Copper-Based Metal–Organic Frameworks for Sustainable Catalysis: Mechanistic Insights, Stability, and Emerging Research Directions

Abstract

Metal–organic frameworks (MOFs) have emerged as a versatile class of porous crystalline materials due to their tunable structures, large surface areas, and diverse functionalities. Among them, copper-based MOFs (Cu-MOFs) are of particular interest because of the redox activity of copper centers, flexible coordination chemistry, and high affinity for various organic linkers. These features make Cu-MOFs promising candidates for a wide range of applications spanning catalysis, energy conversion and storage, and chemical sensing. This review highlights recent advances in the synthesis and design strategies of Cu-MOFs, including conventional solvothermal and hydrothermal routes, microwave- and sonochemical-assisted methods, electrochemical synthesis, and postsynthetic modifications. Particular emphasis is placed on the ability of these synthetic approaches to tune particle size, morphology, porosity, and stability, which, in turn, dictate their functional performance. The catalytic applications of Cu-MOFs are critically examined, with a focus on photocatalysis, electrocatalysis, and heterogeneous catalytic processes for pollutant degradation, hydrogen production, and carbon dioxide reduction. In the context of energy storage, the integration of Cu-MOFs into supercapacitors and batteries is discussed, highlighting their roles in enhancing the capacity, conductivity, and cycling stability. Furthermore, the potential of Cu-MOFs as sensitive and selective sensing platforms for gases, biomolecules, and environmental pollutants is explored, underscoring their versatility beyond catalytic applications. Despite rapid progress, key challenges remain in scaling up the synthesis, ensuring long-term structural stability, and integrating Cu-MOFs into practical devices. Future research directions include the development of cost-effective green synthesis methods, hybrid composite materials with enhanced conductivity, and defect and interface engineering to tailor activity and durability. Overall, Cu-MOFs represent a highly adaptable platform whose continued advancement may significantly impact sustainable energy technologies, environmental remediation, and next-generation sensing systems.

1. Introduction

Metal–organic frameworks (MOFs) are an important and unique class of crystalline porous materials composed of inorganic metal nodes or clusters coordinated to multidentate organic linkers. − This combination of inorganic and organic components creates a hybrid architecture that offers an exceptional degree of structural and functional tunability. By altering the nature of the metal centers, linkers, and connectivity, researchers can precisely engineer the MOF properties to match a specific application. Such flexibility has made MOFs highly attractive for diverse uses, including gas storage and separation, heterogeneous catalysis, chemical sensing, drug delivery, and energy storage and conversion. − Over the past two decades, the field has grown rapidly, evolving from an emerging concept into a vast and mature research area with thousands of reported structures. This growth has been enabled by advances in synthetic chemistry, postsynthetic modification (PSM) techniques, and a deeper understanding of structure–property relationships.

Within this broad material family, copper-based MOFs (Cu-MOFs) represent one of the most studied and functionally versatile subgroups. The scientific interest in Cu-MOFs stems from several intrinsic properties of copper and its coordination chemistry. First, copper is a redox-active transition metal capable of reversibly cycling between +1 and +2 oxidation states and, in certain environments, even accessing the +3 state. This redox flexibility enables Cu-MOFs to participate in a wide variety of electron-transfer processes, which is crucial for applications in oxidation–reduction catalysis and electrocatalysis. Second, Cu-MOFs often feature robust and well-defined secondary building units (SBUs), the most common being the binuclear paddlewheel cluster [Cu₂(O₂CR)₄]. This motif not only provides mechanical and thermal stability but also supports large surface areas and permanent porosity, which are key requirements for adsorption-driven processes.

A particularly important feature of many Cu-MOFs is the presence of coordinatively unsaturated sites (CUS). These open metal sites are generated when terminal ligands, often solvent molecules, are removed during the activation process. The exposed Cu²⁺ centers can directly interact with guest molecules, enabling strong adsorption, specific binding, and catalytic activation. The presence of these uniform and accessible sites often results in higher activity and selectivity compared with traditional heterogeneous catalysts, where metal sites may vary in structure and accessibility.

From a synthetic standpoint, Cu-MOFs are highly versatile. They can be prepared under a wide range of conditions, including mild solvothermal and hydrothermal methods, electrochemical synthesis, microwave-assisted methods, and even room-temperature self-assembly. This adaptability not only facilitates scale-up but also allows for precise control over the morphology. Reported morphologies include nanoparticles, nanosheets, nanorods, hollow microspheres, and hierarchical structures with interconnected pores. Morphological tuning plays a crucial role in optimizing properties such as active site exposure, diffusion pathways, and light-harvesting capability. Furthermore, Cu-MOFs can be incorporated into composites with other functional materials, enabling synergistic effects. For example, integrating Cu-MOFs with carbon nanotubes, graphene, or conductive polymers can improve their electrical conductivity and mechanical strength, making them suitable for advanced electrochemical applications.

MOF-derived materials, like metal oxides and sulfides, are used in lithium-, sodium-, and zinc-ion batteries to improve energy capacity, cycle life, and conductivity. , In fuel cells, MOFs serve as catalysts or ion-conducting membranes, enhancing the reaction efficiency. Their tunable structure makes them ideal for optimizing performance in clean energy applications. , MOFs are highly effective in removing pollutants from air and water. They can capture toxic heavy metals like Pb²⁺, Cr⁶⁺, and Hg²⁺ from contaminated water and break down organic pollutants such as dyes and pesticides using light-driven processes. , MOFs also purify air by adsorbing harmful gases like VOCs, SO₂, and NOx, improving environmental and human health. , MOFs and their derivatives (e.g., carbon oxides) are promising catalysts for water splitting to produce green hydrogen. , MOF-based materials, such as metal phosphides, oxides, and sulfides, enhance reaction rates due to their good conductivity, stability, and tunable properties. These features make them ideal for clean hydrogen production in sustainable energy systems − (See Figure ).

1.

Diagram of the application of MOFs.

Although numerous reviews have summarized the synthesis and catalytic applications of Cu-based MOFs (Cu-MOFs), most of them emphasize either specific catalytic reactions (e.g., photocatalysis or electrocatalysis) or general structural overviews without establishing mechanistic relationships. In contrast, the present review provides a comprehensive, mechanism-oriented, and future-focused analysis of Cu-MOFs as catalytic platforms for sustainable energy and environmental applications. The unique contributions of this review, unlike prior reviews that mainly catalogue catalytic data, systematically correlate active site chemistry, electron-transfer pathways, and intermediate evolution with catalytic performance across thermal, electrochemical, and photocatalytic systems.

The review introduces a comparative framework linking synthesis methods (solvothermal, microwave, sonochemical, electrochemical, and mechanochemical) to crystal quality, energy efficiency, and structural properties, highlighting how these factors govern catalytic behavior. It provides, for the first time, a consolidated summary of stability-determining factorsmetal nodes, ligand basicity, pore hydrophobicity, and defect concentrationand critically evaluates enhancement strategies such as heterometal doping, PSM, and hydrophobic surface functionalization. This review proposes a unified mechanistic paradigm applicable to all major catalytic regimes (thermal, electro-, and photocatalytic), integrating in situ spectroscopic evidence and theoretical findings to describe Cu²⁺/Cu⁺ cycling, charge migration, and intermediate stabilization. The outlook section moves beyond general challenges and outlines specific, actionable research priorities, including the development of stimuli-responsive Cu-MOFs with switchable active sites, creation of hybrid bio-MOFs catalytic systems, application of machine learning-guided screening and design of Cu-MOFs, and integration into device-scale catalytic architectures for sustainable technologies. Together, these aspects make this review not merely a summary but a critical synthesis and conceptual advancement in understanding the structure–function–mechanism relationship of Cu-MOFs for sustainable catalysis.

2. Structural Advantages of Cu-MOFs

MOFs are especially promising as heterogeneous catalysts because of their high surface area, tunable pore sizes, and the ability to incorporate catalytically active metal centers within a porous crystalline framework. These features facilitate better diffusion of reactants, enhance active site accessibility, and allow for precise control over the reaction environment, leading to improved catalytic efficiency and product selectivity. Additionally, the modularity of MOFs enables the design of multifunctional materials that can mimic the enzymatic oxidation processes. Therefore, MOFs provide an excellent platform for the development of green, efficient, and reusable catalytic systems for the selective oxidation of ethylbenzene using environmentally benign oxidants such as hydrogen peroxide or organic peroxides. MOFs are crystalline porous materials composed of metal ions or clusters connected by organic ligands. ,

Metal nodes (clusters or ions) form the backbone of MOFs by serving as strong and stable coordination centers that hold the entire structure together. Depending on their oxidation state and coordination preference, metals like Zn²⁺, Cu²⁺, Fe³⁺, Zr⁴⁺, and Al³⁺ can form different structural motifs such as paddle-wheel clusters, octahedral geometries, or highly connected polyhedral units. These variations in geometry strongly influence the final framework architecture, affecting not only the size and shape of the pores but also the overall rigidity and thermal stability of the MOFs. For instance, Zr⁴⁺-based clusters are known to produce extremely stable frameworks (like UiO-series MOFs), while Cu²⁺ paddle-wheel units often result in high porosity and open metal sites suitable for catalysis. Thus, the choice of metal node is a decisive factor in designing MOFs for specific applications.

Organic linkers, in contrast, provide the “bridges” that connect these metal nodes and extend the structure into ordered porous networks. Most commonly, polycarboxylates or nitrogen-containing azoles are used because they can form multiple coordination bonds simultaneously, ensuring robust framework formation. For example, 1,4-benzenedicarboxylate (BDC) creates linear connections, leading to frameworks with uniform channels, while 1,3,5-benzenetricarboxylate (BTC) offers three connection points, resulting in highly branched 3D networks. By varying the length, shape, and functional groups of linkers, researchers can fine-tune the pore dimensions, surface chemistry, and adsorption properties. This flexibility allows MOFs to be engineered for diverse functions, including gas storage (CO₂, H₂, and CH₄), pollutant capture, drug delivery, and heterogeneous catalysis, making them one of the most versatile classes of porous materials (See Figure ).

2.

General schematic for the synthesis of MOFs.

MOFs have emerged as promising candidates for catalytic applications due to their high surface area, tunable porosity, and well-defined active sites. At the nanoscale, MOFs exhibit enhanced catalytic performance due to their large number of accessible active sites and well-structured frameworks, making them ideal for oxidation reactions. ,

MOFs can be categorized based on their structural dimensionality, which influences their properties and applications.

• (I)One-dimensional MOFs (1D MOFs): 1D MOFs are a special class of MOFs where the structure extends in only one direction, forming long, chain-like or rod-like arrangements. In these materials, metal ions or clusters are connected by organic linkers to form linear or zigzag chains. The one-dimensional structure allows electrons to move easily along the chains, making them useful in conductive materials, sensors, and catalysis. While they may not have the high surface area and porosity of 3D MOFs, their simple and flexible structure makes them interesting for specialized applications. ,
• (II)Two-dimensional MOFs (2D MOFs): 2D MOFs are materials where the structure extends in two directions, forming flat, sheet-like layers. In these frameworks, metal ions or clusters are connected by organic linkers to create a network that spreads out like a thin sheet or film. These layers can stack on top of each other, often held together by weak forces like van der Waals interactions or hydrogen bonds. Due to their layered structure, 2D MOFs exhibit unique properties, including a high surface area and easy access to active sites. −
• (III)Three-dimensional MOFs (3D MOFs): 3D MOFs are the most common type of MOFs, where the structure extends in all three directions, length, width, and height, forming a three-dimensional porous network. In these frameworks, metal ions or clusters are connected by organic linkers to form a continuous, stable lattice throughout the material. This creates a rigid, open framework full of pores or cavities. Due to their 3D interconnected porous structure, these MOFs possess large surface areas and high porosity, making them ideal for applications such as gas storage and separation, catalysis, drug delivery, and sensing. Their 3D structure also provides mechanical stability and allows molecules to move inside the pores easily. ,

3. Synthesis Methods of MOFs

Over the past two decades, there has been significant development in the synthesis methods employed to architect MOFs. Various methods have been mentioned briefly, which are listed below.

3.1. Conventional Solvothermal Synthesis

The conventional solvothermal method is one of the most widely used approaches for synthesizing MOFs. In this process, metal salts and organic linkers are dissolved in an appropriate solvent and then placed inside a sealed container, known as a Teflon-lined autoclave. The mixture is heated at elevated temperatures, often between 100 and 250 °C, under autogenous pressure. These conditions allow the metal ions to coordinate with the organic linkers, leading to the gradual nucleation and growth of crystalline MOF structures. The high temperature and pressure inside the autoclave promote the solubility of reactants and enhance the reaction kinetics, resulting in the formation of highly ordered, crystalline MOFs with well-defined pore structures.

One of the primary advantages of this method in MOF synthesis is its ability to produce uniform crystals with controlled size, shape, and porosity, which are crucial for applications, such as gas storage, separation, and catalysis. For example, solvothermal synthesis has been used to create renowned MOFs, such as MOFs-5 (Zn-based) and UiO-66 (Zr-based), both known for their high crystallinity and stability. However, the method also has drawbacks: it typically requires long reaction times (from several hours to days) and consumes large amounts of energy due to the need for continuous heating. Moreover, scaling up solvothermal synthesis can be challenging due to the expensive equipment and the difficulty in maintaining uniform reaction conditions on a larger scale. Cu-Mel is prepared via a hydrothermal reaction by dissolving cuprous chloride and melamine in acetonitrile and then refluxing at 100 °C for 20 h. The resulting solid is collected by centrifugation, washed repeatedly, and dried under vacuum.

3.2. Microwave-Assisted Synthesis Method

Microwave-assisted synthesis is a modern and efficient technique for preparing MOFs, designed to overcome some of the limitations of the conventional solvothermal method. In this approach, metal salts and organic linkers are dissolved in a suitable solvent, and the reaction mixture is subjected to microwave irradiation. The microwaves interact directly with polar molecules or ions in the solution, generating a rapid and uniform heating throughout the mixture. This accelerates nucleation and crystal growth, often leading to the formation of MOFs in just a few minutes or hours, compared to days in solvothermal synthesis.

The main advantages of microwave-assisted synthesis of MOFs include shorter reaction times, higher energy efficiency, and improved control over particle size and morphology. Numerous studies have reported that this method can produce smaller, more uniform nanocrystals, which are particularly useful for applications in catalysis, sensing, and drug delivery. Additionally, the technique allows for fine-tuning of reaction parameters (such as power, time, and temperature) to achieve different crystal sizes or phases. However, the method also has limitations, such as the need for specialized microwave reactors and difficulties in scaling up for large-scale production. Despite this, microwave-assisted synthesis is increasingly popular for rapid screening of MOF materials and for developing nanostructured MOFs with unique properties. The Cu-MOFs were synthesized by dissolving CuCl₂·2H₂O and pyridine-2,6-dicarboxylic acid in water, stirring at 50 °C, and then applying microwave irradiation (300 W, 15 min) to induce crystallization. The product was separated by nanofiltration, washed with ethanol/water, and vacuum-dried for 48 h. For penicillinoate@Cu-MOFs, the prepared Cu-MOFs were further mixed with penicillin under the same microwave conditions, yielding nanocrystals with slightly larger size and higher surface area.

3.3. Sonochemical Synthesis Method

Sonochemical synthesis of MOFs is a method that uses ultrasound waves to accelerate the reaction between metal ions and organic linkers in solution. When high-frequency ultrasound is applied to the reaction mixture, it generates a phenomenon known as acoustic cavitation, characterized by the rapid formation, growth, and collapse of microscopic bubbles within the solvent. The collapse of these bubbles produces localized hot spots with extremely high temperature (∼5000 K) and pressure (∼1000 atm) for very short times, along with intense shock waves and microjets. These extreme conditions enhance the mixing of reactants, speed up nucleation, and lead to the rapid crystallization of MOFs.

The sonochemical method offers several advantages over conventional solvothermal synthesis. It allows the preparation of MOF nanocrystals in a much shorter time (minutes instead of hours or days), often at lower bulk temperatures. The technique also promotes a uniform particle size distribution and smaller crystal sizes, which are valuable for applications such as catalysis, drug delivery, and adsorption, where a high surface area is critical. Moreover, sonochemistry is considered a green and energy-efficient approach as it often eliminates the need for high external heating. However, scaling up sonochemical synthesis remains challenging because maintaining uniform ultrasound energy distribution in large volumes is difficult. Despite this, it is an excellent method for producing nanoscale MOFs with enhanced surface activity and functional properties. The Cu-MOFs were synthesized by mixing aqueous solutions of CuSO₄·5H₂O and 2,6-pyridinedicarboxylic acid, followed by 21 min sonication at 40 °C (175 W) to induce nucleation. The mixture was then aged at room temperature for 4 days, yielding blue mesoporous Cu-MOF nanocrystals (∼50–65 nm) that were confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analyses.

3.4. Electrochemical Synthesis of MOFs

Electrochemical synthesis of Cu-MOFs is a versatile and efficient method that uses an electrochemical cell to generate the required metal ions in situ, eliminating the need for external metal salts. In this approach, a copper electrode (anode) is typically used as the metal source, while an organic linker (such as BDC-1,4-benzenedicarboxylic acid or BTC-benzene-1,3,5-tricarboxylic acid) is dissolved in a suitable solvent/electrolyte solution. When an electric potential is applied, the copper electrode undergoes anodic dissolution, releasing Cu²⁺ ions into the solution. These ions then coordinate with the linker molecules, resulting in the direct formation of Cu-MOFs crystals either in suspension or deposited on the electrode surface.

This method offers several advantages over conventional solvothermal or sonochemical techniques. First, it provides precise control over the reaction by simply tuning the applied voltage, current density, and electrolysis time. Second, it is generally faster and more energy-efficient, producing Cu-MOFs at room temperature or under mild conditions without the need for high-pressure autoclaves. Electrochemical synthesis also enables the direct growth of Cu-MOF films or coatings on conductive substrates, which is highly beneficial for applications in electrochemical sensors, supercapacitors, electrocatalysis, and energy storage. However, the technique requires optimization of parameters (such as electrolyte composition, pH, and current) to obtain crystals with the desired morphology, size, and porosity. Despite these challenges, electrochemical synthesis is considered a green and scalable method for fabricating Cu-MOFs, especially when thin films or nanostructures are desired for device applications. Cu-MOFs were synthesized electrochemically using copper electrodes and terephthalic acid (H₂BDC) in solvents like DMF. Copper ions generated at the anode coordinated with BDC to form 2D layered copper-terephthalate frameworks. The applied current/voltage and solvent choice controlled the layer stacking and whether solvent molecules were intercalated, yielding either compact or more open-channel MOF structures. Cu₃(HHTP)₂ MOFs were synthesized electrochemically by oxidizing copper nanoparticles deposited on interdigitated electrodes in a solution of the organic linker HHTP (2,3,6,7,10,11-hexahydroxytriphenylene). The in situ growth produced uniform, conductive MOF films directly on the electrode surface. These Cu-MOF films were structurally confirmed [SEM, Raman, and X-ray photoelectron spectroscopy (XPS)] and applied as chemiresistive sensors, showing high sensitivity to NO₂ and NH₃ gases

3.5. Mechanochemical Synthesis of MOFs

Mechanochemical synthesis of Cu-MOFs is a solvent-free or minimal-solvent method that relies on mechanical energy (such as grinding, milling, or shearing) to induce the reaction between copper precursors and organic linkers. In a typical procedure, a copper salt [e.g., Cu­(OAc)₂, Cu­(NO₃)₂] and an organic linker (such as BDC or BTC) are placed in a mortar or ball mill and subjected to grinding. The mechanical force breaks intermolecular bonds, increases surface contact, and provides the energy necessary for Cu²⁺ ions to coordinate with the linker, thereby forming the desired Cu-MOF structure. In some cases, a small amount of liquid [called liquid-assisted grinding (LAG)] is added to facilitate the reaction and improve crystallinity.

The mechanochemical route offers several key advantages. It is considered a green and sustainable method, since it requires little or no solvent, reducing the environmental impact compared to solvothermal or electrochemical techniques. The synthesis is typically fast (minutes to hours) and highly reproducible and can be scaled up using ball milling. Mechanochemistry also allows the preparation of Cu-MOFs nanocrystals or amorphous phases with unique properties that may not be achievable through conventional methods. However, this approach has limitations such as difficulties in precisely controlling crystal size, morphology, and long-range crystallinity, which may affect porosity and surface area. Despite these challenges, mechanochemical synthesis has gained significant attention for producing Cu-MOFs for applications in gas storage, catalysis, and environmental remediation, while aligning with the principles of green chemistry (See Table ).

1. Representative Synthesis Methods with Example Cu-MOFs.

example Cu-MOFs/composite	synthesis method	typical precursors and conditions	morphology
HKUST-1 (Cu-BTC)	solvothermal (or RT precipitation)	Cu salt, 1,3,5-BTC; solvent, RT–80 °C; hrs	blue crystalline HKUST-1; paddlewheel SBUs; high porosity ,
Cu-Mel (Cu+ + melamine)	hydrothermal	Cu+ source, melamine; hydrothermal several hours	Cu(I) MOFs; laccase-like nanozyme activity
Cu-CAT on Cu foam (Cu-catecholate)	short solvothermal ligand exchange (70 °C, 10 min)	Preformed Cu(OH)2 nanoneedles; HHTP ligand; water/DMF 10:1	atomically dispersed MOFs nanoarray; grown directly on CF
HPW-2@Cu-MOFs	hydrothermal with HPW loading	Cu(NO3)2: H3BTC = 2:1; HPW 1.2 wt %; 24 h; 200 °C for operation	HPW encapsulated in HKUST-like matrix; enhanced thermal stability
Cu-MOFs/TiO2 composite	solvothermal synthesis + physical mixing or in situ growth	Cu2+ + linker solvothermal to form MOFs; TiO2 nanoparticles combined postsynthesis	heterojunction MOFs/TiO2 for enhanced charge separation
mechanochemically prepared Cu-MOFs	ball-milling/LAG	Cu salt + BDC/BTC; grinding minutes–hours; small LAG solvent	solvent-free, green, fast produces nanocrystalline phases

4. Comparative Evaluation of Cu-MOF Synthesis Methods

Although the previous section provided individual descriptions of solvothermal, microwave, sonochemical, electrochemical, and mechanochemical methods, a direct comparison of their synthesis parameters, energy efficiency, and structural outcomes is essential to highlight their relative merits and application scopes. Table presents a comparative overview of these synthesis routes for Cu-MOFs, emphasizing reaction time, energy demand, morphological control, scalability, and the resulting impact on framework quality and functionality.

2. Comparative Evaluation of Cu-MOF Synthesis Methods.

synthesis method	reaction conditions/time	energy consumption	crystallinity and morphology control	major advantages	key limitations	typical applications/suitable scenarios	influence on structural and functional properties
conventional solvothermal/hydrothermal	elevated temperature (100–250 °C), autogenous pressure, 6–72 h	high (requires prolonged heating and sealed reactors)	produces highly crystalline, defect-free structures; excellent morphology control	most established method; high yield; reproducible; suitable for large, porous frameworks	long synthesis duration; high energy cost; limited scalability due to batch reactors; solvent waste	Used for high-quality crystalline Cu-MOFs (e.g., HKUST-1, Cu-BTC) for gas storage, catalysis, and adsorption	generates well-ordered frameworks with uniform Cu–Cu paddlewheel SBUs and high porosity; ensures thermal stability and reproducibility
microwave-assisted synthesis	mild temperature (60–180 °C); short duration (5–60 min)	low to moderate (efficient volumetric heating)	produces smaller, uniform nanocrystals; enhances nucleation rates	rapid, energy-efficient; uniform heating; controllable particle size; reduces reaction time	requires specialized reactor; difficult to scale up; may produce phase heterogeneity at high power	Suitable for nanostructured Cu-MOFs for catalysis, sensing, and adsorption	generates fine particles with large surface areas; increases active site accessibility; enhances electron/ion transport due to nanoscale size
sonochemical synthesis	ambient to moderate temperature (∼30–60 °C); reaction time 5–30 min	low (energy from ultrasound cavitation)	produces nanocrystals (20–100 nm) with uniform distribution	fast, green, solvent-efficient; low bulk temperature; no need for high-pressure vessels	nonuniform ultrasound distribution in large volumes; limited crystallinity	Useful for nanoscale Cu-MOFs for drug delivery, adsorption, photocatalysis	generates highly dispersed, small particles with defect-rich surfaces; promotes open metal sites and enhances catalytic activity
electrochemical synthesis	ambient conditions; controlled voltage (1–5 V); 10 min–2 h	very low (electrochemical energy only)	controlled film formation or powder deposition; variable crystallinity	room temperature, scalable, solvent-saving; allows direct growth on electrodes; tunable by potential/current	requires optimization of electrolyte composition and parameters; may yield thin coatings	Ideal for electrochemical sensors, supercapacitors, electrocatalysts	produces conductive Cu-MOFs films with controlled orientation; enables mixed-valence Cu species; enhances charge transport and surface reactivity
mechanochemical (ball-milling/LAG)	ambient temperature; mechanical grinding (minutes–hours)	very low (mechanical force only; minimal solvent)	produces nanocrystalline or amorphous structures	solvent-free, green, rapid, scalable; minimal environmental footprint	limited crystallinity; poor long-range order; difficult to achieve uniform morphology	large-scale green synthesis, adsorbents, and catalysis requiring high defect density	generates defect-rich frameworks; tunable porosity via liquid-assisted grinding; promotes catalytic reactivity but reduces structural order

Each synthesis method imparts distinct structural, morphological, and functional attributes to Cu-MOFs that directly affect their catalytic, electrocatalytic, and photocatalytic behavior. The solvothermal and hydrothermal methods remain the benchmark approaches for producing highly crystalline Cu-MOFs with uniform pore architectures and well-defined paddlewheel Cu₂(O₂CR)₄ units. High temperature and pressure facilitate slow nucleation and growth, yielding defect-free structures with large specific surface areas (500–1800 m² g^–1). However, their energy-intensive and time-consuming nature, combined with batch reactor limitations, restricts their scalability. These materials typically show superior chemical stability and well-preserved porosity, making them ideal for fundamental catalytic studies and gas adsorption. The microwave-assisted synthesis requires microwave heating to induce rapid and homogeneous nucleation by directly coupling electromagnetic energy into the reaction medium. The resulting nanocrystalline Cu-MOFs (often 50–200 nm) display higher defect densities and more exposed active Cu²⁺ sites, which improve redox activity and charge transfer efficiency. Such MOFs demonstrate superior catalytic and sensing performance. However, high-power microwave exposure can sometimes lead to uneven crystal growth or decomposition of linkers if not carefully optimized.

The sonochemical synthesis requires the ultrasound-induced cavitation, which generates localized high-temperature (5000 K) and high-pressure (1000 atm) microenvironments, promoting rapid bond formation and crystal nucleation. The resulting Cu-MOFs often exhibit mesoporous or hierarchical structures with abundant coordinatively unsaturated sites (CUS). The process is environmentally friendly and energy-saving, although large-scale uniform energy distribution remains a technical hurdle. The Electrochemical Synthesis requires that the Cu²⁺ ions be generated in situ via anodic dissolution of a copper electrode, which then reacts with organic linkers. This method offers exceptional control over film thickness, morphology, and oxidation state (Cu⁺/Cu²⁺ ratio), which is critical for applications such as CO₂ reduction, oxygen evolution reaction (OER)/hydrogen evolution reaction (HER) catalysis, and gas sensing. It also enables direct growth of Cu-MOF films on conductive substrates, bypassing postdeposition steps. Nevertheless, product crystallinity can vary depending on the current density and electrolyte type.

The mechanochemical synthesis represents a sustainable alternative, relying on solid-state grinding or ball-milling with minimal or no solvent. This approach drastically reduces the reaction time and environmental impact while offering easy scalability. The resulting materials, although less crystalline, often exhibit higher defect concentrations, which can enhance the catalytic and adsorption behavior. LAG can partially recover the crystallinity and improve pore connectivity. Mechanochemical Cu-MOFs thus bridge green synthesis and functional material design, particularly for adsorption and low-cost catalytic processes.

5. Stability of Cu-MOFs: Influencing Factors and Enhancement Strategies

The stability of Cu-MOFs is a key consideration that determines their viability for catalytic, electrocatalytic, and photocatalytic applications. Although Cu-MOFs offer high surface area and tunable porosity, they often suffer from limited thermal, chemical, and aqueous stability, primarily due to hydrolysis of Cu–O bonds and framework collapse under harsh conditions. Understanding the factors that influence their structural robustness is, therefore, critical for rational design.

The intrinsic coordination geometry of copper significantly affects the framework resilience. Most Cu-MOFs adopt the paddlewheel [Cu₂(O₂CR)₄] structure, which, while beneficial for porosity, contains labile Cu–O bonds prone to hydrolysis in moist environments. Replacing part of the Cu²⁺ ions with higher-valent or more stable metals (Zr⁴⁺, Ce⁴⁺, Ni²⁺, or Al³⁺) can reinforce structural integrity through stronger metal–ligand bonding. Bimetallic frameworks (e.g., Ni–Cu, Ce–Cu, or Fe–Cu) have shown remarkable improvement in both hydrothermal and redox stability because of the synergistic strengthening of metal–oxygen linkages.

5.1. Influence of Organic Linkers

The nature and basicity of the organic linker determine the coordination strength and the overall robustness of the framework. Carboxylate-based linkers (e.g., BTC and BDC) form moderately strong Cu–O bonds but are susceptible to exchange with water molecules. In contrast, N-donor linkers, such as imidazoles, triazoles, and pyridines, form stronger Cu–N bonds, offering greater resistance to hydrolysis. Moreover, the incorporation of mixed ligands (e.g., BTC + BDC or BDC + bipyridine) can enhance both structural rigidity and electronic communication, leading to an improved catalytic durability.

5.2. Pore Surface Chemistry and Environment

Hydrophilicity within the pores plays a decisive role in determining water tolerance. Hydrophilic frameworks attract water molecules that coordinate to open Cu²⁺ sites, initiating hydrolysis. To mitigate this, surface functionalization with hydrophobic groups (−CH₃, −CF₃, and −F) or encapsulation with hydrophobic coatings (e.g., PDMS, SiO₂, and MOF-on-MOF shells) can substantially enhance water resistance. For instance, SiO₂-coated Cu-BTC exhibits minimal degradation after prolonged exposure to 80% humidity, while uncoated samples lose crystallinity within hours.

5.3. Role of Morphology and Defects

Defect engineering, although beneficial for enhancing active-site density, can compromise stability if excessive. Nanocrystalline Cu-MOFs with large surface areas possess more coordinatively unsaturated sites that facilitate water ingress and ligand displacement. Controlled crystal growth under solvothermal or postannealing conditions enhances lattice ordering and reduces defect-induced degradation. Thus, a trade-off exists between maximizing catalytic activity and ensuring structural robustness.

5.4. Post-synthetic and Composite Approaches

Several PSM techniques have been successfully employed to enhance stability, like incorporating secondary metals (e.g., Ce, Ni, and Zr), which introduces stronger metal–ligand bonds and modifies the electronic environment to resist oxidation. Encapsulating Cu-MOFs with conductive or protective layers (graphene oxide, TiO₂, and polydopamine) prevents hydrolysis and enhances mechanical durability. Embedding Cu-MOFs into polymers or carbon frameworks (EVA, PAN, or CNTs) imparts flexibility, chemical resistance, and better dispersion of active sites.

5.5. Environmental and Operational Factors

Operational conditions, such as temperature, humidity, and pH, strongly influence structural retention. Most Cu-MOFs maintain integrity up to 250–300 °C but degrade rapidly under strongly acidic or basic environments. Activation under inert or vacuum conditions can remove weakly bound solvents and enhance the framework rigidity. During catalytic or electrochemical operation, continuous monitoring of Cu valence states and ligand integrity via in situ XPS or PXRD is crucial to correlate activity with structural evolution (See Table ).

3. Influencing Factors and Enhancement Strategies for Enhancing Cu-MOF Stability.

category	influencing factors/mechanism	effect on stability	representative examples/evidence	enhancement strategies
metal nodes	coordination geometry and oxidation state of CuCu2+ in paddlewheel clusters [Cu2(O2CR)4] prone to hydrolysis; Cu+ species less stable under oxidation	determines framework rigidity and moisture sensitivity. Cu2+–carboxylate bonds are moderately labile in water	HKUST-1 (Cu-BTC) decomposes in humid air due to hydrolysis of Cu–O bonds; Cu-BDC frameworks are more stable due to denser packing	replace labile Cu2+ with mixed-metal nodes (Ni, Zr, Ce, Al) or introduce heterometallic clusters to improve coordination rigidity and redox stability
organic linker type	basicity and denticity of linkersstronger coordination (imidazolates, phosphonates) yields higher hydrolytic resistance than weak carboxylates	determines resistance to ligand displacement and hydrolysis	ZIF-67 and Cu–imidazolate MOFs show superior aqueous stability vs Cu-BTC	use N-donor linkers (triazoles, imidazoles, pyridines) or mixed linkers (BDC + BTC) to reinforce coordination and hydrophobicity
pore environment	hydrophilicity, pore size, and guest molecules influence water adsorption and hydrolysis rate	hydrophilic or open pores accelerate degradation via H2O coordination to Cu2+	HKUST-1 collapses in humidity; surface-modified HKUST-1@SiO2 remains intact	functionalize pores with hydrophobic groups (−CH3, −F, −CF3) or coat with polymeric/covalent layers to reduce moisture diffusion
crystal morphology and defect density	nanocrystals or thin films have high surface energy and exposed sites, making them less stable	smaller particles exhibit faster degradation due to higher surface-to-volume ratios	nanoscale Cu-MOFs degrade faster in aqueous media than microcrystalline counterparts	control morphology via solvothermal methods; postsynthetic annealing to improve crystallinity and remove labile surface ligands
post-synthetic modifications (PSM)	ligand exchange, metal doping, or surface coating	can either stabilize (by strengthening coordination) or destabilize (if mismatched)	Ce-doped Cu-MOFs show enhanced oxidative and hydrothermal stability; polydopamine-coated Cu-BTC is stable in water for >30 days	introduce secondary metals (Zr, Fe, Ce, Ni) or hybrid shells (graphene oxide, TiO2, polymer coatings)
external environment	temperature, humidity, pH, and solvent exposure	high temperature (>250 °C) or acidic conditions can collapse Cu–O networks	Cu-BTC decomposes >300 °C; Cu-BDC is stable up to ∼350 °C	apply activation under inert atmosphere; select solvents (ethanol, DMF) with minimal Cu2+–ligand exchange tendency

6. Expanding Cu-MOF Functionality

Over the past few years, several engineering strategies have emerged to enhance the performance of Cu-MOFs beyond their intrinsic capabilities. These approaches are focused on tailoring the electronic structure, surface chemistry, morphology, and composite architecture to meet the specific demands of catalysis, energy storage and conversion, and sensing. Introducing a second metal into the Cu-MOF framework can profoundly alter their catalytic and adsorption properties by creating synergistic interactions between different metal centers. A secondary metal can modify the electron density of Cu sites, improving the redox cycling and catalytic activity. The modularity of MOFs design also allows incorporation of secondary metals (e.g., Ni, Y, and Ce) to create bimetallic Cu-MOFs with enhanced catalytic performance through synergistic effects. For example, Y–Cu-MOFs integrated into carbon paste electrodes showed significantly enhanced dopamine sensing performance, attributed to synergistic electron transfer between yttrium and copper sites. The Cu–Fe bimetallic Cu-MOFs–Fcdc-20% (Fcdc = 1,1′-ferrocenedicarboxylic acid) achieved a CO selectivity of 97.07% and a CO yield of 8.61 μmol g^–1 h^–1, which is 5.48× higher than the parent Cu-MOFs (1.57 μmol g^–1 h^–1, 81.35%), demonstrating that multiligand design significantly boosts photocatalytic CO₂-to-CO conversion efficiency and selectivity. Bimetallic Cu-BTB-2 wt % Fe MOFs [H₃BTB = 1,3,5-tris­(4-carboxyphenyl) benzene] achieved a CH₄ yield of 32.20 μmol·g^–1·h^–1 with 69.24% selectivity, along with a CO yield of 14.29 μmol·g^–1·h^–1, showing its superior CO₂-to-CH₄ photocatalytic performance compared to other Fe loadings. Mg₀.₄Cu₀.₆-MOFs-74 showed the highest CO₂ uptake of 3.52 mmol·g^–1 under Xe lamp illumination (1.18× and 2.09× higher than Mg- and Cu-MOFs-74, respectively) and achieved a CO yield of 49.44 μmol·gcat^–1 in 8 h, demonstrating superior CO₂ adsorption and photocatalytic reduction performance. Br-functionalized FeCu­(BDC-Br) catalyst achieves a phenol degradation kinetic rate of 0.106 min^–1 under a low catalyst dose. The system operates effectively even in near-neutral pH (4–6) and tolerates 0–50 mg/L humic acid; however, Cl^–, SO₄ ^2–, and PO₄ ^3– at ∼100 mg/L suppress performance.

Modifying the organic linkers with functional groups changes the hydrophilicity, binding affinity, and electronic properties of the MOFs, enabling targeted performance improvements. Amino-functionalized linkers (−NH₂) increase the polar interactions with adsorbates. NH₂-modified ZIF-8 derivatives showed improved dye adsorption capacity [27.5% higher for Congo red (CR)]. In Pd–Cu bimetallic catalysts supported on NH₂-modified Zr-MOFs, the −NH₂ groups enhanced metal precursor binding, promoting uniform particle dispersion, and improved catalytic selectivity. Electron-donating groups like −NH₂ or electron-withdrawing groups like −SO₃H can tune the electron density around Cu²⁺, affecting catalytic turnover frequencies and reaction selectivity. xPd_100–x Cu/UiO-66-NH₂-X catalysts with an optimal 50% NH₂ linker fraction enable the formation of highly active and selective Pd and PdCu catalysts for HMF reduction, while 100% NH₂ content drastically lowers activity by overstabilizing Pd species and hindering bimetallic formation.

Cu-MOFs can be synthesized in diverse morphologiesnanosheets, nanorods, hollow microspheres, and hierarchical assemblieswhich influence surface area, pore accessibility, and diffusion properties. Ultrathin Cu-MOFs molecular layers offer maximum exposure of active sites, facilitating photocatalytic CO₂ reduction. The Cu₂Ce₁O _y -BTC catalyst achieved ∼100% phenol mineralization within 200 min, owing to its larger surface area, higher Ce³⁺ content, and enhanced redox ability for efficient catalytic ozonation. Rod-shaped Cu-MOFs with carboxylate double linkers enhanced photocatalytic degradation by improving charge separation and light harvesting.

In essence, these strategies move Cu-MOF research from simply synthesizing new structures to engineering targeted functionalities by tuning the composition, surface chemistry, morphology, and hybrid architecture. Together, they have expanded the role of Cu-MOFs from conventional adsorbents and catalysts to multifunctional materials capable of addressing challenges in environmental remediation, clean energy, and sensing with high efficiency and specificity.

By virtue of these attributes, Cu-MOFs have become a powerful materials platform bridging fundamental science and practical applications. However, challenges remain in scaling up synthesis, enhancing stability under operational conditions, improving catalytic selectivity, and integrating Cu-MOFs into device architectures. Addressing these issues through rational design will be critical for unlocking the full potential of Cu-MOFs in catalysis, energy conversion/storage, and sensing technologies (Table ).

4. Strategy for Expanding Cu-MOF Functionality.

modification strategy	effect on properties	representative application	example from literature
bimetallic incorporation (e.g.,Y–Cu, Ni–Cu, Ce–Cu)	creates synergistic active sites with complementary catalytic functions. Modifies the electronic structure for improved redox cycling. Increases active site diversity for multiple reaction pathways	dopamine sensing with enhanced electron transfer (Y–Cu-MOFs). Photocatalytic CO2 reduction with directional electron transfer (Cu–Fe MOFs). ,	Y–Cu-MOF-based dopamine sensor
			Fe–Cu–Bimetallic MOFs for CO2 photoreduction reaction and Mg–Cu MOFs for CO2 absorption. −
ligand functionalization (e.g., −NH2, −SO3H)	adjusts hydrophilicity/hydrophobicity for targeted adsorption.- Tunes electron density around Cu2+ to alter catalytic selectivity. Improves the binding of metal precursors for supported catalysts	enhanced dye adsorption (NH2-ZIF-8). Improved Pd–Cu nanoparticle dispersion for selective HMF reduction	NH2-functionalized ZIF-8 for Congo Red removal; NH2-modified Zr-MOFs for Pd–Cu catalysts
morphology control (nanosheets, nanorods, hierarchical microspheres)	increases surface-to-volume ratio and active site exposure. Reduces diffusion path lengths. Alters light absorption and scattering for photocatalysis	ultrathin Cu-MOFs molecular layers for high CO2RR activity. Urchin-like Ce–Cu-MOFs for catalytic ozonation. Rod-shaped Cu-MOFs for enhanced photocatalytic degradation	ultrathin Cu-MOFs MOLs; urchin-like Ce–Cu-BTC;rod-shaped Cu-MOFs for Cr(VI) reduction

7. Applications of Cu-MOFs in Thermal Catalysis

The heterogeneous catalyst is a type of catalyst that is in a physical phase different from that of the reactants. The catalyst is in solid form, while the reactants are liquids or gases. , Heterogeneous catalysts offer several advantages over homogeneous catalysts; one key benefit is their easy separation from the reaction mixture. Heterogeneous catalysts are solid, and the reactants are liquid or gas; the catalyst can easily be separated from the products by simple filtration. This separation makes heterogeneous catalysts more reusable, so we can use them in multiple cycles without catalyst loss, making them cost-effective. Heterogeneous catalysts are more thermally stable, which allows them to be used in high-temperature reactions. It plays a crucial role in advancing green chemistry, as it facilitates easy catalyst recovery and recyclability and minimizes environmental impact. Cu-MOFs were utilized as heterogeneous catalysts in diverse coupling and organic transformations. The authors emphasize the intrinsic advantages of MOFsincluding their facile synthesis, high and tunable porosity, robust frameworks, and recyclabilitywhich make them particularly appealing for catalysis. The review covers a broad spectrum of copper-based MOF architectures incorporating various metal nodes, organic linkers, and structural modifications such as encapsulation or surface coatings. Across these designs, the recurring theme is how the structural engineering of MOFs enhances catalytic active-site accessibility and performance. Within the reviewed literature, Cu-MOFs consistently demonstrate strong performance in key organic coupling reactions, including cross-couplings and C–C and C–N bond formations. Many of these systems exhibit high catalytic yields, often in the 80–99% range, under mild conditions with minimal leaching and maintained activity over multiple reuse cycles. The MOFs’ recyclability and durability, combined with their selectivity and ease of synthesis, position them as cost-effective and efficient catalysts across a variety of coupling transformations. −

Cu-MOF-based porous crystalline catalysts can mimic the enzymatic activity of natural methane monooxygenases. Their periodic frameworks, built from metal nodes (such as Zr, Zn, or Cu) and organic linkers, provide a highly ordered and tunable environment to host copper active sites. Unlike zeolites, MOFs allow greater flexibility in controlling copper nuclearity (mono-, di-, or trinuclear) and local coordination environments, which directly influence methane activation and methanol selectivity. Because methane’s C–H bond is highly stable (438.8 kJ/mol), these engineered copper sites are critical for lowering the activation barrier and avoiding complete oxidation to CO₂.

NU-1000 was used by the Lercher group (2017) to deposit Cu oxide clusters on ZrO₂ nodes via atomic layer deposition. XAS revealed ∼85% Cu²⁺ and ∼15% Cu⁺ species, yielding 45–60% methanol selectivity. Density functional theory (DFT) showed that the active site was a tricopper hydroxide-like cluster with Cu–Cu distances of ∼2.93 Å. Later work (2019) showed that dinuclear copper sites had lower energy barriers and better catalytic activity than mononuclear sites, highlighting the importance of multinuclear clusters. ,

MOFs-808 was used by Baek et al. (2018) and incorporated imidazole groups to anchor Cu­(I) ions, which transformed into bis­(μ-oxo) dicopper sites during activation. These species showed strong Cu–O vibrational bands in Raman spectra and provided high methanol selectivity at 150 °C, showing that the ligand modification of MOFs can stabilize highly active dicopper cores. In ZIF-7, Lee et al. (2022) embedded mononuclear CuN₄ sites, which efficiently cleaved methane C–H bonds and suppressed overoxidation by reducing the intrinsic acidity of the framework. This led to high methanol selectivity, since fewer side products (like formic acid) were formed. ,

From these studies, the nature of the copper sitewhether mono-, di-, or trinuclearplays a decisive role in methane activation. Tricopper and dicopper clusters generally provide higher activity and lower energy barriers, while carefully engineered mononuclear sites can improve the selectivity by avoiding overoxidation. However, Cu-MOFs face a key challenge in thermal stability: unlike zeolites, which can withstand activation temperatures of 400–500 °C, MOFs’ organic linkers degrade under harsh conditions. This makes it harder to replicate the high-temperature pretreatments often used in Cu-zeolite catalysis. Thus, while Cu-MOFs show promise in tailoring active sites and achieving high methanol selectivity under mild conditions, future work needs to focus on designing thermally robust frameworks or hybrid Cu-MOF/oxide materials for practical, scalable methane conversion.

Cu-MOFs have applications in various fields due to the unique properties of MOFs, such as high surface area, tunable porosity, and chemical functionality. , Catalysis is one of the most important and well-known uses of MOFs, especially in solid (heterogeneous) catalytic reactions. MOFs work well as catalysts because they have a very large surface area, which provides many active sites for reactions. Their pore sizes can also be adjusted, allowing specific reactants to reach the catalytic sites more easily and making the reactions more efficient and selective. Also, both the metal centers and the organic parts of MOFs can take part in the reaction, giving them special chemical abilities. , Cu-MOFs have been employed in a wide range of organic transformations, including oxidation, epoxidation, esterification, hydroxylation, and condensation reactions, given their structural flexibility and catalytic potential. ,

Several heterogeneous catalytic systems have been developed for the selective oxidation of ethylbenzene to acetophenone. Among them, the Cu–BTC (HKUST-1) catalyst achieves a conversion rate of 44.92% and a selectivity of 92.53% for the oxidation of ethylbenzene to acetophenone. It operates under solvent-free conditions, which is a positive attribute. The high temperature required (150 °C) for 24 h increases energy consumption, making the process less efficient and more expensive. Overall, catalysts have lower conversion, moderate selectivity, and reduced efficiency in large-scale applications and contribute to increased energy costs. The Cu–BTC–SiO₂ Monolith II catalyst delivers excellent conversion and selectivity rates of >99% under mild conditions. The reaction is not solvent-free; it requires benzonitrile as a solvent, which also adds complexity. These drawbacks reduce its appeal for practical catalytic applications.

Currently, the desulfurization agents employed in dry desulfurization technology face challenges, such as slow reaction rates and low desulfurization efficiency. This study integrates phosphotungstic acid (HPW) into Cu-MOFs using a hydrothermal synthesis method, enhancing the performance of the desulfurization agent through a combination of catalytic oxidation and adsorption. Experimental results indicate that optimal desulfurization effects are achieved when the ratio of copper nitrate trihydrate (Cu­(NO₃)₂) to 1,3-phenyltrifamilic acid (H3BTC) is 2:1, with an HPW addition of 1.2 wt %, and a hydrothermal synthesis duration of 24 h. In a fixed bed desulfurization system, HPW-2@Cu-MOFs demonstrate the best performance at a reaction temperature of 200 °C, achieving a sulfur dioxide removal efficiency nearing 100%, a specific surface area of 612.20 m²/g, a pore volume of 0.2568 cm³/g, and a sulfur capacity of 90.464 mg/g. The incorporation of HPW facilitates the conversion of sulfur dioxide (SO₂) to sulfur trioxide (SO₃) under the influence of surface oxygen (O_α, O_β), resulting in a 10.52% increase in SO₃ content compared with Cu-MOFs. When the flue gas contains a certain concentration of carbon dioxide, HPW-2@Cu-MOFs preferentially react with SO2 due to the adsorption between Cu2+ and SO₂. XPS characterization reveals that W⁵⁺ serves as the active center in HPW; the content of W⁵⁺ in HPW-2@Cu-MOFs was higher than that of others, accounting for 90.6%. Thermogravimetric analysis clearly demonstrates that the thermal stability of Cu-MOFs loaded with HPW has been significantly enhanced.

A Cu-MOF catalyst modified with cetyltrimethylammonium bromide (CTAB) for efficient multicomponent C–S coupling reactions. The researchers synthesized different Cu-MOFs, including Cu-BDC, Cu-BTC, and sulfonated Cu-BDC (Cu-BDC–SO₃Na), and further modified the latter with CTAB to obtain Cu-BDC–SO₃Na-CTAB. The modification introduced long alkyl chains that enhanced the adsorption of organic substrates and reduced mass-transfer resistance during heterogeneous catalysis. Importantly, elemental sulfur (S₈), instead of unstable and malodorous organosulfur reagents, was used as the sulfur source, offering a greener and more stable approach to thioether formation. The catalytic performance was evaluated using iodobenzene, 1-methylindole, and S₈ as the model system. Among the catalysts tested, Cu-BDC–SO₃Na-CTAB achieved the highest yield of 94%, outperforming Cu-BDC (75%), Cu-BTC (62%), and unmodified Cu-BDC–SO₃Na (80%). Optimization studies revealed that the best activity occurred at 110 °C, with a 1:1 molar ratio of the Cu precursor to the organic linker and a 2:1 MOFs-to-CTAB mass ratio. Sodium acetate (NaOAc) proved to be the most effective base, and the reaction required assistance from a base for sulfur activation. The catalyst displayed excellent stability, retaining 83% activity after five cycles, as confirmed by structural characterizations. In substrate scope studies, various aryl halides and indole derivatives were successfully transformed, with electron-withdrawing groups generally giving higher yields (up to 88%) compared with electron-donating substituents. The position of substituents on indole also influenced yields, with steric hindrance lowering the efficiency. Overall, this work demonstrates that Cu-BDC–SO₃Na-CTAB is a stable, reusable, and highly efficient catalyst for C–S bond formation, offering yields up to 94%, excellent recyclability, and broad substrate compatibility, making it a promising material for sustainable thioether synthesis (See Figure ).

3.

Cu-BDC–SO₃Na-CTAB is a stable, reusable, and highly efficient catalyst for efficient multicomponent C–S coupling reactions.

Copper complexes of thiazolo­[5,4-d]­thiazole-based porous polymers (Cu–TTZ-POPs) are multifunctional heterogeneous catalysts. The synthesis strategy involved building porous organic polymers from thiazolo­[5,4-d]­thiazole (TTZ) ligands via a polymerization approach, followed by coordination of Cu²⁺ ions into the framework. This process yielded a highly porous, thermally stable material with a large surface area, abundant Lewis acidic Cu sites, and robust chemical durability. The porous structure ensured efficient diffusion of reactants, while the electron-rich TTZ moiety provided additional stabilization of the catalytic intermediates. Spectroscopic and microscopic analyses confirmed uniform copper distribution and the preservation of the POP’s ordered porous framework.

In catalytic applications, Cu–TTZ-POPs exhibited outstanding activity and selectivity in the synthesis of 2-arylquinolines and 2-arylbenzothiazoles, which are important heterocyclic scaffolds in pharmaceuticals and fine chemicals. For 2-arylquinolines, yields reached up to 98%, and those for 2-arylbenzothiazoles reached up to 97%, under relatively mild reaction conditions, showcasing the efficiency of the catalyst. Importantly, the heterogeneous catalyst was recyclable: after six catalytic cycles, more than 90% of the original activity was retained with negligible copper leaching, proving its stability. Compared to conventional homogeneous catalysts, Cu–TTZ-POPs offered advantages in terms of greener synthesis (reduced solvent waste and easy separation), high product yield, and excellent reusability. This work demonstrates how metal–organic porous frameworks integrated with thiazolo-thiazole ligands can serve as a sustainable platform for C–C and C–N bond-forming reactions, bridging the gap between homogeneous efficiency and heterogeneous reusability (see Figure )­F.

4.

Copper complexes of thiazolo­[5,4-d]­thiazole-based porous polymers (Cu–TTZ-POPs) for C–C and C–N bond-forming reactions.

UiO-66-NH₂-based MOFs modified with Pd and Cu via a double-solvent method. Initially, UiO-66-NH₂ was synthesized solvothermally, followed by the incorporation of Pd and Cu nanoparticles. The design strategy aimed to create synergistic bimetallic sites within the porous MOF structure, which enhances the catalytic activity for selective hydrogenation reactions. The characterization confirmed successful loading of Pd and Cu, with a uniform dispersion of metal nanoparticles inside the MOF pores.

In terms of the results, the Pd₁₀Cu₉₀@UiO-66-NH₂ catalyst showed remarkable performance in the selective hydrogenation of 5-hydroxymethylfurfural (HMF). It achieved 100% HMF conversion with 93% selectivity to 2,5-dihydroxymethylfuran (DHMF) under mild conditions (30 °C, 1 MPa H₂, 2 h). Compared with monometallic Pd@UiO-66-NH₂ (86% selectivity) and Cu@UiO-66-NH₂ (75% selectivity), the bimetallic system clearly outperformed, highlighting the strong Pd–Cu synergistic effect. Furthermore, the catalyst maintained >90% selectivity after five consecutive cycles, confirming its stability and reusability.

Copper­(I) MOF (Cu-Mel) ) was synthesized via a straightforward hydrothermal method using Cu⁺ ions and melamine as precursors, and it functions as a laccase-like nanozyme. Cu-Mel, they explored its catalytic performance in oxidizing 4-aminoantipyrine (4-AP) and 2,4-dichlorophenol (2,4-DP), under various conditions (temperature, alcohol presence, and ionic strength), including measuring its maximum reaction rate (V _max) to determine optimal laccase-like activity. The Cu-Mel nanozyme demonstrated strong catalytic performance: it exhibited a significantly elevated V _max compared to baseline or similar systems, though the exact numeric value is not disclosed in the abstract. It also provided good storage stability, retaining activity over time. Most notably, when applied to degrade the dye CR, Cu-Mel achieved notable degradation efficiency, showcasing striking practical potential in environmental remediation.

Cu-MOFs uniquely function both as a catalyst for generating nitric oxide (NO) from s-nitrosothiols (RSNOs) and as a fluorescent indicator for detecting NO in biological environments. Paramagnetic Cu²⁺ centers within the MOFs initially quench its luminescence at ∼450 nmbut when exposed to NO, the copper is reduced to diamagnetic Cu⁺, restoring the MOFs’ fluorescence. The Cu-MOFs display remarkable selectivity over other potential interferents (e.g., NO₂ ^–, H₂O₂, AA, NO₃ ^–, and ¹O₂). Furthermore, the Cu⁺ species catalyze the decomposition of biologically relevant RSNO donorssuch as GSNO, CysNO, and CysamNOliberating NO and subsequently oxidizing back to Cu²⁺, which in turn quenches the fluorescence again. This introduces a self-controlled feedback mechanism where the catalyst’s activity modulates its own optical signaling. Crucially, Cu-MOFs retain their structural integrity (as confirmed by powder XRD) even in aqueous environments, making them suitable for biological applications. Demonstrated in living cells, these MOFs successfully permitted real-time intracellular imaging of NO, offering both spatial and temporal resolutions of NO dynamics. The self-limiting nature of the fluorescence (i.e., luminescence restoration upon NO detection and subsequent quenching after catalysis) could be leveraged for spatiotemporally controlled NO release, with potential applications in cancer therapy or in-depth exploration of NO-mediated physiological and pathological processes.

The iodide/MOF signal amplification strategy can be used for highly sensitive colorimetric detection of H₂O₂, Cr₂O₇ ^2–, and H₂S. The synthesis of Cu-MOFs (HKUST-1) was carried out by reacting 1,3,5-benzenetricarboxylic acid with CuSO₄·7H₂O in a methanol–water mixture, producing blue crystalline Cu-MOF precipitates. These MOFs were then combined with iodide (KI), which could easily enter the porous Cu-MOF framework and act synergistically to enhance their catalytic activity. The iodide–Cu-MOF composite showed a dramatic improvement in peroxidase-like activity, catalyzing the oxidation of TMB (3,3′,5,5′-tetramethylbenzidine) to a blue product in the presence of target analytes. Characterizations using TEM, DLS, XRD, BET, FT-IR, and XPS confirmed iodide incorporation without structural collapse of the MOFs, with the surface area increasing from 238.7 to 844.6 m²/g after iodide loading.

The results demonstrated remarkably enhanced detection sensitivity compared to that of unamplified assays. The developed colorimetric platform achieved detection limits of 25 nM for H₂O₂, 30 nM for Cr₂O₇ ^2–, and 0.2 nM for H₂S, which are ∼200-fold lower than conventional colorimetric methods. For H₂O₂ detection, a linear response was obtained between 50 nM and 500 μM, with a molar absorption coefficient of 3.8 × 10⁶ M^–1 cm^–1. In the absence of iodide, the limit of detection worsened drastically to 10 μM, almost 2 orders of magnitude higher. For Cr₂O₇ ^2–, the iodide-MOF system achieved a detection limit of 30 nM, compared to 1 μM without iodide. For H₂S, which inhibits the catalytic activity of Cu-MOFs, the method achieved a detection range of 1 nM–0.2 μM with a limit of detection of 0.2 nM. The system also demonstrated high selectivity against interfering biomolecules and successful application in detecting H₂O₂ in real human serum samples with recoveries of ∼95–105%, proving its robustness and practical utility (See Table ).

5. Application of Cu-MOFs in Catalysis.

Cu-MOF/system	catalytic performance/data	application/significance	ref
general Cu-MOFs (BDC, BTC, etc.)	high yields (80–99%) in C–C and C–N bond formation; recyclable; minimal leaching	heterogeneous catalysis: cross-coupling, oxidation, esterification, hydroxylation, condensation	– ,
NU-1000 with Cu oxide clusters (Lercher,2017/2019)	45–60% methanol selectivity; tricopper clusters (Cu–Cu ∼2.93 Å) more active than mononuclear	methane-to-methanol conversion; nuclearity controls activity	,
MOF-808 (Baek, 2018)	dicopper sites stabilized; high methanol selectivity at 150 °C	selective methane oxidation to methanol	,
ZIF-7 (Lee, 2022)	mononuclear CuN4 sites; suppressed overoxidation; improved methanol selectivity	methane C–H bond activation with high selectivity	,
Cu–BTC (HKUST-1)	ethylbenzene conversion 44.92%, selectivity 92.53%; solvent-free; high T (150 °C, 24 h)	oxidation of ethylbenzene to acetophenone
Cu–BTC–SiO2Monolith II	>99% conversion and selectivity; requires benzonitrile solvent	ethylbenzene oxidation under milder conditions
HPW@Cu-MOFs (phosphotungstic acid composite)	∼100% SO2 removal at 200 °C; SA = 612.20 m2/g; sulfur capacity 90.46mg/g	flue-gas desulfurization (oxidation + adsorption)
Cu-BDC–SO3Na-CTAB	C–S coupling yield 94% (vs 75% Cu-BDC, 62% Cu-BTC, 80% unmodified); retains 83% activity after 5 cycles	green synthesis of thioethers using elemental sulfur
Cu–TTZ-POPs (thiazolo[5,4-d]thiazole porous polymers)	yields: 2-arylquinolines (98%), 2-arylbenzothiazoles (97%); >90% activity retained after 6 cycles	heterocyclic synthesis in pharmaceuticals and fine chemicals
Pd–Cu@UiO-66-NH2	HMF → DHMF: 100% conversion, 93% selectivity; superior to Pd-only (86%) and Cu-only (75%); stable over 5 cycles	selective hydrogenation; biomass upgrading
Cu–Mel MOFs (Cu(I) + melamine)	laccase-like nanozyme; high V max; strong Congo Red dye degradation	environmental remediation; dye and phenol degradation
Cu-MOFs for NO generation and detection	dual role: NO generation from RSNOs + fluorescence sensing; selective in biological media; reusable	biomedical: NO imaging in living cells; potential cancer therapy
iodide–Cu-MOFs (HKUST-1 + KI)	enhanced peroxidase-like activity; detection limits: H2O2 (25 nM), Cr2O7 2– (30 nM), H2S (0.2 nM); ∼200× more sensitive than conventional	biosensing and environmental monitoring of reactive species

8. Application of Cu-MOF-Based Composites in Electrocatalysis

Cu-MOFs can be used as electrocatalysts for high-efficiency electrochemical CO₂ conversion, addressing recent scientific advancements, mechanisms, material design, and practical challenges. − The drive behind such research stems from the urgent global need to mitigate carbon emissions and achieve carbon neutrality. Since CO₂ is a thermodynamically stable, linear molecule with a high bond dissociation energy (∼750 kJ/mol), efficiently reducing and upgrading this greenhouse gas into valuable chemicals requires advanced catalyst systemsespecially those capable of overcoming the kinetic and thermodynamic limitations associated with multielectron, multiproton transfer processes. MOFs, including those based on copper, offer immense design flexibility due to their modular assembly from metal nodes and organic linkers. Their high surface area and porous architecture foster efficient CO₂ capture and mass transfer, exposing numerous well-defined and tunable catalytic sites. The organic linker and the arrangement of the metal clusters can be systematically selected and modified to optimize the electronic environment and pore structure, which directly influence catalyst reactivity, selectivity, and resistance to undesired competing processes like the HER. MOFs can also be further engineered through defect creation, ligand functionalization, and nanostructuring to expose more active sites and enhance charge mobility.

The electrochemical reduction of CO₂ (CO₂RR) on Cu-MOFs can yield a broad spectrum of products, ranging from C1 compounds (e.g., CO, CH₄, and HCOOH) to C₂ compounds (e.g., C₂H₄, CH₃COOH, and C₂H₅OH). Product selectivity hinges on modulating the binding energies of key intermediates such as *COOH and *CO, as well as stabilizing crucial transition states. For instance, copper uniquely balances adsorption energies: it is able to bind the CO intermediate moderately, which is essential for hydrocarbon formation, while avoiding strong H binding that would otherwise lead predominantly to hydrogen production by HER. The detailed DFT studies cited in the review further elucidate that the nature of the ligand, defect structure, and presence of hydrogen-bonding networks (from functional groups like hydroxyls) direct the pathway toward the desired products by stabilizing specific intermediates or lowering activation energies. A variety of synthesis strategiesincluding hydrothermal, solvothermal, chemical precipitation, in situ electrosynthesis, and postsynthetic modificationsallow for precise tailoring of Cu-MOFs’ morphology, nanoparticle size, and nature of active sites. For example, dendritic Cu structures derived from hollow MOF precursors loaded onto layered electrodes show high current densities and elite selectivity for formate production. Similarly, engineering defects or manipulating the coordination environment, as with the introduction of SO₄ ^2– anions or N-functional groups, can enhance both the density of accessible Cu­(II) sites and the overall redox kinetics, promoting higher faradaic efficiencies and tailored product formation. Surface modification and encapsulation with other metals (bimetallic systems, such as Cu/Bi or Ag/Cu composites) further provide routes to modulate activity and suppress unwanted pathways.

Cu-MOFs can reach Faradaic efficiencies (FE) as high as 98.2% for formic acid, 73% for methane, and around 50% for ethylene in optimized systems. Notably, the porous structure and controlled nanostructuring allow high current densities (such as 102.1 mA/cm² achieved for formate on dendritic Cu-MOFs). Derivatives of Cu-MOFs, such as those containing Cu₂O quantum dots or tailored to expose (111) or (100) facets, display remarkable ability to direct multicarbon product formationparticularly ethylene and ethanolthanks to their impact on the C–C coupling step, which remains a kinetic bottleneck in the CO₂RR. The design of the electrochemical reactor plays a pivotal role in both the scientific study and potential industrial application of CO₂RR. H-type cells are valuable for mechanistic work and initial catalyst screening, but their limitations (mainly low current density due to gas–liquid mass transfer constraints) make them suboptimal for scale-up. Flow reactors with gas diffusion electrodes (GDEs) break through solubility bottlenecks, enabling higher current densities and efficient three-phase boundary formation, which is essential for commercial viability. High-temperature solid oxide electrolytic cells go further, allowing for the direct conversion of CO₂ and H₂O into methane and other gases by leveraging a higher thermal energy and unique ionic conduction mechanisms.

Despite the remarkable advances, several significant challenges persist. Improving C₂+ product selectivity (e.g., ethylene or ethanol) remains difficult due to the high kinetic barrier of C–C coupling and the competition with parallel reduction or hydrogenation pathways. Catalyst conductivity and stabilityoften hindered by the dynamic restructuring of MOF frameworks under electrochemical conditionsmust be consistently managed if these materials are to persist under real-world operating regimes. Understanding the postelectrolysis evolution of active Cu sites and the fate of organic linkers during sustained operation remains a key research gap, calling for advanced in situ and operando techniques such as XAS, Raman, and FTIR spectroscopy. Looking forward, the intersection of machine learning and artificial intelligence with high-throughput DFT calculations and advanced experimental observables is poised to rapidly accelerate the discovery and optimization of MOFs-based electrocatalysts. Such digital approaches can unearth hidden structure–property–performance correlations, predict transition states, and pinpoint optimal synthetic conditions for multiactive-site catalysts. Further, multiscale modeling can guide the development of new reactor architectures and process-intensification strategies, such as expanded three-phase interfaces or novel GDE functionalization techniques, to match the performance of the most promising Cu-MOF electrocatalysts.

Overall, Cu-based MOFs provide a modular, tunable platform for addressing the complex challenge of CO₂ electroreduction. By integrating advances in material synthesis, mechanistic understanding, reactor design, and data-driven optimization, the field is moving closer toward practical, scalable solutions for sustainable carbon management and chemical manufacturing.

Atomically dispersed, heteroatom-doped copper–catecholate MOF nanoarrays (Cu-CAT) were directly deposited on copper foam (CF) for bifunctional electrocatalysis: hydrogen evolution (HER) and selective glycerol oxidation (GOR). The synthesis grows Cu-CAT on preformed Cu­(OH)₂ nanoneedles via a short solvothermal ligand-exchange with HHTP (water/DMF = 10:1) at 70 °C for 10 min; doping is achieved simply by adding metal salts (e.g., RuCl₃, IrCl₃, PdCl₂, CoCl₂·6H₂O, NiCl₂·6H₂O, ZnCl₂) to yield M-doped Cu-CAT/CF in one step. Density functional theory shows that introducing these heterometals downshifts the MOF d-band center, optimizing H adsorption/water activation and identifying electron-rich dopant sites as the true active centers for both HER and GOR. Numerically, Ru-doped Cu-CAT delivers standout HER metrics: η₁₀ = 18 mV and η₁₀₀ = 55 mV versus Cu-CAT (88 mV, 180 mV) and even Pt/C (37 mV, 135 mV); Tafel slopes for doped MOFs are 43.2–66.6 mV dec^–1 (vs 102.2 mV dec^–1 for undoped), exchange current densities rise to 0.08–0.36 mA cm^–2 (vs 0.02), and charge-transfer resistance drops to 1.9–4.2 Ω cm² (vs 6.5). Stability holds after 1000 CV cycles and 20 h operation. For the anode, RuCu-CAT lowers the 10 mA cm^–2 requirement from 1.56 V (OER) to 1.23 V in 0.5 M glycerol; at 20–200 mA cm^–2, GOR remains ≥210 mV easier than OER, with a GOR Tafel slope of 85.8 mV dec^–1 (vs 162.2 mV dec^–1 for OER). In full cells using RuCu-CAT/CF at both electrodes, the HER//GOR hybrid electrolyzer reaches 10 mA cm^–2 at 1.36 V (vs 1.70 V for HER//OER), gives ∼100% H₂ Faradaic efficiency, and at 1.40 V sustains 85 mA cm^–2 with ∼90% formate FE from glycerol; operation is stable for 20 h. Together, these data show that dopant-tuned Cu-CATs enable energy-saving H₂ production coupled to value-added formate synthesis.

The copper centers in Cu-MOF catalysts influence their performance in the electrocatalytic hydrodimerization of acetylene into 1,3-butadiene. The researchers synthesized a family of Cu-MOF electrocatalysts featuring well-defined nuclearities: mononuclear (Cu₁-MOFs), dinuclear (Cu₂-MOFs), and a trinuclear MOF ([Cu₃(μ₃–OH)­(μ₃-trz)₃(OH)₂(H₂O)₄]·xH₂O, referred to as Cu₃-MOFs). Advanced operando techniques, including electrochemical Raman and FT-IR spectroscopyalongside theoretical simulations, revealed that single Cu sites predominantly promote semihydrogenation to ethylene, whereas neighboring dual Cu sites, as present in the Cu₃-MOFs, facilitate both adsorption of acetylene and efficient C–C coupling of the *C₂H₂ and *C₂H₃ intermediates toward forming 1,3-butadiene. The standout performer, Cu₃-MOFs, exhibited remarkable activity: a high 1,3-butadiene selectivity of 91% and a production rate of 64 mmol g^–1 h^–1. These metrics represent approximately a 2-fold increase in selectivity and a 20-fold increase in production rate compared with Cu₂-MOFs and Cu₁-MOFs, respectively. Overall, this work provides deep mechanistic insight into how precise engineering of active-site nuclearity within MOFs can drastically enhance electrocatalytic C–C coupling efficiency, offering a rational design strategy for high-performance, sustainable catalytic systems for 1,3-butadiene synthesis.

Defect-engineered Cu-MOFs were constructed by carefully designing the coordination environment around copper centers. The parent Cu-MOFs were built using copper nodes and organic linkers (typically polycarboxylate or polyhydroxy aromatic ligands) under solvothermal conditions. To create defects, they employed a ligand modulation strategy: during the synthesis, they deliberately reduced the ratio of the organic linker relative to Cu²⁺ ions. This meant that not all copper sites were fully coordinated by linkers, leaving some sites undercoordinated (open metal sites). These unsaturated copper centers acted as defects within the MOF structure.

The introduction of these coordination defects altered the electronic structure of the Cu sites and generated dual active environments: (i) Cu–O sites, which strongly adsorbed CO₂ molecules, and (ii) Cu–Cu species, which facilitated C–C coupling. This defect engineering improved the binding and stabilization of key intermediates such as *CO and lowered the energy barrier for *CO dimerization. As a result, the defective Cu-MOFs showed much higher selectivity for C₂ ⁺ products (ethylene, ethanol, etc.) compared to the pristine defect-free Cu-MOFs. Electrochemical performance tests demonstrated that the defect-engineered Cu-MOF catalyst achieved a Faradaic efficiency (FE) of 68.4% for C₂ ⁺ products at −1.05 V vs RHE, with an overall current density of 204 mA cm^–2 in the flow-cell configuration. The catalyst showed particularly high selectivity toward ethylene with an FE of 43.7% and toward ethanol with an FE of 21.3%, significantly outperforming pristine Cu-MOFs (C₂ ⁺ FE < 40%). Durability tests revealed stable performance for over 40 h with negligible loss in efficiency. DFT calculations further revealed that defect-rich Cu sites reduced the energy barrier for *CO dimerization, a critical step for C–C coupling, thus promoting the formation of C₂ ⁺ products.

Dual-ligand copper-based MOFs enhance the electrocatalytic reduction of nitrate (NO₃ ^–) to ammonia (NH₃). The Cu-MOFs were constructed by incorporating two different organic linkers: 1,3,5-benzenetricarboxylate (BTC) and 1,4-benzenedicarboxylate (BDC). This dual-ligand approach allowed fine-tuning of the coordination microenvironment around Cu sites, improving both stability and electronic conductivity compared to single-ligand Cu-MOFs. The synthesis was performed via a solvothermal route, resulting in highly crystalline structures with uniform particle size and well-defined porosity, which facilitated ion transport and enhanced the accessibility of active Cu centers. Structural characterization confirmed the successful incorporation of both ligands and the preservation of the MOF framework integrity.

Electrocatalytic tests demonstrated that the dual-ligand Cu-MOFs exhibited significantly higher performance compared with single-ligand MOFs. At an applied potential of −0.6 V vs RHE, the optimized Cu-MOFs achieved a Faradaic efficiency (FE) of 91.7% for NH₃ production with a corresponding yield rate of 1265.9 μg h^–1 mg^–1_cat. In contrast, single-ligand Cu-BTC and Cu-BDC showed FE values below 70%. Moreover, the dual-ligand Cu-MOFs retained their activity for over 20 h of continuous electrolysis with minimal loss in efficiency, demonstrating excellent durability. Kinetic studies revealed first-order reaction dependence with an apparent rate constant of 0.263 min^–1, further validating the improved reaction kinetics introduced by the dual-ligand coordination environment.

Bimetallic MOFs using nickel (Ni) and copper (Cu) ions were combined with 1,4-benzene dicarboxylic acid (BDC) as the organic linker through a solvothermal approach. In the synthesis, Ni and Cu salts were mixed in a 2:1 ratio, dissolved in N,N-dimethylformamide (DMF), and combined with BDC before adding sodium hydroxide (NaOH); the mixture was then heated at 120 °C for 16 h and cured at 150 °C. Structural characterization confirmed the successful formation of a crystalline, thermally stable (up to 378 °C) product with a surface area of 122.14 m²/g and average pore size of 3.07 nm, which exceeded the values for monometallic MOFs. Elemental analysis and imaging confirmed the uniform distribution of Ni and Cu at the nanoscale, with particle sizes averaging around 50 nm.

Electrochemical measurements highlighted the superior OER activity of the Ni–Cu MOFs in an alkaline 1 M KOH electrolyte. The material showed a low overpotential of 340 mV at a current density of 10 mA/cm² and a Tafel slope of 65 mV/decade, both figures outperforming those of individual Ni-MOFs (overpotential: 440 mV, Tafel slope: 158.5 mV/dec) and Cu-MOFs (overpotential: 640 mV, Tafel slope: 113.9 mV/dec). The charge transfer resistance, measured at 15.2 Ω/cm², was also much lower for the bimetallic MOFs, indicating higher conductivity and improved electron transfer. Turnover frequency (TOF) reached 16.20 s^–1 at 1.64 V versus RHE, and mass activity was calculated as 83.9 A/g at 1.61 V. The MOFs demonstrated stable catalytic performance during extended operation (up to 7200 s) with negligible changes in current density and potential, positioning it as an efficient and durable catalyst for water-splitting and renewable energy applications (see Table ).

6. Applications of Cu-MOFs in Electrocatalysis.

system/strategy	material design and features	mechanism/key insight	performance metrics	applications	ref
Cu-MOFs for CO2RR (general)	modular MOFs with tunable Cu sites, high porosity, defect engineering, ligand functionalization	moderate *CO binding enables C–C coupling; linker/defect structure stabilizes intermediates (*COOH, *CO)	FE: 98.2% (HCOOH), 73% (CH4), ∼50% (C2H4); current density up to 102.1mA cm–2 (formate)	conversion of CO2 to liquid fuels (formate, ethanol) and olefins (ethylene) for green chemicals and energy storage	–
Cu-CAT nanoarrays on Cu foam (Cu-CAT/CF, heteroatom doped)	atomically dispersed Cu–catecholate MOFs, doped with Ru, Ir, Pd, Co, Ni, Zn; grown on Cu foam nanoneedles	doping downshifts d-band center, improves H adsorption and electron transfer; dopant = active center	Ru-doped: η = 18 mV, η = 55 mV, outperforming Pt/C; Tafel: 43.2–66.6 mV dec–1; HER//GOR cell: 1.36 V @ 10mA cm–2 with ∼100% H2FE and ∼90% formate FE	hybrid electrolyzers for energy-saving H2 production coupled with value-added glycerol-to-formate conversion
Cu-MOFs nuclearity control (Cu1, Cu2, Cu3-MOFs)	well-defined single, di-, and trinuclear Cu sites	single Cu → semihydrogenation; trinuclear Cu3 → synergistic C–C coupling of *C2H2/*C2H3	Cu3-MOFs: 91% selectivity for 1,3-butadiene, production rate 64 mmol g–1 h–1 (≈2× selectivity, 20× rate vs Cu2, Cu1)	electrocatalytic acetylene valorization to 1,3-butadiene (key monomer for synthetic rubber and polymers)
defect-engineered Cu-MOFs	ligand modulation to create under-coordinated Cu sites (Cu–O + Cu–Cu)	dual sites enhance CO2 adsorption and lower barrier for *CO dimerization → more C2 +	FE: 68.4% (C2 +products) at −1.05 V; Current density 204mA cm–2 (flow cell); 43.7% C2H4FE, 21.3% C2H5OH FE; stable >40 h	CO2-to-C2 + fuels (ethylene, ethanol) in flow reactors for scalable carbon-neutral fuels
dual-ligand Cu-MOFs (BTC + BDC)	solvothermal synthesis; dual ligands improve conductivity and stability	tuned coordination enhances NO3 – → NH3 conversion	FE(NH3) 91.7%; yield rate 1265.9 μg h–1mg–1_cat at −0.6 V; stable >20 h	green ammonia synthesis for fertilizers and hydrogen carriers (alternative to Haber–Bosch)
bimetallic Ni–Cu MOF (BDC linker)	Ni/Cu = 2:1 ratio, solvothermal; high surface area (122.1 m2/g), pore size 3.07 nm	synergistic Ni–Cu centers improve OER kinetics, conductivity	OER: η(10 mA/cm2) 340 mV, Tafel slope 65 mV/dec; TOF 16.2 s–1; mass activity 83.9A g–1; stable 7200 s	water-splitting/OER catalysts for renewable H2 production in alkaline electrolyzers

9. Application of Cu-MOF-Based Composites in Photocatalysis

In photocatalysis, Cu-MOFs have been successfully applied to the degradation of organic dyes, the reduction of toxic metal ions, and the CO₂ photoreduction. Their ability to absorb visible light and facilitate charge separation is further improved through morphology engineering, as in the case of rod-shaped Cu-MOFs with carboxylate double linkers, which demonstrated efficient Cr­(VI) reduction and rhodamine B degradation under sunlight. In electrocatalytic CO₂ reduction, Cu-MOFs serve as active components or supports in tandem systems to produce multicarbon (C₂ ⁺) products with higher energy density. − Cu-MOFs have also been explored for catalytic ozonation in water treatment, where their large surface areas and redox-active centers accelerate the decomposition of ozone into reactive species.

Hydrothermally synthesized Cu-MOFs loaded with phosphotungstic acid (HPW) prepared by mixing Cu­(NO₃)₂ and 1,3,5-H₃BTC were used in a 2:1 ratio, with HPW introduced at varying loadings (0.6–1.8 wt %) was used for dry desulfurization of SO₂. The optimum material, HPW-2@Cu-MOF (1.2 wt % HPW, 24 h synthesis), achieved nearly 100% SO₂ removal efficiency at 200 °C in a fixed-bed reactor, with a sulfur capacity of 90.46 mg/g, a surface area of 612.20 m²/g, and a pore volume of 0.2568 cm³/g. XPS analysis confirmed that W⁵⁺ species (90.6%) acted as the active catalytic centers, while lattice and surface oxygen (Oβ, Oα) promoted SO₂ oxidation to SO₃, which increased by 10.52% compared with bare Cu-MOFs. Thermal stability was also improved, with HPW preventing framework collapse at elevated temperatures.

Key performance results show that SO₂ removal remained effective even under CO₂-rich conditions, where HPW-2@Cu-MOFs maintained a sulfur capacity of 60.38 mg/g with 41 min of 100% desulfurization efficiency. Recycling tests demonstrated strong durability: after four cycles, the desulfurization efficiency remained 76.4%, with W⁵⁺ still accounting for 40.56%. SEM revealed octahedral morphology, while XRD confirmed successful HPW encapsulation without destroying the Cu-MOF structure. These results demonstrate that coupling HPW’s catalytic activity with Cu-MOF adsorption capacity provides a synergistic pathway for ultralow SO₂ emissions, surpassing traditional Ca-based and oxide sorbents in both efficiency and reusability.

The Cu-MOFs and their conversion into CuO _x –C@CCDC composites for enhanced catalytic performance in peroxymonosulfate (PMS) activation. The Cu-MOFs were prepared via a hydrothermal method, where cotton-derived carbon served as the carbon source and template. Upon calcination, the MOFs transformed into a CuO _x –C composite embedded in cotton-derived carbon (CCDC), ensuring a high surface area, abundant active sites, and improved conductivity. This structural integration leveraged the hierarchical porosity and uniform dispersion of Cu species, which are crucial for efficient electron transfer and PMS activation. The integration of MOF-derived copper species with cotton-derived carbon (CCDC) generated a hierarchical porous material containing metallic Cu, CuO, and graphitic carbon. This architecture enhanced surface area (BET ≈ 441.9 m²/g), defect density, and electrical conductivity, all of which facilitated efficient PMS activation. Figures confirmed the fibrous morphology (SEM/TEM), crystalline phases of Cu and CuO (XRD), surface defects (Raman), and coexistence of Cu(0)/Cu­(II) with nitrogen functionalities (XPS), collectively verifying the successful synthesis.

Catalytic performance evaluations demonstrated that CuO _x –C@CCDC/PMS degraded 97% of sulfoxazole (SIZ) within 20 min, which was 6.47 and 10.44 times faster than those of CuO _x –C and CCDC alone. Figures also showed robustness across a wide pH range (3–11), strong resistance against inorganic anions (Cl^–, NO₃ ^–, SO₄ ^2–, and HCO₃ ^–), and high selectivity toward electron-rich pollutants like sulfamethoxazole, ciprofloxacin, tetracycline, and meropenem (>90% removal). Radical quenching and electron paramagnetic resonance (EPR) tests revealed a pathway transformation from radical (^•OH, SO₄ ^•–) to nonradical electron-transfer mediated oxidation, which minimized interference and enhanced stability. Long-term experiments confirmed >88% efficiency after 600 min continuous flow operation, with stable recyclability over five cycles and low Cu leaching (<EU and US limits). These outcomes demonstrate the material’s promise as a scalable PMS activator for practical wastewater treatment.

The solvothermal synthesis and photocatalytic applications of two coordination polymers: Cu-based MOFs {[Cu₃(tib)₄(NO₃)₄(H₂O)]·2NO₃·2.96H₂O}_n(complex 1) and Ni-based MOF {[Ni­(tib)₂]·2NO₃} _n (complex 2), both formed using the tripodal ligand 1,3,5-tris­(imidazole-1-ylmethyl)­benzene (TIB). Single-crystal XRD confirmed their 3D (Cu-MOFs) and 2D brick-like (Ni-MOF) network structures, demonstrating stability, porosity, and semiconductor-like optical properties. The band gaps were calculated as 3.19 eV for complex 1 and 2.88 eV for complex 2, both suitable for visible-light photocatalysis. The BET surface areas were 5.49 m² g^–1 (Cu-MOF) and 8.54 m² g^–1 (Ni-MOF).

Photocatalytic tests showed excellent activity in tetracycline (TC) degradation and hydrogen evolution under visible light. At pH 11, complex 1 degraded 93.21% of TC within 60 min, while complex 2 achieved 91.36%, both outperforming many reported photocatalysts. Kinetic studies revealed higher pseudo-first-order rate constants (k ₁ = 0.2117 min^–1 for complex 1; 0.0807 min^–1 for complex 2). For photocatalytic hydrogen generation with a Pt cocatalyst, complex 2 achieved a remarkable rate of 681.66 μmol g^–1 h^–1, while complex 1 reached 587.39 μmol g^–1 h^–1. Mechanistic studies identified superoxide radicals (·O₂ ^–) as the main active species in TC degradation. Both MOFs maintained structural stability and photocatalytic performance after multiple cycles, demonstrating their promise for environmental remediation and clean energy production.

The solvothermal synthesis of Cu-MOFs using copper nitrate and organic linkers yielded a crystalline porous framework with high stability and strong visible-light absorption. Characterization confirmed the structural integrity, porosity, and optical activity of the material, with a measured band gap of ∼2.4 eV and thermal stability up to ∼300 °C. These properties make the Cu-MOFs suitable as semiconductor photocatalysts under visible light. Photocatalytic tests demonstrated that the Cu-MOFs act as an efficient standalone catalyst for the arylation of phenols with diazonium salts under visible light at room temperature. The system achieved high yields up to 92–95% within 60–90 min across a broad substrate scope, with most reactions exceeding 80% yield. The catalyst also showed excellent recyclability, retaining its activity over at least five cycles with only a minor decrease in performance. Photocurrent studies confirmed strong charge separation, and mechanistic experiments identified superoxide radicals (^•O₂ ^–) and holes (h⁺) as key reactive species. These results underline the dual role of Cu-MOFs as both light harvesters and catalytic centers, offering a sustainable, reusable, and efficient pathway for C–O cross-coupling at ambient conditions.

Hierarchically structured Cu-MOFs nanowire-coated copper mesh (MCM) membranes for dual environmental applications: oil–water separation and electrocatalytic antibiotic degradation. The synthesis involved a two-step process: first, in situ growth of Cu­(OH)₂ nanowires on copper mesh via wet oxidation, followed by their conversion into Cu₃(HHTP)₂ MOF nanowires using 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as the ligand. Reaction temperature strongly influenced the morphology, with the optimal membrane (MCM3) obtained at 90 °C, displaying a coral-like nanowire structure, high surface area, and strong interfacial bonding. This architecture provided superhydrophilicity and underwater superoleophobicity, essential for efficient oil–water separation.

Performance tests demonstrated that MCM₃ achieved a water flux of 8.93 × 10³ L m^–2 h^–1 and 99.6% separation efficiency for n-hexane/water mixtures, and 2.52 × 10³ L m^–2 h^–1 with 99.3% efficiency for emulsions, sustaining >99.6% efficiency across 20 cycles. Beyond separation, the membranes served as effective electrocatalysts in PMS-assisted advanced oxidation processes, degrading 99.3% tetracycline within 20 min at 2.5 mA cm^–2, and maintaining >92% efficiency for higher concentrations and >80% for other antibiotics like levofloxacin and sulfamethoxazole. Mechanistic studies confirmed that ^•OH and ^•O₂ ^– radicals were the dominant reactive species. Thus, these bifunctional membranes integrate membrane separation with electrocatalysis, offering a scalable and robust solution for treating oily wastewater and antibiotic-contaminated effluents.

Cu-based MOFs/TiO₂ composite nanomaterials are efficient photocatalysts for hydrogen generation under visible light. The synthesis followed a straightforward route: first, a copper-based MOF was prepared via a solvothermal method using Cu²⁺ ions and organic ligands to form a porous crystalline structure with a high surface area. These MOFs were then combined with TiO₂ nanoparticles to form a composite heterojunction, ensuring intimate interfacial contact between the two phases. The rationale was that TiO₂ provides excellent stability but has a wide band gap, while the Cu-MOFs offer strong visible-light absorption and electron-donating ability. Together, the composite enhances charge separation, extends light absorption into the visible range, and accelerates surface redox reactions, crucial for photocatalytic hydrogen production.

Key results demonstrated that the Cu-MOFs/TiO₂ composites significantly outperformed pure TiO₂ and pristine MOFs. The optimal sample exhibited a hydrogen evolution rate exceeding 2500 μmol h^–1 g^–1, nearly 6–8 times higher than TiO₂ alone. This enhancement was attributed to the synergistic heterojunction, where photoexcited electrons from the Cu-MOFs efficiently transferred to TiO₂, reducing recombination losses and driving the reduction of protons to H₂. Stability tests confirmed consistent activity over multiple cycles, and mechanistic studies (PL, EIS, and photocurrent response) confirmed efficient charge transfer and separation at the MOF–TiO₂ interface. Overall, the study highlights a simple and scalable synthesis of Cu-MOF/TiO₂ nanocomposites with excellent photocatalytic efficiency, offering a promising pathway for sustainable hydrogen generation using solar energy.

A two-dimensional Fe–Cu-MOF–NH₂ material is an efficient photocatalyst for the reduction of toxic hexavalent chromium (Cr­(VI)) in water. The synthesis was carried out by a solvothermal method, where Fe³⁺ and Cu²⁺ metal precursors were coordinated with 2-aminoterephthalic acid (NH₂–BDC) as the organic linker in a DMF solvent system under controlled heating. This strategy enabled the integration of Fe and Cu centers into a layered MOF structure with exposed active sites, high crystallinity, and strong visible-light absorption. The introduction of the −NH₂ group improved electronic interactions and enhanced the light-harvesting ability, while the synergistic effect of Fe and Cu ions promoted efficient electron transfer during photocatalysis.

In terms of performance, the Fe–Cu-MOFs–NH₂ demonstrated remarkable photocatalytic efficiency, reducing nearly 100% of Cr­(VI) within 40 min under visible-light irradiation, significantly outperforming single-metal MOFs (Fe-MOFs or Cu-MOFs). The enhanced activity was attributed to the synergistic coupling of Fe and Cu centers, which facilitated charge separation, suppressed recombination, and generated reactive intermediates capable of reducing Cr­(VI) to the less toxic Cr­(III). Furthermore, the material showed excellent stability and reusability over multiple cycles with minimal loss of activity, confirming its robustness for practical wastewater treatment.

A copper-based coordination polymer catalyst constructed from copper salts and organic ligands was obtained through a hydrothermal method. It demonstrated strong degradation performance toward tetracycline antibiotics, with the optimized system achieving over 90% removal efficiency within 60 min. Kinetic studies revealed a pseudo-first-order rate constant significantly higher than that of conventional copper salts, indicating the superior activity of the MOF-like structure. Furthermore, the material exhibited excellent reusability, maintaining over 80% efficiency after 5 catalytic cycles, and stability tests confirmed minimal copper ion leaching, highlighting its environmental compatibility and durability.

A Z-scheme heterostructure photocatalyst is formed by anchoring bismuth (Bi) nanoparticles onto a composite of Bi₂MoO₆ and a Cu-MOFs. This architecture was achieved through a one-pot solvothermal process in which dimethylformamide (DMF) played a key rolecoordinating with Bi³⁺ ions and modulating their release rate to fine-tune the formation of Bi₂MoO₆ during growth. The resulting Cu-MOFs@Bi₂MoO₆ system incorporates Bi nanoparticles and engineered oxygen vacancies, forming an integrated Z-scheme heterojunction with improved charge separation and enhanced light-harvesting abilities. This heterostructure exhibited a remarkably high photocatalytic rate constant of 0.0382 min^–1 for the degradation of antibiotic ciprofloxacin (CIP). This performance surpassed that of pristine Bi₂MoO₆ by 11.93 times and exceeded that of the standalone Cu-MOFs by 18.19 times, underscoring a significant synergistic enhancement. The improvement is attributed to the surface plasmon resonance (SPR) effects from Bi nanoparticles, which, alongside oxygen vacancies, boost photoinduced charge transfer and suppress electron–hole recombination. The Z-scheme band alignment, together with an integrated electric field, drives efficient photocatalytic reaction processes. Moreover, the authors investigated degradation pathways using computational (Fukui function analysis) and experimental (LC–MS) tools, demonstrating the mechanistic depth of their study.

Upcycling electroplating sludge (ES), which is rich in Cu and minor Ni, is used to produce functional nanoflower-structured copper MOFs using a solvothermal method. Two types of MOFs were synthesized: ES-MOFs-BDC (using 1,4-benzenedicarboxylic acid) and ES-MOF-BTC (using benzene-1,3,5-tricarboxylic acid) were used as organic linkers. After drying and calcination of the sludge, the extracted metal ions were coordinated with the linkers under hydrothermal conditions (BDC system at 140 °C for 24 h; BTC system at 120 °C for 12 h). Characterization confirmed that both MOFs adopted a hierarchical nanoflower morphology, with ES-MOF-BTC showing a denser, more crystalline structure (BET surface area 316.5 m²/g) compared to ES-MOF-BDC (106.0 m²/g) and raw ES (83.4 m²/g). Importantly, ICP–MS analysis showed that the Cu content in the MOFs was enriched to over 93%, indicating preferential incorporation of Cu over Ni into the frameworks, which stabilized the structure and improved catalytic activity. Catalytic tests demonstrated that in the presence of H₂O₂, ES-MOF-BTC achieved outstanding performance in Fenton-like dye degradation: 95.76% CR removal within 60 min using only 1 mg catalyst and 10 μL H₂O₂. It also enabled complete degradation of methylene blue and ∼91% removal of Eriochrome Black T in the same time frame. Kinetic analysis revealed pseudo-first-order behavior, with ES-MOF-BTC showing a higher rate constant (k = 0.0963 min^–1) and lower activation energy (24.25 kJ/mol) compared to that of ES-MOF-BDC (k = 0.0683 min^–1, E _a = 33.25 kJ/mol). The turnover frequency (TOF) of ES-MOF-BTC reached 0.0256 min^–1, over 2× higher than ES-MOF-BDC (0.0119 min^–1). Moreover, the catalyst retained over 85% efficiency after 10 reuse cycles, and remained effective in natural water and saline conditions (NaCl up to 30 mM), confirming robustness for real wastewater applications.

Bimetallic cobalt–copper MOF (Co–Cu MOFs) anchored on amino-functionalized cellulose (NH₂-cellulose) for the efficient degradation of antibiotics in water. The MOF was prepared by solvothermal synthesis using cobalt and copper nitrates as metal precursors and terephthalic acid as the organic linker, followed by immobilization onto NH₂-cellulose. The functionalized cellulose acted as a stable support, improving dispersion, preventing MOF agglomeration, and enhancing the catalytic activity and recyclability. Structural characterizations confirmed the successful anchoring of Co–Cu MOFs on the cellulose surface with high porosity and stability suitable for catalytic applications. The catalytic performance was investigated for the degradation of tetracycline hydrochloride (TCH) in the presence of peroxymonosulfate (PMS). The Co–Cu MOF@NH₂-cellulose catalyst achieved a 94.6% TCH degradation within 30 min, which was significantly higher than that of monometallic MOFs (Co-MOF: 68.5%, Cu-MOF: 53.2%) and bare NH₂-cellulose (20.7%). The synergistic effect of cobalt and copper enhanced PMS activation by facilitating electron transfer and generating both sulfate and hydroxyl radicals. The catalyst also exhibited good recyclability, retaining 85.3% efficiency after five cycles, with negligible structural damage confirmed by XRD and FT-IR. Additionally, the degradation mechanism involved reactive oxygen species (ROS) such as SO₄ ^•–, ^•OH, and singlet oxygen (¹O₂), with EPR analysis supporting their presence.

Urchin-like Cu _x Ce_1–x O _y -BTC catalysts were derived from a MOF precursor for the catalytic ozonation of phenol. The synthesis process involved preparing Cu–Ce–BTC MOFs via a solvothermal route, followed by calcination to obtain mixed metal oxides with a unique urchin-like morphology. The MOF precursor played a crucial role in generating highly dispersed Cu and Ce species, abundant oxygen vacancies, and a hierarchical porous structure that facilitates ozone activation. Structural characterizations confirmed a uniform dispersion of Cu and Ce oxides, high surface area, and abundant oxygen vacancies, which are central to the catalytic mechanism. The catalysts showed excellent performance in phenol degradation. Among the series, Cu₀.₅Ce₀.₅O _y -BTC demonstrated the best activity, achieving 99% phenol removal and 92% total organic carbon mineralization within 60 min. This performance surpassed that of pure CuO or CeO₂ catalysts, highlighting the synergy between Cu and Ce in generating ROS. Electron spin resonance and quenching experiments confirmed that ^•OH and ^•O₂ ^– radicals were the dominant active species, while XPS revealed cycling between Ce³⁺/Ce⁴⁺ and Cu⁺/Cu²⁺, which promoted ozone decomposition and electron transfer. The material also showed good stability, maintaining over 90% phenol removal efficiency after five consecutive cycles.

Ultrathin MOF molecular layers (MOLs) serve as a catalytic platform for the CO₂ photoreduction. The synthesis began with the preparation of Ni-MOL, which was chosen as an inert base material. Through controlled substitution, a fraction of Ni sites was replaced with Cu, yielding Cu–O–Ni heterojunctions. This doping preserved the ultrathin lamellar morphology (∼2.2 nm thick, two molecular layers) but altered the local electronic environments: Cu acted as a light-harvesting site while Ni provided electron localization and CO₂ adsorption capacity. Subsequently, Pd nanoparticles (∼5 nm) were uniformly immobilized on the Cu₂Ni-MOL surface. The ultrathin 2D structure of MOLs ensured abundant accessible active sites and efficient mass and electron transport, while Pd imparted localized surface plasmon resonance (LSPR) effects to amplify the local electromagnetic field. Photocatalytic performance tests under simulated sunlight confirmed the synergy of this design. Monometallic Ni-MOL and Cu-MOL showed poor activity (3.36 and 6.18 μmol/g CO in 4 h), while Cu₂Ni-MOL achieved 65.75 μmol/g CO due to the cooperative action of Cu–O–Ni sites. With optimized Pd loading, Pd1.5@Cu₂Ni-MOL reached 194.74 μmol/g of CO, with nearly 100% CO selectivitya 58-fold and 29-fold enhancement over Ni-MOL and Cu-MOL, respectively. The catalyst displayed broad light absorption up to 765 nm and the highest quantum efficiency of 0.302% at 365 nm.

Mechanistic studies using in situ FTIR, XPS, and DFT calculations showed that Cu generates electron-rich sites, while Ni is electron-deficient, forming a polarization-driven directional electric field. Electrons flow from Cu to Ni, where CO₂ is adsorbed and activated to *COOH (adsorption energy −0.73 eV). Meanwhile, Pd LSPR “hot spots” accelerated carrier transfer, further boosting the activity. Overall, the rational MOF synthesis combining Cu–Ni bimetallic heterojunctions with plasmonic Pd NPs provides a powerful route for efficient and selective CO₂ photoreduction.

A series of Cu-MOFs were constructed using a bifunctional 4-pyridine-hydroxamate (4-PyHA) ligand, leading to three distinct frameworks: SUM-23A, SUM-23B, and SUM-33. These MOFs were prepared under solvothermal conditions, where the choice of solvent and additives dictated the crystal formSUM-23A formed as octahedral crystals in DMF, SUM-23B emerged as a phase-transformed structure upon ethanol treatment, and SUM-33 was obtained as rod-shaped crystals when aqueous ammonia was introduced. Among these, SUM-33 demonstrated exceptional performance as a photocatalyst for CO₂ reduction to CO under simulated sunlight. Compared to SUM-23B, which produced negligible amounts of CO (∼0.02 units), SUM-33 achieved a significantly higher yield (∼3.05 units), highlighting its superior catalytic activity and selectivity. Importantly, SUM-33 maintained its structural integrity and catalytic efficiency over multiple photocatalytic cycles, proving its reusability and stability. The study establishes hydroxamate-based ligands as effective building blocks for designing robust, porous, and photochemically active MOFs, with SUM-33 offering a promising platform for sustainable CO₂ utilization technologies.

A Cu­(I)/Cu­(II)-MOF incorporated hydrogel photocatalyst was used aimed at the synergistic removal of Cr­(VI) and CR from wastewater. The Cu-MOF was synthesized through a hydrothermal method, where copper salts were coordinated with organic linkers to form the crystalline MOF structure. This MOF was then uniformly embedded into a polyacrylamide hydrogel matrix, creating a flexible and stable composite material with enhanced adsorption and photocatalytic properties. The hydrogel not only improved the dispersion of the MOF particles but also provided additional binding sites and mechanical stability, enabling effective interactions with pollutants. The Cu-MOF@hydrogel photocatalyst showed excellent synergistic removal efficiencies. Under visible light irradiation, it achieved 94.7% removal of Cr­(VI) within 60 min and 92.3% degradation of CR within 75 min. The system also demonstrated remarkable cycling stability, maintaining over 80% efficiency after 5 reuse cycles, and leaching tests confirmed minimal copper release, ensuring environmental safety. Kinetic analysis revealed pseudo-first-order rate constants significantly higher than those of pristine MOF or hydrogel alone, confirming the synergistic advantage of the composite structure. Overall, the work demonstrates a promising multifunctional photocatalyst for wastewater treatment with high activity, stability, and recyclability (See Table ).

7. Applications of Cu-MOF-Based Composites in Photocatalysis.

system/material	synthesis method	application	key performance results	mechanism/features	ref
Cu-MOFs (rod-shaped with carboxylate double linkers)	morphology engineering	Cr(VI) reduction and rhodamine B degradation	efficient degradation under sunlight	visible light absorption, improved charge separation
HPW@Cu-MOF (HPW-2, 1.2 wt %)	hydrothermal (Cu(NO3)2 + H3BTC, HPW loading)	dry desulfurization (SO2 removal)	∼100% SO2 removal at 200 °C, sulfur capacity 90.46 mg/g; 76.4% retained after 4 cycles	W5+ active centers, Oα/Oβ lattice oxygen promote SO2 oxidation; HPW prevents collapse
CuO x –C@CCDC composites (from Cu-MOF + cotton-derived carbon)	hydrothermal + calcination	PMS activation for pollutant degradation	97% sulfoxazole removal in 20 min; >88% stability after 600 min continuous flow	hierarchical porosity, Cu(0)/Cu(II), graphitic carbon → radical and nonradical pathways
Cu-MOF (complex 1) and Ni-MOF (complex 2) with TIB ligand	solvothermal	photocatalytic tetracycline degradation & H2 evolution	Cu-MOF degraded 93.21% TC in 60 min; Ni-MOF produced 681.66 μmol g–1 h–1 H2	band gaps 3.19 and 2.88 eV; •O2 – main species; high recyclability
Cu-MOF for C–O cross-coupling	solvothermal	visible-light arylation of phenols	92–95% yield within 60–90 min; stable over 5 cycles	band gap ∼2.4 eV; •O2 – and h+ species key
Cu-MOF nanowire-coated Cu mesh (MCM3)	wet oxidation + MOF growth	oil–water separation and electrocatalytic antibiotic degradation	99.6% oil/water separation; 99.3% tetracycline degradation in 20 min	coral-like nanowires, •OH & •O2 – radicals dominate
Cu-MOF/TiO2 nanocomposite	solvothermal + composite formation	photocatalytic H2 evolution	>2500 μmol h–1 g–1 H2 (6–8× TiO2); stable over cycles	synergistic heterojunction enhances visible absorption and charge separation
Fe–Cu-MOFs–NH2	solvothermal (Fe3+, Cu2+ + NH2–BDC)	Cr(VI) reduction	∼100% Cr(VI) removal in 40 min	synergistic Fe–Cu centers, −NH2 improves charge transfer
Cu-based coordination polymer	hydrothermal	tetracycline degradation	>90% degradation in 60 min; >80% efficiency after 5 cycles	MOF-like framework stability, low Cu leaching
Cu-MOF@Bi2MoO6Z-scheme heterojunction with Bi NPs	One-pot solvothermal	ciprofloxacin degradation	rate constant 0.0382 min–1(11.93× Bi2MoO6; 18.19× Cu-MOF)	Bi SPR + oxygen vacancies enhance charge separation
Cu-MOFs from electroplating sludge (ES-MOF-BDC, ES-MOF-BTC)	solvothermal (BDC/BTC ligands)	Fenton-like dye degradation	ES-MOF-BTC: 95.76% Congo Red removal in 60 min; TOF = 0.0256 min–1	hierarchical nanoflowers, Cu enrichment >93%, high stability (10 cycles)
Co–Cu MOF@NH2-cellulose	solvothermal + immobilization	tetracycline degradation via PMS	94.6% removal in 30 min; >85% retained after 5 cycles	Co–Cu synergy; SO4 •–, •OH, and 1O2 ROS identified
urchin-like CuxCe1–xOy-BTC (from the Cu–Ce MOF precursor)	solvothermal + calcination	catalytic ozonation of phenol	Cu0.5Ce0.5Oy-BTC: 99% phenol removal, 92% TOC in 60 min	Cu+/Cu2+ and Ce3+/Ce4+ cycling, •OH & •O2 – radicals
Pd@Cu2Ni-MOL ultrathin heterojunctions	substitutional synthesis + Pd NP loading	CO2 photoreduction	Pd1.5@Cu2Ni-MOL: 194.74 μmol/g CO (100% selectivity)	Cu–Ni polarization fields + Pd LSPR hot spots
SUM-23A, SUM-23B, SUM-33 Cu-MOFs (4-PyHA ligand)	Solvothermal	CO2 reduction to CO	SUM-33: ∼3.05 CO units (vs ∼0.02 for SUM-23B)	rod-shaped SUM-33 most active; robust stability
Cu-MOF@Hydrogel composite	hydrothermal + embedding in hydrogel	Cr(VI) and Congo Red degradation	94.7% Cr(VI) in 60 min; 92.3% CR in 75 min	hydrogel improves dispersion, stability, adsorption

10. Application of Cu-MOFs in Antibacterial Studies

Cu-MOFs have emerged as promising antibacterial materials due to the intrinsic antimicrobial properties of copper ions combined with the structural advantages of MOFs. − The controlled release of Cu²⁺ from the porous framework disrupts bacterial membranes, induces oxidative stress, and interferes with enzymatic activity, leading to effective inhibition of both Gram-positive and Gram-negative bacteria. In addition, the high surface area and tunable porosity of Cu-MOFs facilitate strong interaction with bacterial cells and allow incorporation of secondary agents such as antibiotics or photosensitizers to achieve synergistic effects. Cu-MOFs have also demonstrated excellent biofilm inhibition and potential against multidrug-resistant strains, particularly when designed to generate ROS under light or catalytic conditions. These multifunctional features make Cu-MOFs attractive candidates for next-generation antibacterial coatings, wound dressings, and biomedical applications.

Cu-MOFs of different sizes [30 nm (Cu-MOF-1), 40 nm (Cu-MOF-2), 50 nm (Cu-MOF-3), and ∼1 μm × 100 nm (Cu-MOF-4)] were obtained using variations in reaction temperature and time. Stability tests showed that smaller Cu-MOFs released more Cu ions (up to 20.3% for Cu-MOF-1 after 12 h), whereas larger Cu-MOFs were more hydrostable. Surface charge and hydrophobicity also varied with size, with Cu-MOF-4 exhibiting lower negative charge (−28.4 mV) and higher hydrophobicity, favoring heteroaggregation with algal cells. Functionally, particle size strongly influenced photocatalytic performance. At 60 mg/L under visible light, Microcystis aeruginosa growth inhibition reached 78.7% with Cu-MOF-4, compared to 71.2%, 68.9%, and 60.0% for Cu-MOF-3, Cu-MOF-2, and Cu-MOF-1, respectively. For microcystin degradation, Cu-MOF-4 achieved 70.4% removal in 12 h, whereas other Cu-MOFs demonstrated 2.6-fold, 1.8-fold, and 2.0-fold higher removal than Cu-MOF-3, Cu-MOF-2, and Cu-MOF-1. ROS analysis identified superoxide (O2^•–) and hydroxyl radicals (^•OH) as the dominant species driving algal inactivation and toxin breakdown. Cu-MOF-4 also demonstrated better reusability, with only a 38.9% performance loss after three cycles, compared to >70% loss in smaller MOFs. Overall, the work highlights that larger Cu-MOFs outperform smaller ones in stability, ROS generation, algal inhibition, and toxin degradation.

Cu-MOFs were synthesized via a room-temperature one-pot method using copper nitrate and trimesic acid in ethanol. The resulting nanostructures were further combined with graphitic carbon nitride (g-C₃N₄) to construct a Cu-MOF/g-C₃N₄ heterojunction photocatalyst. Physicochemical characterization confirmed a uniform morphology, high crystallinity, and effective coupling between Cu-MOF and g-C₃N₄, which enhanced light absorption and charge separation efficiency. Stability and leaching tests indicated minimal Cu ion release, ensuring safety for biomedical applications.

Functionally, the Cu-MOF/g-C₃N₄ photocatalyst exhibited outstanding antibacterial and wound-healing performance. Under visible light, it achieved 99.99% inactivation of Escherichia coli and S. aureus within 20 min, driven by ROS generation (^•OH, O₂ ^•–, and ¹O₂). In vivo experiments showed accelerated wound closure, with the treated group reaching 95% wound healing within 10 days, compared to 62% in the control group. Histological analysis confirmed enhanced collagen deposition and new tissue formation. Importantly, the photocatalyst retained >90% antibacterial efficiency after five cycles, demonstrating strong reusability and stability.

A biomimetic Cu-MOF composite was created by integrating copper-based MOFs with glucose oxidase (GOx) and hyaluronic acid (HA). The MOFs were prepared via a facile coordination method between copper ions and 2-methylimidazole, producing uniform nanoscale frameworks. Subsequent surface functionalization with HA improved stability and bacterial targeting, while GOx immobilization endowed the composite with cascade catalytic abilityconverting glucose into H₂O₂, which was then activated by Cu-MOFs through Fenton-like reactions to generate highly toxic ^•OH radicals. In terms of outcomes, the Cu-MOF/GOx/HA platform demonstrated 99.3% bacterial inactivation of E. coli and S. aureus within 10 min under physiological conditions. ROS quantification verified strong ^•OH generation, synergistically enhanced by the cascade reaction. In vivo experiments demonstrated remarkable wound-healing efficacy, with over 90% closure achieved within 12 days, compared to less than 60% closure in untreated controls. Histological analysis revealed denser collagen deposition and better tissue regeneration in treated wounds. Importantly, the system maintained >85% antibacterial efficiency after four reuse cycles, highlighting its durability and potential for biomedical applications.

A simple room-temperature coordination reaction between copper nitrate and trimesic acid in ethanol resulted in the formation of nanoscale Cu-MOF crystals with uniform morphology and high surface area, mimicking the activity of natural oxidase enzymes. Structural analyses confirmed the successful assembly of the crystalline Cu-MOFs, while catalytic assays verified their oxidase-like properties without requiring additional cofactors or external stimuli. Functionally, the Cu-MOFs showed highly efficient antibacterial performance. They generated ROS directly in aqueous solution, achieving >99% killing efficiency against both Gram-negative E. coli and Gram-positive S. aureus within 20 min. Minimum inhibitory concentration tests revealed values as low as 25 μg/mL, underscoring strong bactericidal potency. In addition, live/dead staining and electron microscopy confirmed severe bacterial membrane damage. Importantly, the Cu-MOFs exhibited negligible cytotoxicity toward mammalian cells at effective antibacterial concentrations, highlighting their biocompatibility and potential as alternative antimicrobial agents (See Table ).

8. Application of Cu-MOFs in Antibacterial Studies.

Cu-MOF/composite	target bacteria	mechanism of action	key outcomes	reference
nanoscale Cu-MOF (Cu–BTC, RT synthesis)	E. coli, S. aureus	oxidase-mimicking; ROS generation without cofactors	>99% killing in 20 min; MIC = 25 μg/mL; confirmed membrane damage; negligible cytotoxicity to mammalian cells
NH2–Cu-MOF	E. coli, S. aureus	controlled Cu2+ release, membrane disruption, ROS generation	strong antibacterial activity; effective against Gram + and Gram-bacteria
Cu-MOFs (size-dependent: Cu-MOF-1 to Cu-MOF-4)	Microcystis aeruginosa (algal bacteria-like cells)	ROS (•O2 –, •OH), Cu2+ ion release	larger Cu-MOF-4 showed the best stability, ROS generation, and 78.7% growth inhibition
Cu-MOF/AgCl–Ag composite	E. coli	irradiation-enhanced ROS + Ag+ and Cu2+ synergy	superior antibacterial activity compared to pristine Cu-MOF
Cu-MOF/g-C3N4 heterojunction	E. coli, S. aureus	visible-light-driven ROS (•OH, •O2 –, 1O2)	99.99% inactivation within 20 min; 95% wound healing in 10 days (in vivo)
Cu-MOF/GOx/HA biomimetic composite	E. coli, S. aureus	cascade catalysis: Glucose → H2O2 (GOx) → •OH (Cu-MOF Fenton-like)	99.3% bacterial inactivation within 10 min; improved wound healing
Cu(II)-MOF@Fe3O4 hybrid	broad-spectrum	synergistic Cu2+ and magnetic Fe3O4 particles	excellent antimicrobial performance with magnetic recyclability
Cu/Zn-MOF with 1,3,5-tris(styryl)benzene tricarboxylate	broad-spectrum	Cu2+ and Zn2+ antibacterial synergy	high antibacterial efficacy, stable frameworks

11. Mechanistic Insights into Cu-MOF-Based Catalysis

The catalytic performance of Cu-MOFs arises from the unique interplay between redox-active Cu nodes, conjugated organic linkers, and the accessible porous microenvironment that facilitates mass and charge transport. While numerous studies have reported impressive conversion rates and product selectivity, a mechanistic understandingdetailing the roles of active sites, electron-transfer pathways, and reaction intermediatesis essential for the rational design of next-generation Cu-MOF catalysts.

Although extensive catalytic data have been reported for Cu-MOFs, understanding the fundamental reaction mechanisms remains crucial for correlating structural features with activity. Mechanistic elucidation requires identification of the nature of the active sites, the electron-transfer pathways, and the reaction intermediates that govern selectivity and turnover frequency. Cu-MOFs typically possess several types of catalytically active centers, each contributing differently depending on the reaction environment (thermal, electrochemical, or photochemical).

11.1. Coordinatively Unsaturated Cu­(II) Sites

Generated during activation by removing terminal solvent molecules (e.g., H₂O and DMF) from the paddlewheel [Cu₂(O₂CR)₄] SBUs. These sites act as Lewis acid centers that adsorb and polarize reactant molecules. In oxidation reactions, such as CUS, facilitate the activation of O₂, forming Cu–O₂ adducts capable of hydrogen abstraction. ,

11.2. Redox-Coupled Cu⁺/Cu²⁺ Pairs

Cu ions can undergo reversible one-electron transformations, enabling sequential redox cycles that mimic enzymatic processes. , For example, Cu²⁺ accepts an electron to form Cu⁺, which in turn activates oxygen or other oxidants, regenerating Cu²⁺. The coexistence of Cu⁺ and Cu²⁺ enhances the catalytic turnover frequency (TOF) by ensuring continuous redox cycling.

11.3. Cu–O–C Linker Interfaces

The strong orbital coupling between Cu 3d and linker π orbitals forms an electron-delocalized coordination environment. These sites often mediate charge transport between adjacent Cu centers, enabling long-range electron hopping that supports multielectron reactions such as CO₂ reduction or oxygen evolution.

11.4. Defect-Rich and Doped Sites

Introducing heteroatoms (Ni, Ce, Fe, Co, or Zn) or deliberately creating vacancies alters local electronic density, producing under-coordinated Cu–O sites with enhanced adsorption affinity for small molecules (CO₂, NO₃ ^–, or O₂). DFT studies have confirmed that such defects lower the energy barrier for key reaction steps by 0.3–0.6 eV compared to perfect lattices.

11.5. Metal–Support Interfaces in Composites

When Cu-MOFs are combined with conductive supports (graphene, CNTs, TiO₂, and g-C₃N₄), interfacial heterojunctions promote charge separation and migration. − Electrons preferentially move toward Cu centers, while holes are transported through the support, thereby suppressing recombination and increasing the redox efficiency.

The dispersion and oxidation states of these sites are often confirmed by XPS, EPR, and in situ X-ray absorption spectroscopy (XAS), which show reversible Cu²⁺/Cu⁺ transitions during catalytic cycles. Cu-MOFs mediate reactions through distinct electron-transfer mechanisms depending on whether the process is thermally, electrochemically, or photochemically driven.

In thermal oxidation or reduction reactions, the Cu²⁺/Cu⁺ redox pair acts as an electron shuttle. The process can be described as a modified Mars–van Krevelen mechanism.

11.5.1. Substrate Activation

The substrate (R–H) adsorbs onto an open Cu²⁺ site. Electron transfer from R–H to Cu²⁺ generates a carbon-centered radical (R^•) and Cu⁺.

$${\mathrm{C}\mathrm{u}}^{2+}+\mathrm{R}-\mathrm{H}\to {\mathrm{C}\mathrm{u}}^{+}+{\mathrm{R}}^{·}+{\mathrm{H}}^{+}$$

11.5.2. Oxygen Activation

The reduced Cu⁺ site binds O₂ to form a superoxide species (Cu²⁺–O₂ ^•–) or peroxide intermediate.

$${\mathrm{C}\mathrm{u}}^{+}+{\mathrm{O}}_2\to {\mathrm{C}\mathrm{u}}^{2+}-{\mathrm{O}}_2^{·-}$$

11.5.3. Radical Coupling/Product Formation

The substrate radical reacts with surface O₂ ^•– or OH^• intermediates to form oxidized products (ROOH, RO).

$${\mathrm{R}}^{·}+{\mathrm{C}\mathrm{u}}^{2+}-{\mathrm{O}}_2^{·-}\to \mathrm{R}\mathrm{O}\mathrm{O}\mathrm{H}\to \mathrm{R}\mathrm{e}5\mathrm{f}\mathrm{b}\mathrm{O}$$

11.5.4. Cycle Regeneration

The oxidized Cu²⁺ is restored to its initial state, completing the redox loop.

Kinetic isotope effect studies (k_H/k_D ≈ 2–3) and in situ EPR detection of superoxide radicals (g = 2.07) confirm that C–H activation and O₂ reduction are rate-limiting steps mediated by Cu²⁺/Cu⁺ redox cycling.

In electrochemical CO₂ reduction (CO₂RR) or nitrate reduction (NO₃ ^– → NH₃), electrons are supplied externally, and the reaction rate depends on Cu site coordination, defect density, and electronic conductivity of the MOFs. Key intermediates identified via in situ FT-IR and Raman spectroscopy include COOH, CO, and CHO species for the CO₂RR, NO₂ ^–, NH₂OH, and NH₃ for the NO₃RR. For the CO₂RR, DFT and experimental evidence suggest the following steps

$$\begin{array}{l}{\mathrm{C}\mathrm{O}}_2+{\mathrm{e}}^{-}+{\mathrm{H}}^{+}\to {}^{*}\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}\\ {}^{*}\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}+{\mathrm{e}}^{-}+{\mathrm{H}}^{+}\to {}^{*}\mathrm{C}\mathrm{O}+{\mathrm{H}}_2\mathrm{O}\\ 2^{*}\mathrm{C}\mathrm{O}\to {}^{*}\mathrm{O}\mathrm{C}\mathrm{C}\mathrm{O}\to {\mathrm{C}}_2{\mathrm{H}}_4\text{or}{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{O}\mathrm{H}\end{array}$$

The Cu–Cu dual sites and under-coordinated Cu–O defects lower the activation barrier for CO dimerization, a rate-determining step in C–C coupling. In bimetallic systems (e.g., Ni–Cu or Pd–Cu MOFs), the secondary metal tunes the electronic structure of Cu, shifting the d-band center and facilitating faster electron transport and intermediate stabilization.

In photocatalytic degradation and CO₂ reduction, the metal–organic interface serves as a light-harvesting and charge-separation junction. , Mechanistically, light absorption by organic linkers or Cu ligand charge-transfer bands (MLCT/LMCT) generates electron–hole pairs. Electrons transfer from linker orbitals (LUMO) to Cu centers or embedded semiconductors (TiO₂, g-C₃N₄), while holes remain in the linker or are scavenged by adsorbed donors. The surface reaction involves electrons reducing CO₂ → CO/CH₄/CH₃OH via CO₂ ^– intermediates. Holes oxidize H₂O or organics → O₂ or reactive radicals. Transient photoluminescence and time-resolved spectroscopy show that heterojunction formation (e.g., Cu-MOFs/TiO₂) extends charge-carrier lifetimes from nanoseconds to microseconds, thus improving photocatalytic efficiency (see Table ).

9. Identification of Reaction Intermediates.

reaction type	detected/proposed intermediates	experimental evidence	mechanistic implication
oxidation of hydrocarbons	O2 –, OH•, ROOH, Cu+ species	EPR and XPS: transient Cu+ signals, g = 2.07	redox cycling between Cu2+/Cu+ drives radical formation
CO2 electroreduction	COOH, CO, OCCO, CHO	In situ FT-IR bands at 1650–1800 cm–1 (COOH)	dual Cu–Cu sites stabilize CO intermediates for C–C coupling
nitrate reduction	NO2 –, NH2OH, NH3	Raman shifts at 1040–1070 cm–1	Cu+ facilitates stepwise proton–electron transfer
photocatalytic dye degradation	O2 –, •OH, H2O2	trapping experiments and PL quenching	photoinduced holes oxidize water; electrons reduce O2 → radicals
glycerol oxidation (GOR)	CH2OHCHO, HCOOH	HPLC and GC–MS	Cu–O–H active sites enable partial oxidation via α-C–H activation

The organic linker in Cu-MOFs is not a passive spectator; its π-conjugated system contributes to electron delocalization and charge mediation between metal centers. DFT studies reveal that the LUMO of carboxylate or catecholate linkers overlaps with Cu 3d orbitals, facilitating metal–ligand charge transfer (MLCT). Functional groups (−NH₂, −OH, and −SO₃H) alter electron density, thereby modifying the adsorption energies of reactants. In mixed-ligand systems, the electronic coupling between linkers creates efficient charge-transport channels, reducing recombination losses in photocatalytic reactions.

When Cu-MOFs are combined with other materials (carbon, TiO₂, g-C₃N₄, and MXenes), heterojunction interfaces enhance charge separation. The conduction-band alignment between the MOF and the semiconductor allows unidirectional electron flow toward the cocatalyst and holes toward the oxidant. Cu-MOF/TiO₂ heterojunctions exhibit downward band bending that promotes electron migration from TiO₂ → Cu-MOF, favoring the reduction of CO₂. Cu-MOF/graphene composites display decreased charge-transfer resistance (R_ct) from 5.8 to 1.9 Ω, improving electron mobility and catalytic kinetics (see Table ).

10. Summary of Mechanistic Correlations.

catalysis type	dominant active sites	primary electron pathway	key intermediates	structure–activity relationship
thermal oxidation	Cu2+/Cu+ pairs, CUS	Cu2+ ↔ Cu+ redox cycling via substrate oxidation	O2 –, ROOH	high crystallinity and open metal sites enhance redox turnover
electrocatalysis (CO2RR, NO3RR, OER/HER)	under-coordinated Cu–O/Cu–Cusites; defect centers	electron tunneling through Cu cluster and conjugated linker	COOH, CO, NO2 –, NH2OH	defects and dual-metal centers promote multielectron transfer
photocatalysis	Cu–O cluster, linker π orbitals, heterojunction interface	photoexcited charge separation across Cu–linker/semiconductor	CO2 –, O2 –, OH•	band alignment and linker functionalization enhance charge lifetime

12. Distinct Advantages of Cu-MOFs over Other Earth-Abundant Metal-Based MOFs

Cu-MOFs provide several distinctive advantages over other earth-abundant metal MOFs such as Fe-, Co-, Ni-, and Zn-based frameworks. − The most fundamental benefit arises from the dual redox flexibility of copper (Cu⁺/Cu²⁺) under mild reaction conditions. This capability enables Cu-MOFs to catalyze multielectron processes and stabilize transient intermediates, allowing higher selectivity in oxidation, reduction, and organic transformation reactions. In contrast, Zn-MOFs are typically redox-inactive, Fe-MOFs can induce undesired Fenton-like pathways, and Ni/Co-MOFs often require high overpotentials to switch redox states. Additionally, Cu-MOFs possess abundant accessible active sitesmononuclear Cu centers as well as multinuclear Cu₂/Cu₃ clusterswhich promote stronger chemisorption and substrate activation, resulting in superior efficiency in classical heterogeneous catalysis such as selective alcohol oxidation, CO oxidation, and hydrocarbon functionalization.

In photocatalysis, Cu-MOFs demonstrate remarkable activity due to their strong ligand-to-metal charge transfer (LMCT) features and excellent visible-light absorption. ,, While Fe-MOFs also absorb broadly in the visible region, they often suffer from rapid electron–hole recombination, limiting photocatalytic efficiency. Zn-MOFs, on the other hand, show weak charge-transfer characteristics and minimal visible-light activity unless modified. Cu-MOFs, especially when combined with semiconductors (TiO₂, g-C₃N₄) or carbon-based materials (graphene, CNTs), facilitate efficient charge separation and electron transfer, resulting in improved photocatalytic hydrogen evolution, organic pollutant degradation, and CO₂ photoreduction. Their photocatalytic stability can also surpass that of Fe-MOFs, which degrade faster through ligand oxidation under prolonged illumination.

For electrocatalysis, Cu-MOFs offer high site density, tunable coordination environments, and low activation barriers for intermediate formation. These features lead to excellent performance in reactions, such as CO₂ reduction (CO₂RR), oxygen evolution (OER), hydrogen evolution (HER), nitrate reduction (NO₃RR), and nitrogen reduction (NRR). Unlike Zn-MOFs, which are nonconductive, Cu-MOFs can be tuned electronically through defect creation, mixed-valent Cu sites, or hybridization with conductive supports. Although their inherent conductivity may still be moderate, Cu-MOFs can readily convert to MOF-derived carbon/oxide composites, retaining the uniform copper site distribution and significantly improving electron mobility. The Cu⁺/Cu²⁺ redox couple also plays a crucial mechanistic role in stabilizing CO₂RR intermediates, making Cu-MOFs more selective toward multicarbon products compared to Co- or Ni-based MOFs.

In antibacterial applications, Cu-MOFs provide a combination of antimicrobial ion release, ROS generation, and membrane damage pathways that outperform many other earth-abundant metal MOFs. Zinc is a biocompatible element, but Zn-MOFs rely mainly on ion release and show weaker oxidative stress generation. Fe-MOFs may induce ROS in a Fenton-like manner but lack controlled release and sometimes lead to biocompatibility concerns. Copper, however, has inherent broad-spectrum antimicrobial behavior, damaging bacterial membranes, denaturing proteins, and binding to nucleic acids. Cu-MOFs slowly release Cu²⁺ ions while simultaneously generating ROS, offering durable bactericidal action. Their porous and high-surface-area structure enhances physical interaction with bacterial cells, while MOF composition prevents excessive or toxic burst release common in soluble Cu-salts.

From a materials engineering perspective, Cu-MOFs are highly tunable, enabling control over hydrophilicity and hydrophobicity, electron density, interfacial interactions, and active site spacing. Compared to Fe-, Co-, Ni-, and Zn-MOFs, the coordination chemistry of copper allows easier introduction of catalytically relevant functionalities through linker engineering, mixed-metal doping, or construction of hierarchical porous morphologies. This tunability translates to improved catalytic and electrocatalytic kinetics, enhanced light harvesting, and sustained antibacterial activity. Moreover, copper is abundant, low-cost, and less toxic compared to many transition metals used in catalytic platforms, further enhancing its practical appeal.

Taken together, the combination of accessible redox-active Cu sites, visible-light responsive electronic structure, multielectron reaction capability, and intrinsic antimicrobial properties uniquely positions Cu-MOFs among earth-abundant MOF systems. Their versatility across catalysis, photocatalysis, electrocatalysis, and antibacterial applications makes Cu-MOFs not only scientifically promising but also practically scalable for environmental remediation, green energy, chemical synthesis, and biomedical uses (Table ).

11. Comparative Performance of Cu-MOFs vs Other Earth-Abundant MOFs.

parameter/application	Cu-MOFs	Fe-MOFs	Co-MOFs	Ni-MOFs	Zn-MOFs
redox activity	Cu+/Cu2+ reversible → high flexibility	multiple redox states but uncontrolled pathways (Fenton-like)	Co2+/Co3+ but higher overpotential	Ni2+/Ni3+ redox, high overpotential	redox-inactive
catalytic selectivity	high due to site uniformity and Cu clusters	moderate, often side reactions	moderate	moderate	low due to weak activation
active site accessibility	open Cu sites + multinuclear clusters	limited accessibility	limited accessibility	limited accessibility	mostly closed sites
thermal catalysis	high activity and selectivity at mild–moderate T	good but stability under liquid media limited	moderate	lower	weak catalytic ability
photocatalysis potential	excellent LMCT and visible absorption	visible absorbing but fast recombination	poor light absorption	poor light absorption	weak visible-light activity
charge separation in hybrids	strong when paired with TiO2/CNTs/graphene	moderate	moderate	moderate	weak
electrocatalysis efficiency	high → suitable for CO2RR, OER, NO3RR	good but stability issues	moderate	moderate	very poor (insulating)
electrical conductivity (intrinsic)	moderate, improved via hybridization	low	low–moderate	low	very low
antibacterial properties	strong (Cu2+ release + ROS generation)	weak–moderate (Fenton ROS)	poor	poor	weak (biocompatible metal)
material stability	good; tunable with composites	sensitive to pH	sensitive	sensitive	very stable but catalytically weak
cost/availability	very low and earth abundant	low	moderate	moderate	low
tunable functionality	high (doping, defects, hybrids)	moderate	moderate	moderate	low
scalability for applications	high	moderate	moderate	moderate	low

13. Outlook and Challenges

Copper-based MOFs have proven to be multifunctional materials with outstanding potential in catalysis, energy conversion, storage, and sensing. Their unique combination of open porosity, tunable metal coordination, and redox-active sites enables them to outperform many traditional materials in terms of catalytic efficiency and sensing sensitivity. Over the past decade, significant progress has been achieved in developing advanced synthesis methods to control particle size, morphology, and stability, thereby enhancing the electrochemical conductivity and catalytic performance of Cu-MOFs. Furthermore, integration with conductive supports, carbon-based nanomaterials, and metal/metal oxide nanoparticles has demonstrated promising strategies for overcoming the inherent conductivity limitations.

Despite significant progress in the synthesis, characterization, and catalytic applications of Cu-MOFs, several scientific and technological challenges remain unsolved. The next decade of research must aim to bridge the gap between laboratory-scale discovery and real-world catalytic implementation. To achieve this, future investigations should focus on mechanistically guided material design, multifunctionality, and data-driven screening strategies.

Below are the key forward-looking research priorities and technical pathways identified for the future development of Cu-MOF-based catalysts. A major Frontier lies in designing stimuli-responsive Cu-MOFs whose structures and activities can be reversibly tuned by external triggers such as light, temperature, electric field, or pH. Incorporating photochromic linkers (e.g., azobenzene and spiropyran) can enable in situ modulation of pore aperture and charge density, dynamically controlling reactant access and catalytic turnover. Integration of redox-active ligands or ferromagnetic Cu-based nodes may allow the tuning of oxidation states and spin alignment, enhancing selective catalysis under applied fields. Using flexible linkers (polyether or amide segments) can induce framework “breathing” effects, improving substrate diffusion and regenerability in temperature-coupled reactions. Such adaptive architectures will enable Cu-MOFs to behave as “intelligent catalysts”, capable of real-time self-optimization under fluctuating reaction conditions.

The integration of biological functionality into Cu-MOFs represents a transformative approach to selective and sustainable catalysis. Immobilizing oxidoreductases, laccases, or peroxidases within Cu-MOF matrices can combine the selectivity of biocatalysts with the robustness of inorganic frameworks. Peptide-based linkers containing histidine or cysteine residues can emulate natural copper enzyme active sites (e.g., tyrosinase and superoxide dismutase). Hybrid Cu–BioMOFs could mimic metalloenzyme pathways for CO₂ reduction or oxidative detoxification of pollutants under mild aqueous conditions. These biohybrid materials open new directions for green catalysis, biosensing, and biomedical redox regulation applications.

Given the enormous structural diversity of MOFs, data-driven and computational screening will be indispensable in identifying next-generation Cu-MOFs with the desired activity, selectivity, and stability. Combining DFT with molecular dynamics simulations can predict the adsorption energies, reaction barriers, and stability windows for thousands of hypothetical Cu-MOF structures. Trained on experimental and computational data sets, ML models can predict performance metrics such as activation energies, CO₂ binding affinity, or charge-transport coefficients. Coupling ML with robotic synthesis platforms may enable closed-loop experimentation, where predictive algorithms guide parameter selection (solvent, temperature, and precursor ratio) for optimal Cu-MOF fabrication. Such AI-assisted frameworks will accelerate discovery cycles, minimize experimental trial-and-error, and unlock previously unexplored structure–property relationships.

The formation of well-defined heterointerfaces remains one of the most promising strategies to boost the charge transport and catalytic selectivity in Cu-MOFs.

Future work should explore controlled band alignment with materials such as TiO₂, ZnO, g-C₃N₄, and MXenes, which can create directional charge-transfer pathways that suppress recombination and favor multielectron transformations (e.g., CO₂ → CH₄, NO₃ ^– → NH₃). Graphene or carbon nanotube supports enhance the conductivity, mechanical strength, and electron mobility. Precisely anchored Cu–N₄ or Cu–O₄ moieties can mimic homogeneous catalysts while maintaining solid-state stability. The systematic correlation among interface composition, electronic band structure, and catalytic turnover remains an essential target for mechanistic understanding.

While stability issues are well-documented, next-generation research should move beyond passive reinforcement and actively exploit defects and dynamic coordination as functional tools. Creating oxygen vacancies or linker deficiencies in a regulated manner can increase the active-site density without compromising crystallinity. Introducing fluorinated, sulfonated, or alkyl-substituted linkers can shield Cu sites from hydrolysis while maintaining accessibility. Surface coating with polymeric or inorganic layers (e.g., PDMS, SiO₂, and TiO₂) offers long-term protection under humid or acidic conditions. Advanced in situ spectroscopy and theoretical modeling should be employed to map how these modifications influence the Cu-oxidation states and charge transport.

For Cu-MOFs to progress from proof-of-concept catalysts to deployable technologies, integration into functional devices is critical. Promising directions include the fabrication of Cu-MOF-based electrodes with high conductivity and structural stability for continuous CO₂ electroreduction at industrially relevant current densities. Embedding Cu-MOFs in polymeric membranes for simultaneous catalysis and separation, enhancing process efficiency. Hybrid Cu-MOF/semiconductor architectures capable of harnessing solar energy for water splitting and pollutant degradation. Cu-MOF thin films or hydrogels that detect gases, redox biomarkers, or environmental pollutants via colorimetric or electrochemical responses. Such device-level realization will demand advances in scalable film deposition, interface adhesion, and long-term operational durability.

Deeper mechanistic understanding will depend on the real-time characterization of Cu-MOFs under working conditions. Future studies should employ operando XAS to track the Cu-oxidation state changes. Time-resolved infrared (TR-IR) and Raman spectroscopy were used for detecting transient intermediates. Environmental TEM and AFM were used to visualize structural evolution during catalysis. Combining these with theoretical modeling will enable dynamic mapping of electron–proton transfer pathways, guiding rational design principles.

Finally, Cu-MOF research must embrace a sustainability-oriented design. Future strategies include using earth-abundant precursors and green solvents (e.g., deep eutectic solvents, water, or supercritical CO₂). Developing recyclable and self-healing MOF catalysts recover activity after degradation. Exploring MOF-based catalytic cascades that integrate multiple reaction steps in a single, regenerable platform. This aligns with the broader objective of establishing closed-loop catalytic systems that combine efficiency, environmental compatibility, and economic viability.

The authors declare no competing financial interest.