs. The most compelling feature of this family is therefore not only sensitivity, but the unusual ability to connect a sensing response to an atomically resolved structural event. Early work on Ag₁₂-based NCMOFs established this principle with exceptional clarity. The Ag₁₂bpy framework transformed an unstable, weakly emissive silver chalcogenolate cluster into a chemically robust porous luminophore with a room-temperature quantum yield of 12.1% and stability extending beyond one year. More importantly, the framework behaved as a dual-function optical switch: oxygen rapidly extinguished the emission, whereas volatile organic molecules restored or modulated the luminescence. The oxygen response was ultrafast, occurring in less than 1 s, with 93.6% quenching at 21 kPa O₂, 98.4% quenching at 100 kPa O₂, a Stern–Volmer constant (K _SV) of 0.639 kPa^–1, and a detection limit (LOD) of 32 Pa. This remarkable performance arises from the combination of accessible channels and moderately long-lived cluster-centered excited states, which permit rapid oxygen diffusion and efficient excited-state deactivation while maintaining structurally uniform sensing sites throughout the crystal. Retention of single crystallinity during guest uptake allowed the sensing process to be interrogated crystallographically, revealing the preferred locations of molecular guests within the framework and making this system a rare example in which gas sensing can be understood simultaneously through optical response and atomic-level structural analysis. Ligand engineering subsequently transformed Ag₁₂ frameworks from simple intensity-dependent oxygen probes into ratiometric sensing platforms (Figure a). In Ag₁₂bpy-NH₂, amino substitution on the bipyridyl linker introduced dual fluorescence–phosphorescence emission from the same chromophoric environment. The blue fluorescence at ca. 456 nm served as an internal reference, whereas the yellow phosphorescence at ca. 556 nm acted as the oxygen-responsive channel (Figure b). The lifetime contrast between the two emissions was enormous, differing by about 8.5 × 10⁶ times, while the spectral separation of approximately 100 nm enabled readily visible color changes. This material detected trace oxygen under hypoxic conditions with a detection limit as low as 0.1 ppm and a response time of 0.3 s (Figure c). The significance of this work lies in the fact that the linker did not simply decorate the framework; it fundamentally reshaped excited-state dynamics. By strengthening spin–orbit coupling and promoting intersystem crossing, the amino substituent

6.

(a) Oxygen-dependent evolution of emission color in the dual-emissive Ag₁₂bpy-NH₂ framework. (b) Reversible fluorescence–phosphorescence switching during alternating oxygen/vacuum cycles. (c) Rapid phosphorescence response of Ag₁₂bpy-NH₂ upon oxygen exposure. Adapted with permission from ref . Copyright 2020, The Author(s). (d) Chloromethane-induced luminescence responses of flexible Ag₁₀bpy under UV irradiation. (e) Guest-dependent emission profiles of Ag₁₀bpy following incorporation of CH₂Cl₂, CCl₄, and CHCl₃. (f) Temperature-dependent emission behavior of guest-free Ag₁₀bpy and CHCl₃-loaded Ag₁₀bpy, illustrating the influence of confined guest dynamics on the photophysical output. Adapted with permission from ref . Copyright 2018 American Chemical Society.

amplified triplet-state population and extended phosphorescence into the millisecond regime, thereby enabling a self-referencing oxygen sensor within a single crystalline architecture.

Several Ag cluster frameworks reveal that vapor sensing can also proceed through structural transformation rather than simple adsorption. In Ag₁₀bpy/Ag₁₀bpy-CH₃CN, coordinated acetonitrile controls an erasable photoluminescent switch. Removal of CH₃CN converts brightly emissive Ag₁₀bpy-CH₃CN into quenched Ag₁₀bpy through subtle distortion of the Ag₁₀S₆ core, whereas exposure to acetonitrile vapor restores green emission within seconds. The switching remains repeatable over 20 cycles and is highly selective against many common solvents. This is a particularly elegant sensing mode because CH₃CN is not detected through nonspecific polarity effects; it is recognized by its ability to re-coordinate, reshape the Ag···Ag/Ag–S environment, and restore the emissive charge-transfer pathway. A more multifaceted stimulus response emerged in Ag₁₈bpy-NH₂, a 1D silver-cluster chain constructed by linking Ag₁₈S₁₀ nodes with amino-functionalized bipyridyl linkers. Unlike systems designed for a single sensing modality, this framework responded reversibly to both mechanical and thermal perturbations. Mechanical grinding transformed the emission from blue to cyan, while exposure to ethanol/acetone vapor restored the original luminescence. The material also displayed pronounced thermochromic behavior between 303 and 83 K. Upon cooling, an additional low-energy emission centered near 548 nm gradually developed and exhibited a long-lived decay of 32 ms, characteristic of triplet-state phosphorescence. The coexistence of high- and low-energy emissive channels generated a temperature-dependent intensity ratio that remained linear across a broad 83–303 K interval, enabling self-referenced optical thermometry. Although not a conventional chemical sensor, this study broadened the functional landscape of Ag NCMOFs by demonstrating how external mechanical and thermal stimuli can be translated into reversible spectral and lifetime signatures. Flexible Ag₁₀bpy provides an elegant example of how dynamic pore architectures can discriminate between structurally similar guest molecules. Upon exposure to chloromethanes, the framework generated readily distinguishable luminescence signatures: CH₂Cl₂ preserved the original green emission, CCl₄ induced only a modest bathochromic shift, whereas CHCl₃ produced a substantially larger red shift of approximately 52 nm (Figure d,e). The emission efficiency was likewise highly dependent on the incorporated guest, with CHCl₃ causing a pronounced enhancement relative to the evacuated framework. Detailed crystallographic and spectroscopic investigations revealed that these contrasting responses do not simply follow solvent polarity or dielectric trends. Instead, they originate from the interplay of framework breathing, guest-induced pore expansion, and the specific orientation of confined chloromethane molecules relative to the emissive bipyridyl chromophores. Variable-temperature studies further uncovered an unusual segmented emission behavior associated with the progressive liberation of CHCl₃ mobility within the channels, linking host–guest dynamics directly to the optical output (Figure f). This work demonstrates that Ag NCMOFs can amplify subtle differences in molecular geometry and dipolar organization into clearly distinguishable photoluminescent fingerprints.

Transitioning from gas-phase recognition to explosive-related analytes, the bpy-directed 3D Ag NCMOF generated through cluster rearrangement serves as an efficient luminescent platform for detecting nitroaromatic compounds, particularly 2-nitrotoluene and 2,4-dinitrotoluene. The material combines an interwoven 3D framework, persistent green photoluminescence under ambient conditions, high resistance to photodegradation, and excellent regeneration capability, all of which are advantageous for practical sensing. Upon exposure to nitroaromatic vapors, the emission intensity decreases markedly, whereas most common organic vapors produce only minimal perturbation. This selective response originates from electronic communication between the excited Ag cluster–linker network and the low-lying acceptor states of the nitroaromatic guests, which efficiently promote non-radiative deactivation. More broadly, this study illustrates how linker-directed structural evolution can redefine functionality: pyrazine organizes the clusters into a layered 2D architecture, while bipyridine drives the formation of a rigid interpenetrated 3D network whose enhanced stability, photostability, and accessible void space collectively enable selective detection of explosive surrogates. The sensing capabilities expanded further with the emergence of water-stable Ag NCMOFs. TUS 1 and TUS 2 are 3D networks assembled from Ag₁₂ cluster vertices and tetraphenylethene-derived tetrakis­(pyridyl) linkers bearing either ethynyl or vinyl spacers (Figure e,f). Unlike many earlier cluster-based frameworks whose structures are readily perturbed by solvent environments, both materials preserve their crystallinity and emissive behavior across media with markedly different polarities, enabling luminescence-based operation in water. Their aqueous dispersions exhibit pronounced fluorescence responses toward Fe³⁺, producing detection limits of 0.05 nM for TUS 1 (Figure a) and 0.86 nM for TUS 2 while maintaining excellent discrimination against competing metal ions (Figure b,c). The superior sensitivity of TUS 1 originates from the distinct electronic communication established by the more conjugated linker architecture, which modifies the excited-state characteristics of the Ag cluster–organic framework and amplifies the quenching response toward Fe³⁺. Beyond the analytical performance itself, this work demonstrates how deliberate manipulation of linker conjugation can regulate photophysical behavior in silver cluster frameworks, opening opportunities for environmentally relevant ion sensing under aqueous conditions.

7.

(a) Progressive quenching of the photoluminescence of TUS 1 upon increasing Fe³⁺ concentration in water. (b) Comparative emission responses of TUS 1 toward representative metal ions. (c) Competitive sensing experiments demonstrating the selective recognition of Fe³⁺ in multicomponent ionic environments. Adapted with permission from ref . Copyright 2023 The Royal Society of Chemistry. (d) Relative luminescence responses of TUS 8 toward various antibiotics. (e, f) Concentration-dependent emission modulation of TUS 8 induced by furazolidone and ornidazole, respectively. Adapted with permission from ref . Copyright 2025 The Royal Society of Chemistry. (g) Proposed SERS-based Hg²⁺ detection pathway involving thiolate displacement, exposure of Ag sites, and subsequent Ag–Hg amalgamation within the cluster node. Reprinted with permission from ref . Copyright 2024, American Chemical Society. (h) Preparation of TUS 9 and its ladder-like Ag₁₃-cluster architecture, illustrating preferential interactions with basic amino acids mediated by tetrazine-containing recognition sites. Reprinted with permission from ref . Copyright 2026 The Royal Society of Chemistry.

TUS 4 takes the platform beyond luminescence into SERS. This 3D Ag₁₂ framework, built with a tetradentate spirobifluorene linker (Figure b), serves as a crystalline SERS probe for Hg²⁺. After NaBH₄ treatment, Hg²⁺ triggers Ag–Hg amalgam formation (Figure g) and generates intense Raman enhancement, giving a linear response from 0.1 to 1 pg mL^–1 and an ultralow detection limit of 0.07 pg mL^–1. The selectivity persists against Mg²⁺, Fe³⁺, Ni²⁺, Cu²⁺, Cd²⁺, Cu⁺, and Au⁺ and is applicable to tap water, river water, and seawater. The key structure–function message is striking: the intact crystalline framework is essential. Grinding weakens the architecture-dependent optical/Raman behavior, showing that SERS activity is not merely a property of silver content, but of atomically organized Ag nodes positioned within a stable 3D scaffold.

TUS 8 illustrates how reticularized Ag₁₂ clusters can detect antibiotics in water with analyte-specific spectral codes. Constructed from Ag₁₂ cluster vertices and sulfonyldiimidazole bridges, this 2D framework exhibits intense ultraviolet-excited emission in water, reflecting the strong electronic coupling established within the cluster–linker network. Upon exposure to antibiotic molecules, the luminescence response depends strongly on analyte identity, generating distinct spectral fingerprints rather than a uniform quenching behavior (Figure d). Furazolidone and nitrofurazone produce the most pronounced attenuation of emission, displaying K _SV of 2414.4 and 2071.7 M^–1 and detection thresholds of 311 and 363 μM, respectively (Figure e). In contrast, ornidazole and dimetridazole induce more moderate intensity changes accompanied by opposite wavelength shifts (Figure f), while chloramphenicol elicits only a relatively weak response. These contrasting optical signatures originate from different modes of guest–framework interaction. The strongly electron-deficient nitrofuran derivatives perturb the electronic distribution within the emissive framework, leading to a higher-energy emission profile, whereas nitroimidazole antibiotics establish favorable heteroaromatic interactions with the imidazole-containing linker environment, promoting greater excited-state delocalization and a lower-energy emission response. Importantly, the framework retains both its crystallinity and sensing performance through repeated use, highlighting the robustness of the Ag₁₂-based architecture. This work illustrates how deliberate cluster–linker engineering can transform silver nanocluster frameworks into luminescent platforms capable of distinguishing structurally related contaminants through analyte-dependent spectral outputs rather than intensity changes alone. TUS 9 pushes molecular recognition further by using a tetrazine-lined ladder architecture to discriminate amino acids. The material is built from Ag₁₃ cluster chains laterally connected by 3,6-di­(4-pyridyl)-1,2,4,5-tetrazine linkers. In water, it emits at 377 nm and is selectively quenched by basic amino acids. l-Lysine gives K _SV = 891.7 M^–1 and LOD = 407 μM, while l-arginine gives K _SV = 540.1 M^–1 and LOD = 162 μM. Acidic amino acids such as aspartic acid and glutamic acid show much weaker quenching, with K _SV values of only 53.5 and 77.5 M^–1 (Figure h). This marked difference originates from the electrostatic landscape created by the tetrazine-rich linker environment. Cationic side chains can establish favorable noncovalent contacts with the nitrogen-rich tetrazine motifs, positioning the guest molecules close to the emissive cluster–linker domain and facilitating excited-state deactivation. By comparison, amino acids bearing negatively charged carboxylate groups exhibit much weaker affinity for the framework and therefore perturb the photophysical behavior only marginally. As a result, TUS 9 effectively translates differences in amino-acid charge and functionality into distinct optical responses. The sensing process remains fully reversible, with the framework retaining its performance through ten consecutive sensing–regeneration cycles, while post-analysis XPS measurements reveal no detectable alteration of the silver coordination environment. A distinct sensing strategy emerges in the Ag₁₂-TCNB family, where moisture detection is achieved through framework reconfiguration rather than conventional fluorescence quenching. The Ag₁₂-TCNB architecture incorporates electron-accepting 1,2,4,5-tetracyanobenzene linkers (Figure a) that connect Ag₁₂ cluster nodes into an extended 3D network. Exposure to trace amounts of water produces an immediate and easily observable luminescence shift from orange to yellow, allowing direct visual identification of moisture at extremely low relative humidity. Structural investigations using single-crystal and powder X-ray diffraction revealed that water molecules actively participate in the coordination environment of the framework. By competing with selected Ag–N interactions and establishing new hydrogen-bonding motifs, water promotes a reversible transformation from the original 3D architecture to a hydrated layered phase (Figure ). As a result, the photoluminescence response originates from a modification of the cluster electronic environment induced by framework rearrangement rather than from simple guest adsorption. The hydrated state exhibits emission characteristics nearly identical to those of the isolated water-containing phase, providing compelling evidence that moisture exposure generates a distinct structural and photophysical state. This behavior highlights an unconventional sensing paradigm in which framework flexibility becomes a functional advantage. Instead of merely accommodating guest molecules, the reticular architecture translates subtle hydration events into large optical changes through cooperative structural and electronic reorganization. Together with previous examples involving gases, volatile organic compounds, metal ions, amino acids, and antibiotics, this study demonstrates that reticularized Ag NCs function as integrated sensing platforms where optical output is governed by the interplay of cluster-centered emissive states, linker-controlled recognition, analyte transport pathways, and dynamic framework adaptation. Gas and vapor detection primarily exploits diffusion-driven excited-state perturbation, ionic analytes engage charge-transfer and metal–metal interactions, biomolecular recognition arises from tailored host–guest contacts, whereas moisture sensing uniquely relies on reversible lattice reconstruction. These advances suggest that future developments in Ag NCMOFs will increasingly focus on establishing direct structure–response relationships, enabling sensing mechanisms that can be rationalized and predicted from atomic-level structural changes.

8.

H₂O-responsive framework reorganization in Ag₁₂-TCNB. (Left) Water-triggered transformation of the Ag₁₂-TCNB 3D-3D architecture into the Ag₁₂-TCNB 2D-H₂O layered phase through modulation of Ag­(I) coordination environments. (Right) Reconfiguration of intermolecular hydrogen-bonding interactions accompanying hydration, illustrating the emergence of H₂O-mediated connections between neighboring Ag₁₂ cluster nodes. Reprinted with permission from ref . Copyright 2026 Wiley-VCH GmbH.

5. Beyond Sensing: Emerging Functional Directions

5.1. Optoelectronic and Photonic Materials

Extending Ag NCMOFs from conventional luminescent solids into adaptive chiroptical media, Zang and co-workers developed a pair of enantiomeric Ag NC assemblies by first encoding molecular chirality into atomically precise R/S-Ag₂₀ NCs and then reticulating them with N-donor bridging linkers. The parent clusters, formulated as (CO₃)@Ag₂₀( ^t BuS)₁₀(R/S-THF-COO)₈(DMF)₄, possess a drum-like Ag₂₀S₁₀ skeleton composed of two Ag₅S₅ pentagrams and an equatorial Ag₁₀ ring, in which chiral tetrahydrofuran carboxylate ligands distort the silver–sulfur core and transmit chirality from the organic periphery into the metallic cluster. Replacement of labile DMF ligands with 3-amino-4,4′-bipyridine produced crystalline R/S-Ag₂₀bpy-NH₂ frameworks, in which the Ag₂₀ clusters are assembled into a chiral 2D sql net while preserving the cluster core and propagating chirality across the extended framework through C–H···O and N–H···O interactions. Unlike a static circularly polarized luminescence (CPL) emitter, this Ag NCMOF behaves as a temperature-readable chiral photonic material: at room temperature it displays blue emission around 480 nm and mirror-image circularly polarized luminescence with |g _lum| values of ca. 1 × 10^–3, whereas cooling to 83 K activates additional long-lived low-energy phosphorescent bands at 571 and 680 nm, giving a visually distinct blue-to-pink emission transition. This thermally triggered dual-emission response enables ratiometric luminescence thermometry over broad temperature windows, with the low-energy cluster-centered/charge-transfer emissions becoming increasingly dominant at low temperature owing to framework rigidification and suppression of nonradiative decay. Most strikingly, the CPL output itself becomes dynamically switchable: a single blue CPL band at room temperature transforms into spatially separated multicolor CPL signals at low temperature, spanning much of the visible region. The central advance of this study is therefore not simply the construction of a chiral Ag NCMOF, but the conversion of atomically precise Ag NCs into an intelligent solid-state chiroptical platform in which chirality transfer, framework assembly, temperature-dependent charge-transfer emission, afterglow, and CPL switching are integrated within one crystallographically defined material.

A significant advance toward device-integrated optoelectronics based on reticularized Ag NCs was reported by Li, Zang, and co-workers, who constructed a mesoporous silver–chalcogenolate NCMOF, 1 ⊃ DMAC, by reticulating cuboctahedral Ag₁₂(S ^t Bu)₆(CF₃COO)₆ cluster nodes with the aggregation-induced-emission (AIE)-active tetraphenylethene-type linker TPPE. The resulting non-interpenetrated 3D framework crystallized as a highly symmetric she-type network, in which each Ag₁₂ cluster behaves as a six-connected node and TPPE as a four-connected linker, generating an unusually open crystalline scaffold with 74.2% free volume and cubic mesoporous cages as large as 32 Å. This large-pore architecture was not merely a structural curiosity; it functioned as a molecular photonic chamber in which guest molecules could be inserted to rewrite the emission output of the Ag NCMOF. The pristine DMAC-filled framework emitted intense blue light at ca. 454 nm with a high photoluminescence quantum yield of 49.9%, whereas removal of DMAC shifted the emission to green at ca. 530 nm, demonstrating guest-modulated emission from the TPPE-centered AIE process. Most importantly for optoelectronic translation, encapsulation of the yellow–red emissive dye DPP into the mesopores created a dual-emissive host–guest phosphor, 1 ⊃ DPP, in which the blue emission of the framework and the longer-wavelength DPP emission could be balanced by controlling guest loading. At an optimized DPP concentration of 0.5 mmol L^–1, the material delivered near-white emission with CIE coordinates of (0.32, 0.32). A simple white-light-emitting diode (LED) was then fabricated by directly coating 1 ⊃ DPP-0.5 onto a commercial 365 nm UV LED chip; upon operation at 4.5 V, the device produced bright white light, validating the Ag NCMOF as a processable crystalline phosphor for solid-state lighting. The key advance of this study lies in showing that mesoporosity and reticular precision can be used together to transform an Ag NCMOF from a static luminescent solid into a guest-programmable optical platform, where the framework supplies crystallinity, stability, blue AIE emission, and spatial confinement, while the pore-confined guest supplies complementary emission for white-light generation.

Mandal and co-workers recently pushed Ag NCMOFs into the territory of molecular nanoelectronics by transforming a discrete cuboctahedral Ag₁₂ NC, Ag₁₂(SAdm)₆(CF₃COO)₆(pyridine)₆, into a 1D cluster-assembled material through 4,4′-bipyridine bridges while preserving the Ag₁₂ core integrity. This structural conversion is not merely a dimensional upgrade, but an electronic reprogramming event: the isolated Ag₁₂ units, originally separated as molecular islands, become wired into an extended −Ag–bpy–Ag– pathway that enables more efficient charge migration across the cluster chain. To probe this effect, sandwich-type resistive memory devices were fabricated by spin-coating either the molecular Ag₁₂ NC or the 1D Ag₁₂ NCMOF onto ITO glass, followed by Ag top-electrode deposition, giving ITO/Ag₁₂ NC/Ag (Figure a) and ITO/Ag₁₂ NCMOF/Ag architectures (Figure b). The 1D Ag₁₂ NCMOF device displayed markedly superior resistive switching, with stable high- and low-resistance states, endurance over 1000 cycles, an average ON/OFF ratio of ∼70, and retention behavior consistent with nonvolatile memory operation (Figure f–h), whereas the discrete Ag₁₂ NC device showed a much lower ON/OFF ratio of ∼13 (Figure c–e). Most intriguingly, the cluster-chain device also exhibited negative differential resistance, with a peak-to-valley ratio of 2.34 and a switching efficiency of 23 nS, suggesting potential for multilevel memory and advanced neuromorphic or logic-type functions. The enhanced performance was attributed to the ordered cluster-to-cluster connectivity, shorter Ag···Ag contacts, trap-filled space-charge-limited conduction, and intercluster charge-transfer states revealed by Time-dependent density-functional theory (TD-DFT). Thus, this study identifies reticularization as a powerful strategy for converting atomically precise Ag NCs from photophysical building blocks into addressable electronic media, where the framework acts as both a structural scaffold and a programmable charge-transport highway.

9.

(a, b) Device architectures employing discrete Ag₁₂ NCs and 1D Ag₁₂ NCMOF on ITO substrates. (c–h) Representative resistive switching characteristics, including initial current–voltage responses, cycle-dependent hysteresis, retention behavior, and proposed switching states, demonstrating enhanced memory performance after cluster assembly. Adapted with permission from ref . Copyright 2024 Wiley-VCH GmbH. (i) Configuration of a bottom-gated field-effect transistor incorporating a monolayer Ag₁₂-azo-bpy semiconductor. (j) AFM image of the device channel. (k, l) Output and transfer characteristics revealing p-type charge transport. Adapted with permission from ref . Copyright 2023 American Chemical Society. (m) Depiction of UV-induced structural evolution associated with TFA release and vacancy generation in Ag NCMOF crystals. (n) Comparison of single-crystal electrical transport before and after photoinduced transformation. (o, p) Temperature-dependent conductivity measurements and Arrhenius analysis illustrating thermally activated charge transport. Adapted with permission from ref . Copyright 2025 The Author(s).

In a separate study, Mandal and co-workers demonstrated that reticularized Ag NCs can function as intrinsically semiconducting building blocks for transistor technologies by constructing a 2D Ag NCMOF, Ag₁₂-azo-bpy, from cuboctahedral Ag₁₂(S ^t Bu)₆(CF3COO)₆ cluster nodes interconnected through 4,4′-azopyridine linkers. Structurally, the material adopts a honeycomb-like layered architecture in which each Ag₁₂ node is electronically stitched into an extended in-plane network, while adjacent layers interact only through weak van der Waals contacts. This anisotropic connectivity proved crucial: liquid-phase exfoliation generated atomically thin sheets (ca. 0.76–0.78 nm) that effectively isolated the electronically active cluster–linker plane and unlocked transport characteristics inaccessible in the bulk material. Conductive atomic force microscopy (AFM) measurements (Figure j) revealed that charge transport is largely confined within individual layers, whereas interlayer conduction rapidly diminishes with increasing thickness, highlighting the importance of dimensional reduction for carrier mobility. Electronic-structure calculations provided an unusually clear structure–property relationship, showing that the valence-band edge is predominantly localized on the Ag₁₂ cluster nodes, while the conduction-band minimum resides on the azo-containing linker framework. This spatially segregated band architecture favors hole generation and transport through the interconnected silver-cluster lattice, effectively transforming the cluster nodes into metallic relay stations embedded within a conjugated molecular circuit. Exploiting this electronic configuration, bottom-gated field-effect transistors (FETs) (Figure i) fabricated from monolayer Ag₁₂-azo-bpy exhibited intrinsic p-type semiconducting behavior, achieving a hole mobility of 1.215 cm² V^–1 s^–1, a carrier density of 4.98 × 10¹⁸ cm^–3, and an ON/OFF current ratio approaching 4.5 × 10³ under ambient conditions, together with operational stability over extended periods (Figure k,l). These figures compare favorably with many solution-processed molecular and nanocluster semiconductors and represent one of the most compelling demonstrations of charge transport in an atomically precise Ag-cluster framework. More fundamentally, this work establishes a new design principle for Ag NCMOF electronics: rather than treating nanoclusters as isolated quantum objects, reticularization can organize them into electronically coherent 2D lattices where cluster nodes define the transport channels, organic linkers mediate directional coupling, and crystallographic precision translates directly into transistor-level functionality.

Pushing the concept of electronic structure engineering beyond linker selection and dimensional control, Zhang and co-workers introduced a fundamentally different strategy in which charge transport was regulated through crystallographically resolved vacancy creation within an Ag NCMOF. Starting from a highly ordered Ag₁₂–TCNB assembly constructed from cuboctahedral [Ag₁₂( ⁱ PrS)₆] cluster nodes and tetracyanobenzene (TCNB) linkers, the authors discovered that controlled UV irradiation could trigger a single-crystal-to-single-crystal transformation accompanied by the selective removal of weakly coordinated trifluoroacetic acid species and partial loss of para-coordinated TCNB linkers (Figure m). Rather than generating random defects, this process produced ordered vacancy sites with precisely defined occupancies, converting an initially 2D–3D interpenetrated architecture into a vacancy-containing 3D–3D framework while preserving long-range crystallinity. The significance of these vacancies extends far beyond structural modification. At the atomic scale, removal of coordinating species shortens electronic communication pathways between neighboring Ag₁₂ building units, promotes stronger intermolecular π-stacking and C–H···π interactions, and creates additional defect-derived electronic states that facilitate carrier migration throughout the framework. As vacancy concentration increases, the optical band gap collapses dramatically from 1.92 to 0.57 eV, the absorption profile broadens across the visible region, and electron paramagnetic resonance together with positron-annihilation measurements reveal a substantial increase in defect density and charge-delocalization capability. Most remarkably, the conductivity of individual single crystals increased by nearly fifty-fold to 1.45 × 10^–6 S cm^–1 after irradiation (Figure n), while preserving semiconducting characteristics, as evidenced by thermally activated Arrhenius-type charge transport with an activation energy of approximately 0.30 eV (Figure o,p). In contrast, the vacancy-free regrown analogue exhibits conductivity comparable to the parent material, unequivocally establishing vacancies as the dominant origin of enhanced charge transport. This work therefore introduces a powerful paradigm for Ag NCMOF electronics: conductivity need not arise solely from increasing framework conjugation or cluster connectivity; it can instead be programmed through atomically defined vacancy landscapes that reshape band structures, generate charge-carrying defect states, and strengthen intercluster electronic coupling while retaining single-crystal order. In doing so, the study elevates vacancy engineering from a defect phenomenon to a deliberate design principle for next-generation cluster-based optoelectronic materials.

5.2. Programmable Catalytic Platforms

Ag NCMOFs offer an unusually powerful platform for catalytic detoxification of sulfur mustard because they merge three functions that are difficult to integrate in conventional molecular photosensitizers: a porous crystalline scaffold for rapid uptake of volatile sulfides, Ag-rich cluster nodes that provide strong host–guest affinity toward chloroalkyl sulfide substrates, and photoactive organic linkers that convert molecular oxygen into singlet oxygen for selective oxidation. Zang and co-workers first demonstrated this concept using a porphyrinic Ag NCMOF, Ag₁₂TPyP, formulated as [Ag₁₂(S ^t Bu)₆(CF₃COO)₃(TPyP)] _n , in which cuboctahedral Ag₁₂ chalcogenolate nodes are reticulated by tetra­(4-pyridyl)­porphyrin linkers (Figure c) into a robust 2D framework. In this architecture, the Ag₁₂ nodes are not passive structural joints: they enrich 2-chloroethyl ethyl sulfide (CEES) through Ag···Cl interactions, while the porphyrinic linkers harvest visible light and cooperate with the silver clusters to accelerate ¹O₂ generation. As a result, Ag₁₂TPyP combined capture and photocatalysis in one crystalline solid, showing CEES uptake of 74.2 mg g^–1 and extremely rapid visible-light oxidation of CEES to the less toxic sulfoxide CEESO, reaching 98% conversion within 4 min under O₂ with a half-life of only 1.5 min and 100% selectivity without detectable overoxidation to toxic sulfone. Even under air, complete conversion was achieved within 14 min, and the catalyst retained full activity over four consecutive cycles while preserving crystallinity, highlighting the practical value of framework stabilization for recyclable decontamination. Building on this capture–photosensitization logic, the later BODIPY-based silver chalcogenide cluster MOF study moved closer to realistic defense scenarios by shifting from liquid-phase CEES degradation to real-time detoxification of flowing gaseous CEES. Through systematic linker engineering, Zang and co-workers showed that Ag₁₂–BDP-I (Figure a), constructed from Ag₁₂ clusters and iodine-functionalized BODIPY linkers (Figure g), provided the most effective catalytic microenvironment: the porous 2D kgd-type framework supplied accessible channels, CF₃/alkyl-lined pore surfaces suppressed competitive water adsorption, Ag sites promoted CEES binding, and iodine substitution enhanced spin–orbit coupling to facilitate intersystem crossing and boost ¹O₂ production. Under continuous-flow gas–solid conditions, Ag₁₂–BDP-I captured and converted gaseous CEES almost immediately at a flow rate of 20 mL min^–1 across a wide humidity range of 10–90% RH, maintaining near-complete adsorption and conversion while avoiding formation of toxic CEESO₂ (Figure b). Control experiments with nonporous Ag₁₂–BDP, less porous Ag₁₂–BDP-Py, iodine-free Ag₁₂–BDP-H, isolated Ag₁₂ clusters, and free BDP-I revealed the key structure–function hierarchy: Ag₁₂ clusters dominate substrate capture, BODIPY units drive photooxidation, iodine accelerates triplet-state formation, and the reticular framework integrates these otherwise separate roles into a single operational catalyst. These studies establish Ag NCMOFs as more than luminescent cluster solids; they function as chemically programmable detoxification reactors in which pore chemistry, heavy-atom photophysics, cluster–substrate affinity, and crystallographic robustness are orchestrated to convert a dangerous sulfide vapor into a benign sulfoxide with speed, selectivity, and recyclability.

10.

(a) Assembly of a BODIPY-derived linker with Ag₁₂ cluster nodes to generate the Ag₁₂BDP-I framework. (b) Performance of Ag₁₂BDP-I toward capture and visible-light-mediated oxidation of gaseous CEES under different humidity conditions. Adapted with permission from ref . Copyright 2023 American Chemical Society. (c) Comparison of CO and H₂ Faradaic efficiencies obtained over Ag₁₂THIT, Ag₁₂TPEB, and Ag₁₂TPMA during acidic CO₂ electroreduction. (d) Projected density of states analysis for the COOH intermediate adsorbed on Ag₁₂THIT. (e) Calculated reaction-energy profiles for CO formation on Ag₁₂THIT, Ag₁₂TPEB, and Ag₁₂TPMA. Adapted with permission from ref . Copyright 2026 Wiley-VCH GmbH. (f) Illustration of ligand fluorination as a strategy for modulating the electronic structure of Ag₁₈ NCMOFs, represented by Ag₁₈BDC and Ag_18FBDC. (g) Plausible catalytic pathway for the Knoevenagel condensation promoted by Ag₁₈FBDC. Reprinted with permission from ref . Copyright 2026 American Chemical Society.

Beyond photooxidative detoxification, Ag NCMOFs have also emerged as highly effective platforms for carbon dioxide valorization, where the atomically precise arrangement of silver atoms provides an opportunity to engineer catalytic sites with a level of structural definition rarely attainable in conventional heterogeneous catalysts. Sun and co-workers illustrated this concept using Ag₂₇-MOF, a robust 2D Ag-cluster framework featuring exposed Ag-rich surfaces that function as readily accessible π-Lewis acidic catalytic sites for alkyne activation. Exploiting this architecture, Ag₂₇-MOF served as an exceptionally efficient heterogeneous catalyst for the carboxylative cyclization of propargylamines with atmospheric CO₂ under remarkably mild conditions. Using only 1 mol % Ag loading, the framework promoted the conversion of a broad range of terminal and internal propargylamines into value-added oxazolidinones in excellent yields, achieving 97% yield for the benchmark substrate within 6 h at room temperature and 1 atm CO₂, while delivering a turnover number as high as 1333. Particularly noteworthy was its ability to transform sterically demanding internal alkynes, a substrate class that often remains challenging for porous catalysts because of restricted accessibility to catalytic sites. Mechanistic studies revealed that this unusual substrate tolerance originates from the open topology of the 2D framework and the exposed Ag-rich saddle surface, which enables effective Ag···π interactions with both terminal and internal CC bonds. Density-functional calculations further showed strong adsorption of alkyne substrates onto the accessible silver centers, accompanied by electron redistribution that activates the carbon–carbon triple bond toward subsequent CO₂ incorporation. Control experiments demonstrated that neither the individual silver precursors nor their physical mixtures could approach the catalytic efficiency of the framework, underscoring that catalytic performance arises from the synergistic integration of cluster topology, exposed metallic surfaces, and reticular organization. More broadly, this study highlights a distinctive advantage of Ag NCMOF catalysis: rather than merely immobilizing catalytic sites within a porous matrix, reticularization transforms atomically precise Ag NCs into cooperative catalytic landscapes where substrate activation, CO₂ capture, and product formation are orchestrated within a single crystalline architecture.

An even more compelling manifestation of catalytic programmability emerges when the electronic landscape of Ag cluster nodes was manipulated for electrocatalytic carbon dioxide conversion (eCO₂RR). Zhao and co-workers demonstrated this strategy through a series of Ag₁₂ NCMOFs for acidic eCO₂RR in which the metallic cluster motif remained unchanged while the surrounding coordination environment was deliberately reconfigured using either imidazole- or pyridyl-based linkers. Among these materials, the imidazole-containing framework Ag₁₂THIT exhibited outstanding catalytic behavior toward CO generation under strongly acidic conditions (pH 2), affording a Faradaic efficiency for CO (FE_CO) of 98.5% at a current density of 328 mA cm^–2 and delivering a CO partial current density of 447.2 mA cm^–2 while maintaining a FE_CO of 96.8% (Figure c). The catalyst sustained catalytic operation for 70 h with only minimal loss of activity, underscoring the robustness imparted by the cluster–framework integration. Unlike conventional catalyst optimization strategies that rely on changing metal composition, this study revealed that the decisive variable was the electronic influence exerted by the linker on the atomically precise Ag₁₂ node. Relative to pyridyl analogues, the more electron-donating imidazole linker generated a more influential coordination environment around the silver cluster, shifting the Ag-derived electronic states toward the Fermi level (Figure d). This electronic reorganization promoted charge redistribution into the key *COOH intermediate, reduced the energetic requirement for its formation, and simultaneously disfavored the competing hydrogen-evolution pathway. Operando infrared spectroscopy identified the emergence of *COOH species during catalysis, while theoretical calculations showed that the energy barrier associated with the rate-determining *COOH-generating step was substantially diminished relative to pyridyl-linked analogues (Figure e). The conceptual importance of this work extends beyond acidic CO₂ reduction itself. It demonstrates that Ag NCMOFs can function as electronically programmable catalytic platforms in which the catalytic behavior of an atomically precise Ag cluster is not fixed by cluster composition alone but can be continuously tuned through reticular control of the surrounding ligand field. Viewed from this perspective, the organic linker acts not merely as a structural connector but as an electronic architect that reshapes the reactivity landscape of the Ag node, enabling framework-level control over intermediate stabilization, reaction energetics, and product selectivity. A complementary illustration of linker-directed catalytic programming was recently uncovered in a family of atomically precise Ag₁₂ NCMOFs spanning pyridine-, pyrazine-, bipyridine-, bis­(pyridyl)­ethane-, and azopyridine-linked architectures for the hydrogen evolution reaction (HER). Remarkably, the metallic Ag₁₂ node remained structurally invariant across the series, yet subtle rewiring of the linker environment produced strikingly different electrocatalytic behaviors, with the pyrazine-linked framework emerging as the most efficient electrocatalyst, requiring an overpotential of only 122 mV to achieve 10 mA cm^–2 while retaining excellent operational stability. Mechanistic investigations further revealed that the linker is not merely a structural spacer but a molecular regulator of catalysis: by modulating linker basicity and intercluster organization, it redirects the preferred hydrogen adsorption site from Ag to S, illustrating that the catalytic personality of an atomically precise Ag NC can be rewritten without changing its atomic composition.

Ligand electronics provide another powerful lever for catalytic programming in Ag NCMOFs. Wang, Geng and colleagues demonstrated this principle using two isostructural 2D Ag₁₈ cluster frameworks, Ag₁₈BDC and

Ag₁₈FBDC, assembled from chromate-templated Ag₁₈ nodes and nonfluorinated or fluorinated dicarboxylate linkers (Figure f). Although both frameworks preserve the same Ag₁₈ catalytic scaffold, fluorination of the linker profoundly changes the electronic personality of the exposed Ag sites. In Knoevenagel condensation between aromatic aldehydes and malononitrile, Ag₁₈FBDC consistently surpassed Ag₁₈BDC, affording 90% yield for benzaldehyde under solvent-free conditions and maintaining superior activity across electron-poor, electron-rich, heteroaromatic, and sterically demanding substrates. The key structure–function message is unusually clear: F substituents withdraw electron density from the Ag₁₈ core, shift the Ag 3d binding energy positively, increase the electropositive character of surface Ag atoms, and strengthen Lewis-acid activation of the aldehyde carbonyl group (Figure g). Thus, the reaction is not merely accelerated by porosity or cluster immobilization; it is electronically tuned at the cluster node itself. This study therefore positions ligand fluorination as a subtle but powerful strategy for converting Ag NCMOFs into electronically adjustable heterogeneous catalysts, where the linker does not simply hold the framework together but actively rewires the catalytic strength of the metal cluster.

A complementary design logic was introduced by Hyeon et al., who used the same cuboctahedral Ag₁₂ core to construct dimensionally distinct 1D, 2D, and 3D cluster-assembled frameworks through N-donor linkers of different geometry. This series is especially valuable because the Ag₁₂ core is preserved across all architectures, allowing catalytic performance to be compared without changing the identity of the metal NC itself. In the NaBH₄-assisted hydrogenation of 4-nitrophenol to 4-aminophenol, all three Ag₁₂ frameworks were catalytically competent, but their activities diverged sharply with dimensionality: the 1D Ag₁₂–Py₂S chain (Figure e) completed the reaction within 11 min with a rate constant of 0.388 min^–1, whereas the 2D Ag₁₂-bpm (Figure c) and 3D Ag₁₂-tmdp (Figure i) frameworks required 60 and 80 min, respectively. This activity order directly follows the accessibility of Ag surfaces, with the lower-dimensional architecture exposing a larger fraction of catalytically usable Ag sites for interfacial electron and hydrogen transfer. The work therefore offers a rare clean demonstration that framework dimensionality can dictate catalysis even when the metal cluster node remains identical. In this sense, Ag NCMOF catalysis becomes a problem of spatial exposure as much as chemical composition: the same Ag₁₂ engine performs differently depending on whether the reticular scaffold cages it, layers it, or arranges it into an open chain.

Das, Negishi, and co-workers further expanded Ag NCMOF catalysis into aqueous redox chemistry by developing TUS 3, a luminescent 2D Ag₁₂ NCMOF constructed from C ₆-symmetric Ag₁₂ nodes and C ₃-symmetric tripodal pyridine linkers (Figure b) into a kgd-type network. The structural merit of TUS 3 lies in its compact yet mesoporous architecture: stacked 2D layers generate uniaxial open channels, provide a BET surface area of 394 m² g^–1, and maintain crystallinity even in water, making the material unusually suitable for solution-phase catalysis. In the reduction of hexacyanoferrate­(III) by NaBH₄, TUS 3 acted as an efficient electron-relay catalyst, accelerating conversion of Fe­(CN)₆ ^3– to Fe­(CN)₆ ^4– in aqueous medium. The catalytic rate increased systematically with catalyst concentration, with the apparent first-order rate constant rising from 55.9 × 10^–2 to 291.9 × 10^–2 min^–1 as TUS 3 concentration increased from 0.1 to 1 nM, and the half-life decreasing to only 14 s at 1 nM. Mechanistically, the framework behaves as a charged conductive interface: NaBH₄ populates the Ag-cluster framework with reducing equivalents, and the mesoporous channels then allow rapid encounter and electron transfer to the ferricyanide acceptor. Importantly, TUS 3 retained catalytic performance over repeated cycles, with FT-IR, PXRD, HRTEM, and EDS confirming preservation of chemical and structural integrity after catalysis. This work highlights how Ag NCMOFs can serve not only as light-driven or Lewis-acid catalysts, but also as robust aqueous-phase redox mediators in which porosity, water stability, and cluster-based electron transfer operate in concert.

An especially elegant demonstration of how reticular architecture can directly govern catalytic function was recently reported by Wang, Zhang and colleagues through a pair of topologically differentiated porphyrinic Ag₁₆ NCMOFs, 2D-Ag₁₆-TPyP and 3D-Ag₁₆-TPyP, that provide an ideal platform for isolating the catalytic consequences of framework connectivity. Because the chemical composition of the node and linker remains essentially unchanged, these materials provide a rare platform in which catalytic behavior can be traced directly to connectivity rather than building-block identity. Remarkably, the two frameworks activate molecular oxygen through fundamentally different pathways under visible-light irradiation. The more open 2D architecture exhibits higher O₂ uptake, lower charge-transfer resistance, stronger photocurrent response, and spatial separation of frontier orbitals between the Ag₁₆ cluster and porphyrin components, thereby promoting electron transfer and efficient generation of superoxide radicals (O₂ ^•–). As a consequence, 2D-Ag₁₆-TPyP functions as a highly effective photocatalyst for aerobic oxidation of aldehydes, achieving quantitative conversion of benzaldehyde to benzoic acid within 1 h and displaying broad substrate tolerance toward both electron-rich and electron-deficient aromatic aldehydes. In contrast, the more compact 3D framework suppresses interfacial electron-transfer pathways while favoring energy transfer, resulting in highly selective production of singlet oxygen (¹O₂). This shift in reactive oxygen species (ROS) generation dramatically alters catalytic output, enabling rapid and quantitative photooxidation of sulfides to sulfoxides, including complete conversion of the high-value precursor iberverin to iberin within only 20 min under ambient conditions, while maintaining excellent chemoselectivity and recyclability. Mechanistic studies combining EPR spectroscopy, photophysical measurements, gas adsorption analysis, and DFT calculations revealed that connectivity regulates catalysis through a dual-control mechanism involving both O₂ adsorption capability and molecular-orbital distribution. More broadly, this work introduces a powerful conceptual advance for Ag NCMOF catalysis: framework connectivity is not merely a structural parameter controlling dimensionality and porosity, but an active design variable capable of steering the fate of photoexcited states, dictating ROS identity, and ultimately programming reaction selectivity from the atomic scale upward.

5.3. Bioactive Interfaces and Molecular Diagnostics

Ag NCMOFs have opened an unusual route to bioprotective materials, where atomically precise Ag NCs are no longer used simply as antimicrobial reservoirs but as organized photoactive units for killing drug-resistant pathogens. Wang, Zang, and co-workers demonstrated this concept with Ag₉–AgTPyP, a 2D silver cluster–porphyrin framework in which Ag₉ nodes are periodically coupled with Ag-metalated porphyrin units. Under visible-light irradiation, the porphyrinic component operates as a light antenna, while the Ag₉ cluster behaves as an oxygen-activating sink that accepts photoexcited electrons and promotes the generation of reactive oxygen species, including ¹O₂, ^•O₂ ^–, and H₂O₂. This cluster–linker charge-transfer pathway is central to the biological performance: Ag₉–AgTPyP eliminated >99.99999% methicillin-resistant Staphylococcus aureus (Figure a,b) and >99.999% Pseudomonas aeruginosa within 2 h, outperforming many conventional photocatalytic antibacterial systems. Beyond suspension tests, the material was processed into films on masks and protective suits, where it showed strong light-triggered killing of aerosolized or liquid-borne superbugs (Figure c,d). The key advance is therefore the conversion of an Ag-cluster framework into a deployable antimicrobial surface, in which visible-light harvesting, oxygen capture, ROS diffusion, hydrophobic anti-adhesion, and Ag-assisted bacterial toxicity are integrated within a single crystalline bioprotective architecture.

11.

(a) Time-dependent photocatalytic elimination of S. aureus mediated by Ag₉–AgTPyP under visible-light irradiation. (b) Comparison of bacterial inactivation efficiencies obtained for Ag₉–AgTPyP, Ag⁺, TPyP, and AgTPP under illuminated and dark conditions. (c) Photograph illustrating evaluation regions on Ag₉–AgTPyP-coated protective fabric and (d) corresponding viable-cell counts after exposure to P. aeruginosa, highlighting the effect of light activation and surface coverage. Undetectable bacterial survival is denoted by “000”. Adapted with permission from ref . Copyright 2021 The Authors. Advanced Science published by Wiley-VCH GmbH. (e) Schematic representation of label-free target DNA recognition enabled by Ag NCMOFs through modulation of the fluorescence background of SYBR Green I-stained probes. (f) Dependence of signal-to-noise ratio (left) and fluorescence response (right) on the concentration of Ag₁₄bpa and Ag₁₂bpeb MOFs in the presence and absence of complementary DNA. Adapted with permission from ref . Copyright 2023 The Royal Society of Chemistry.

A distinct biomedical direction was introduced through a 2D Ag₁₄ NCMOF, [Ag₁₄(S ^t Bu)₁₀(CF₃COO)₄(4,4′-azopyridine)₂], in which Ag₁₄ nodes are stitched by azopyridine linkers into an optically responsive framework. Rather than emphasizing direct therapeutic activity, this study exploited the coupled photon–phonon behavior of the Ag NCMOF for photoacoustic bioimaging. Solvent-mediated structural modulation altered interlayer noncovalent interactions and restricted linker motion, resulting in a remarkable elevation of room-temperature photoluminescence quantum yield, whereby the ethanol/chloroform medium produced an emissive output nearly 650 greater than that obtained in ethanol/acetonitrile. This rigidified excited-state landscape also changed the balance between radiative photon emission and nonradiative phonon generation, enabling photoacoustic signal amplification. Most notably, the authors introduced a pre-illumination strategy that increased the photoacoustic response by >85% in the desired frequency region and demonstrated blood-vessel-mimicking contrast from material embedded inside chicken breast tissue at a depth of ca. 2 mm. The structure–function message is compelling: reticularized Ag clusters can act as atomically precise contrast-generating media, where small changes in cluster–solvent and interlayer interactions reshape excited-state relaxation pathways and translate molecular-level rigidity into macroscopic imaging contrast.

Negishi et al. expanded Ag NCMOF biofunctionality toward label-free molecular diagnostics by developing two acetylenic-linker-based Ag NCMOFs, Ag₁₄bpa and Ag₁₂bpeb, constructed from Ag₁₄ or Ag₁₂ chalcogenolate cluster nodes bridged by π-conjugated bispyridine linkers. In this case, the biological function arises from interfacial recognition rather than photocatalysis. The positively charged Ag-cluster frameworks interact electrostatically with negatively charged DNA backbones, while the acetylenic aromatic linkers provide π-rich surfaces capable of engaging nucleobase-containing strands. These combined interactions allow the frameworks to adsorb single-stranded DNA probes stained with SYBR Green I and suppress their high background fluorescence. Upon hybridization with complementary target DNA, the double-stranded product becomes less susceptible to framework-mediated quenching, restoring fluorescence and improving signal contrast (Figure e). Ag₁₄bpa increased the signal-to-noise ratio to ca. 42.5 at 5 μg mL^–1, whereas Ag₁₂bpeb reached ca. 32.5 at 10 μg mL^–1, corresponding to about a 2.5-fold enhancement over the SCAM-free assay (Figure f). This work positions Ag NCMOFs as programmable diagnostic interfaces, where crystallinity, surface charge, and linker π-character are used to improve DNA readout without covalent labeling.

6. Identifying Challenges and Charting the Road Ahead

6.1. From Decorative Porosity to Functional Porosity

One of the most persistent yet underappreciated limitations of Ag NCMOFs originates from the very feature that makes them unique: the NC node itself. Unlike conventional MOFs, where lattice points are typically single metal ions or compact SBUs, Ag NCMOFs employ atomically precise silver clusters surrounded by bulky thiolate, chalcogenolate, carboxylate, phosphine, or mixed ligand shells. Although these ligands are indispensable for stabilizing the silver core, they occupy a substantial fraction of the framework volume and frequently obstruct pore apertures. Consequently, many Ag NCMOFs exhibit relatively modest BET surface areas despite possessing visually open crystal structures. In numerous cases, large cluster dimensions, dense ligand coverage, framework interpenetration, and inefficient packing collectively reduce accessible free volume, thereby limiting guest diffusion, adsorption capacity, and active-site accessibility. As a result, the majority of reported Ag NCMOFs have naturally gravitated toward photoluminescence and sensing applications, where extensive porosity is not strictly required. In contrast, applications that critically depend on mass transportgas storage, molecular separations, heterogeneous catalysis, ion transport, electrocatalysis, and energy storageremain comparatively underdeveloped. Overcoming this bottleneck will require a transition from merely constructing porous Ag NCMOFs toward engineering functionally accessible porosity. Future efforts may benefit from the use of ultrarigid multitopic linkers, mesopore-generating topologies, hierarchical pore architectures, and cluster surface engineering strategies that minimize steric congestion without compromising cluster stability. Particularly attractive is the prospect of employing atomically precise Ag clusters as vertices in highly connected 3D frameworks analogous to modern ultraporous MOFs and covalent organic frameworks (COFs), thereby decoupling cluster size from pore accessibility. Such advances could transform Ag NCMOFs from predominantly optical materials into genuine porous platforms capable of addressing challenges in catalysis, separation science, and molecular transport.

6.2. Toward Predictive and Data-Driven Ag NCMOF Discovery

Despite the remarkable structural diversity achieved thus far, the synthesis of Ag NCMOFs remains dominated by empirical experimentation. Reaction outcomes often depend sensitively on solvent composition, ligand exchange kinetics, silver precursor speciation, counterions, modulators, crystallization rates, and cluster stability windows. Consequently, discovering a new Ag NCMOF frequently involves extensive trial-and-error screening with limited predictive guidance. The emergence of machine learning, artificial intelligence (AI), and data-driven materials discovery offers a transformative opportunity to overcome this challenge. Future Ag NCMOF research would benefit enormously from the creation of curated databases containing cluster nuclearity, ligand identity, solvent systems, synthetic conditions, framework topology, photophysical properties, stability metrics, and application performance. Such datasets could serve as training platforms for machine-learning models capable of predicting crystallization outcomes, framework dimensionality, pore characteristics, luminescence behavior, charge-transport properties, and catalytic activity. More importantly, AI should not merely accelerate synthesis optimization. The true opportunity lies in inverse design. Rather than asking which structure emerges from a given set of reagents, future workflows could begin with a target propertysuch as near-infrared emission, high conductivity, room-temperature phosphorescence, circularly polarized luminescence, or selective analyte recognitionand use generative algorithms to propose cluster compositions, linker architectures, and topological arrangements likely to achieve that objective. Graph neural networks, crystal language models, Bayesian optimization, autonomous experimentation, and closed-loop robotic synthesis platforms could collectively shift Ag NCMOF discovery from empirical exploration toward predictive materials engineering. Such an approach may prove particularly valuable because the combinatorial design space of Ag NCMOFs is enormous, encompassing cluster nuclearity, ligand-shell chemistry, linker functionality, dimensionality, topology, defects, guest molecules, and framework dynamics.

6.3. Expanding the Structural Toolbox Beyond Single-Crystal X-ray Diffraction

A remarkable strength of the Ag NCMOF field is that a large fraction of reported materials possess SCXRD structures. This level of atomic precision has enabled unprecedented insight into cluster nuclearity, ligand arrangements, framework topology, and host–guest interactions. Nevertheless, SCXRD imposes significant practical constraints. Large, defect-free crystals are often difficult to obtain, especially for metastable phases, nanoscale crystallites, thin films, exfoliated layers, mixed-component frameworks, and device-integrated materials. Electron diffraction (ED), particularly 3D electron diffraction (3D ED), microcrystal electron diffraction (MicroED), and continuous-rotation electron diffraction techniques, is poised to become a transformative complement to SCXRD. Unlike conventional X-ray crystallography, ED can solve structures from crystals several orders of magnitude smaller than those required for SCXRD, opening access to phases that may never be obtainable as macroscopic single crystals. This capability is especially relevant for Ag NCMOFs, where kinetic products, defect-rich materials, ultrathin sheets, and nanocrystalline frameworks are increasingly important. The future will likely rely on a synergistic SCXRD–ED workflow. SCXRD will remain the gold standard for high-precision atomic refinement, while ED will dramatically expand the accessible structural landscape. Combined with advanced STEM imaging, electron tomography, in situ diffraction, pair-distribution-function analysis, and operando spectroscopies, these approaches could reveal how Ag NCMOFs evolve during crystallization, guest uptake, catalysis, photoexcitation, and structural transformation. Ultimately, understanding dynamic structure–property relationships may become as important as determining static crystal structures.

6.4. From Luminescence Phenomena to Deployable Sensing Technologies

Photoluminescence-based sensing currently represents the most mature application domain of Ag NCMOFs. However, the overwhelming majority of demonstrations remain laboratory-scale proof-of-concept studies based on suspended powders, fluorescence titrations, or idealized analyte environments. Translation into deployable sensing technologies remains surprisingly limited. Future progress will require moving beyond analyte recognition toward complete sensing systems. Integration of Ag NCMOFs into thin films, membranes, fibers, paper-based platforms, flexible electronics, microfluidic devices, smartphone-readable sensors, wearable technologies, and wireless sensing architectures should become a major priority. Equally important is improving operational robustness under realistic environmental conditions involving humidity, competing interferents, variable temperatures, and long-term cycling. Particularly exciting opportunities exist at the intersection of Ag NCMOF photophysics and modern electronics. The emergence of Ag NCMOF-based LEDs, memory devices, transistors, and chiroptical materials suggests that sensing, signal processing, and information storage may eventually be integrated within the same framework material. Such multifunctional devices could transform Ag NCMOFs from passive reporters into active sensing platforms capable of detection, amplification, processing, and response.

6.5. Multivariate Ag NCMOFs: The Next Frontier in Functional Complexity

Most reported Ag NCMOFs rely on a single cluster node and a single linker type. Although this approach has yielded remarkable structural diversity, it captures only a small fraction of the design space available to reticular chemistry. The next major leap may arise from multivariate Ag NCMOFs incorporating multiple linkers, multiple cluster types, multiple chromophores, multiple catalytic centers, or combinations thereof within one framework. Such materials could enable simultaneous integration of sensing, catalysis, charge transport, chirality, and molecular recognition. For example, one linker may function as a photosensitizer, a second as an analyte-recognition unit, while the Ag cluster itself serves as an emission center. Similarly, frameworks containing both Ag clusters and catalytically active heterometallic clusters may facilitate tandem catalytic transformations inaccessible to single-component systems. The central challenge will be controlling spatial distribution and avoiding statistical disorder. Advances in reticular synthesis, postsynthetic modification, linker exchange, and AI-guided framework design may provide practical routes toward precisely programmed multivariate architectures.

6.6. Emerging Opportunities Beyond Luminescence and Sensing

The most transformative future applications of Ag NCMOFs may ultimately emerge outside their current comfort zone. Several opportunities appear especially compelling. First, the coexistence of atomically precise metallic nodes and crystalline periodicity positions Ag NCMOFs as attractive candidates for quantum-confined electronic materials, neuromorphic devices, memristors, and information-storage technologies. Second, the combination of tunable excited states, heavy-atom effects, and long-lived charge-separated states suggests unexplored opportunities in photocatalytic CO₂ reduction, nitrogen fixation, solar-energy conversion, and photoredox chemistry. Third, the recent emergence of conductive and semiconducting Ag NCMOFs raises the possibility of framework-based thermoelectrics, photodetectors, and optoelectronic circuitry. Fourth, the inherent antimicrobial activity of silver, combined with framework programmability, may enable smart biomedical coatings, antimicrobial implants, responsive wound dressings, theranostic materials, and integrated diagnostic platforms. Finally, the precise arrangement of silver atoms within periodic architectures may create opportunities in plasmonics, nonlinear optics, quantum photonics, and photon-management technologies that remain almost completely unexplored.

6.7. Concluding Outlook: From Cluster Frameworks to Functional Matter

The future of Ag NCMOF research will likely be defined not by the discovery of ever-larger clusters or ever-more-complex topologies, but by the ability to establish predictive relationships between atomic structure, framework architecture, and collective functionality (Figure ). Viewed collectively, the studies discussed throughout this Review suggest a hierarchical design framework for future Ag NCMOFs. At the atomic level, cluster nuclearity, geometry, metal–metal interactions, and ligand-shell composition define the intrinsic electronic structure, stability, and accessible coordination vectors of the Ag node. At the reticular level, linker denticity,

12.

Blueprint for future directions in Ag NCMOF research.

directionality, rigidity, length, and electronic character translate these vectors into specific dimensionalities and topologies while simultaneously regulating cluster–linker electronic communication. Framework rigidity, intercluster separation, pore accessibility, and the local guest environment then determine how efficiently these molecular features are expressed as excited-state stabilization, energy or charge transfer, analyte recognition, mass transport, or catalytic accessibility. Accordingly, optimal Ag NCMOF design should not maximize any single structural parameter in isolation, but rather balance cluster stability with surface accessibility, framework rigidity with stimulus responsiveness, and structural connectivity with functional porosity. The central design principle that emerges is therefore one of multiscale co-programming: the Ag cluster, protecting shell, linker, topology, and pore environment should be treated as electronically and structurally coupled components whose collective organization is selected according to the targeted function. The field now stands at a transition point. Early efforts focused primarily on demonstrating that atomically precise Ag nanoclusters could be reticularized. The next phase must focus on understanding and exploiting the emergent phenomena that arise from reticularization itself. As advances in AI, electron diffraction, operando characterization, multivariate framework design, and device integration converge, Ag NCMOFs are poised to evolve from fascinating luminescent cluster solids into a broader class of programmable functional matter capable of addressing challenges in sensing, catalysis, electronics, photonics, energy, and biomedicine.

Glossary

Vocabulary Section

Reticularized silver nanoclusters

Atomically defined silver nanoclusters incorporated as structurally integral building units of periodic extended architectures through coordination, ligand-mediated, or direct intercluster connectivity; reticularization couples the intrinsic electronic and photophysical characteristics of the cluster with the connectivity and environment of the surrounding lattice

Nanocluster metal–organic frameworks (NCMOFs)

Crystalline extended frameworks in which atomically precise, ligand-protected metal nanoclusters serve as framework nodes rather than conventional single-metal ions or small polynuclear secondary building units; their properties therefore emerge from the interplay among cluster nuclearity and electronic structure, surface ligands, reticular linkers, and framework organization

Cluster–linker interactions

Electronic, photophysical, and structural coupling between nanocluster nodes and the organic components that connect them within a reticular framework; these interactions can regulate charge and energy transfer, excited-state populations, emission pathways, and responses to external stimuli

Framework-rigidified emission

Enhancement or modification of nanocluster luminescence resulting from restriction of structural and molecular motions upon incorporation into an ordered framework; reduced vibrational and rotational freedom can suppress nonradiative excited-state relaxation and thereby promote more efficient or persistent emission

Guest-programmed photophysics

Modulation of the excited-state behavior and optical output of a reticularized nanocluster framework through interactions with molecules or ions accommodated within or interacting with the lattice; guest binding, diffusion, or exchange can perturb local environments and cluster–linker interactions, producing changes in emission intensity, wavelength, lifetime, or excited-state pathways

T.I. and S.D. conceived the scope and organization of the Review, conducted the literature analysis, and wrote the manuscript. T.I. prepared the figures and graphical materials. S.D. coordinated the conceptual development and manuscript revision. T.K. critically reviewed and refined the scientific content. Y.N. provided scientific guidance and supervision and critically revised the manuscript. All authors reviewed and approved the final manuscript.

The authors declare no competing financial interest.

Published as part of Precision Chemistry special issue “Precision Chemistry for Metal-Organic Frameworks (MOFs)”.