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. 2026 Sep 26. Online ahead of print. doi: 10.1039/d6sc04635e

A non-enantiopure H8-BINOL metal–organic framework for enantioselective fluorescence sensing

Pattara Siripanich a, Jierui Zhang b, Katelyn M Clutterbuck c, Girish Lakhwani c, Martina Lessio b, Carol Hua a,✉
PMCID: PMC13635996  PMID: 42835507

Abstract

Effective chiral sensing and separation fundamentally rely upon using chiral materials, providing environments capable of selectively recognising and discriminating between enantiomers. However, enantiopure materials are often synthetically demanding and costly due to the difficulty of separating enantiomers. Here, we demonstrate that non-enantiopure materials can function effectively as chiral sensors when exhibiting non-inversion enantioselectivity. Fluorescent Cd(ii) metal–organic frameworks (MOFs) based on H8-BINOL ligands were synthesised in both enantiopure ((S)-1-Cd and (R)-1-Cd) and scalemic ((sca)-1-Cd) forms and evaluated for enantioselective sensing of aspartic acid dimethyl ester (Asp-diMe). Both enantiopure MOFs displayed similar enantioselectivity without inversion (er = 4.26 and 2.00), while the scalemic analogue retained measurable enantioselectivity (er = 2.11) and enabled detection of varying enantiomeric compositions. Computational studies revealed that the enantioselectivity arises from the interplay between chiral pore environments and solvent-controlled accessibility of binding sites. These findings provide new insights into the role of pore structure and solvent in governing enantioselective recognition. Non-inversion enantioselectivity is established as a potential design for chiral sensing using non-enantiopure materials, enabling a viable and cost-effective alternative to enantiopure systems.

Non-inversion enantioselectivity, as exhibited by H8-BINOL containing MOFs allows the use of non-enantiopure systems as fluorescent chiral sensors enabling a cost-effective alternative to enantiopure systems.graphic file with name d6sc04635e-ga.webp

Introduction

Chiral molecules have a central role across chemistry, biology, and materials science as the two enantiomeric forms of a compound can exhibit markedly different behaviours in asymmetric environments. This is particularly critical in pharmaceuticals,1 where one enantiomer may display the desired therapeutic effect while the other is inactive or even harmful,2 emphasising the need for precise chiral recognition and separation. Chiral sensors are of growing importance,3–5 enabling the rapid, sensitive, and selective detection of specific enantiomers in complex mixtures for applications in drug development,6,7 environmental monitoring,8 and food analysis.9,10

Metal–organic frameworks (MOFs) incorporating luminescent or fluorescent components have been a promising platform for chiral sensing11–17 exhibiting excellent enantioselective responses with some of the highest values reported.11 The host–guest interactions within the fluorescent MOF's well-defined porous structure can induce enantiomer-dependent changes in emission intensity, wavelength, or lifetime. MOFs have high surface areas, tunable pore environments, and structural modularity, which allow precise incorporation of chiral features and control over recognition sites.18,19

A challenge in the development of chiral sensors (and other enantioselective applications) is the requirement of an enantiopure compound with chiral environments that can enable an enantioselective response.20 The synthesis of chiral compounds is challenging due to their similar physical properties in non-chiral environments, often requiring extensive purification and separation. The generation of an enantioselective response in MOFs has to date, required inclusion of at least one chiral component.21–23

5,5′,6,6′,7,7′,8,8′-Octahydro-1,1′-bi-2-naphthol (H8-BINOL) contains axial chirality and is synthesized by reducing the aromatic rings in 1,1′-binaphthol (BINOL). The additional steric hindrance afforded by the aliphatic ring has yielded enhanced enantioselectivity in catalytic applications.24 Only a few reports on the enantioselectivity of H8-BINOL currently exist.24–26 The enantioselectivity of H8-BINOL is unique as it does not follow the usual trend of inverse enantioselectivity when interacting with amino acids and amino alcohols.25,26 Inverse enantioselectivity refers to the phenomenon where switching the chiral form of a sensor reverses its preference for the opposite enantiomer of a target molecule, as a result of stereospecific interactions.27–29 For example, an (S)-enantiomer sensor may favourably interact with the (R)-analyte, and an (R)-enantiomer sensor will typically interact more favourably with the (S)-analyte. The unique chiral non-inversion of H8-BINOL suggests that a racemic mixture or compound could potentially yield an overall chiral system and enable chiral sensing using a non-enantiopure material.

Herein, we report the synthesis of a Cd(ii) MOF containing H8-BINOL and assess its ability to act as a chiral fluorescent sensor with aspartic acid dimethyl ester. The Cd(ii) MOF was made separately with both (R)- and (S)-H8-BINOL enantiomers as well as racemic H8-BINOL to determine if the material exhibited chiral non-inversion. Circular dichroism experiments were completed to assess the chirality of the materials whilst computational calculations yielded insights towards the mechanism of enantioselectivity within the voids of the MOF.

Results and discussion

Synthesis and structure

[Cd2(L)2(DMF)2(H2O)2·DMF] (1-Cd) was synthesized using 5,5'-[[5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthalene]-2,2′-diylbis(oxymethylene)]bis(1,3-benzenedicarboxylic acid) (L) and Cd(NO3)2·4H2O in a 1 : 1 ratio of DMF and H2O for 2 days at 70 °C resulting in clear colourless needle crystals of 1-Cd. Single-crystal X-ray diffraction (SCXRD) studies revealed that (S)-1-Cd and (R)-1-Cd, synthesized using (S)-L and (R)-L respectively, are isostructural, with both crystallizing in the orthorhombic space group, P212121. Using (rac)-L yielded a scalemic mixture of 1-Cd ((sca)-1-Cd), however the crystal structure could not be determined due to its poor diffraction quality but was isostructural to (S)-L and (R)-L from powder X-ray diffraction (PXRD) experiments (Fig. S11).

The structure of (S)-1-Cd and (R)-1-Cd contains binuclear Cd clusters where each pair of Cd(ii) atoms is bridged by two carboxylate groups from the ligand (L). Each Cd(ii) complex is formed in distorted octahedral geometry coordinated by six O-donors including two from the carboxylate group, two from the bridging carboxylate, one from water and one from DMF (Fig. 1a). The bond distances of 2.26(1)–2.43(1) Å for Cd(ii)–O from the carboxylate ligand, 2.320(9) Å for Cd(ii)–O from water and 2.30(1) Å for Cd(ii)–O from DMF are observed. The H8-BINOL ligand (L) consists of four carboxylate groups that link to four Cd(ii) binuclear clusters resulting in each cluster connecting to eight neighbouring clusters (Fig. 1b). This arrangement allows the structure to expand into 2D sheets that are packed in an ABAB pattern along the a-axis (Fig. 1c). (S)-L and (R)-L structures are crystallographically disordered due to the conformational flexibility of the cyclohexyl ring on H8-BINOL.

Fig. 1. The structure of (S)-1-Cd showing (a) the Cd(ii) binuclear clusters and ligand ((S)-L). Atoms are depicted as follows, carbon = black, nitrogen = blue, oxygen = red, cadmium = green. (b) The connectivity of the Cd(ii) binuclear clusters (yellow sphere = Cd(ii) binuclear cluster, blue rod = 1,3-dicarboxylate benzene linkage, green rod = long connection through H8-BINOL ligand, red rod = the eight connections of the binuclear cluster to neighbouring binuclear clusters), (c) 2D-packing structure in an ABAB arrangement as viewed from the a-axis.

Fig. 1

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Each unit cell contains four hexagonal shaped channels (Fig. S21b), and adjacent to these channels, there are eight pocket-like cavities (Fig. S21c). Within each hexagonal channel, two DMF molecules and four water molecules are directly coordinated to the Cd(ii) sites. In contrast, each of the pocket-like cavities contains one Cd(ii) directly coordinated by a single DMF molecule. The void space calculation was performed using single crystal data with a probe radius of 1.2 Å and grid spacing of 0.3 Å. The calculation showed an accessible void of 10.7% (1007.48 Å3) excluding the lattice solvents. The calculated minimum and maximum pore diameter were 1.34 Å and 4.37 Å, respectively. The thermogravimetric analysis (TGA) of (S)-1-Cd, (R)-1-Cd and (sca)-1-Cd each showed a mass loss of approximately 5% below 120 °C that is attributed to the loss of lattice DMF. A further mass loss around 20% between 120 °C to 300 °C is due to the release of the coordinated DMF molecules. Decomposition occurred above 350 °C (Fig. S12).

Challenges in achieving a pure racemic mixture MOF

(rac)-L was used to synthesize a presumed racemic mixture of 1-Cd. The resulting product was obtained as a microcrystalline powder, which was confirmed to be isostructural to (S)-1-Cd, (R)-1-Cd by PXRD (Fig. S11). Circular dichroism (CD) spectroscopy was used to investigate whether the product was a racemic mixture. For comparison, reference samples of the enantiopure (S)-1-Cd and (R)-1-Cd were prepared and measured at the same concentration (Fig. 2a).

Fig. 2. Suspension-state CD spectra of (a) (S)-1-Cd and (R)-1-Cd (b) (sca)-1-Cd synthesized from three independent batches (c) (sca)-1-Cd synthesized by seeding with (S)-1-Cd or (R)-1-Cd. The corresponding gabs values at the peak CD signals are indicated in the figure.

Fig. 2

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Suspension-state CD measurements were performed on three independently synthesized batches of 1-Cd obtained from (rac)-L (Fig. 2b). Unexpectedly, the CD spectra revealed non-zero signals, indicating the presence of an enantiomeric excess in the supposedly racemic MOF. This suggests that the product is not an exact 1 : 1 mixture of (S)- and (R)-enantiomers. These findings imply that the crystallization process may have been slightly biased toward one enantiomer, despite the use of a racemic starting material. This enantiomeric enrichment may arise due to secondary crystal nucleation.

Secondary crystal nucleation refers to the process where an existing crystal induces the formation of new nuclei, resulting in an accelerated crystallization rate.30 This mechanism is known to be autocatalytic, where loosely associated molecular clusters in solution adsorb onto the surface of a seed crystal, which serves as a structural template. The interaction stabilizes these clusters and promotes their rearrangement into an ordered crystalline form, effectively bypassing the higher energy barrier required for primary nucleation.31

Given that secondary nucleation is templated, it is reasonable to expect that the chirality of the initial seed crystal could influence the handedness of the crystals formed. To test this hypothesis, seeded crystallization experiments were performed by adding small amounts of either (S)-1-Cd or (R)-1-Cd crystals to the reaction mixture of (rac)-L and Cd(ii) under the same solvothermal conditions. The CD spectra of the seeded samples (Fig. 2c) clearly demonstrate an amplified response relative to the unseeded results (Fig. 2b), as reflected by an approximate five time increase in the dissymmetry ratio, gabs (=ΔA/A), defined as the ratio between differential absorbance of left- and right-circularly polarized light, ΔA (=AL − AR) and net absorbance, A. The absorptive dissymmetry factor (gabs) is used here in preference to the raw CD intensity as it provides an intensive figure of merit for the intrinsic chiroptical response, independent of sample concentration, path length and absorptive strength. This is particularly important for suspension-state measurements, where the effective concentration of material within the probe beam cannot be controlled precisely, and it allows the chiroptical responses of independently prepared batches to be compared directly. The seeded (S)-1-Cd and (R)-1-Cd crystals promoted the formation of MOFs enriched in the corresponding enantiomer, confirming that secondary nucleation can strongly influence chiral selectivity during MOF growth.

The smaller gabs values obtained in (sca)-1-Cd from unseeded synthesis are likely due to spontaneous secondary nucleation. Once the first crystal nucleates from the racemic solution, it can act as an autocatalytic chiral template, directing the formation of subsequent crystals with matching chirality. As MOF crystallization involves dynamic processes of formation, dissolution, and reorganization before reaching thermodynamic stability, enantiomeric clusters not aligned with the seed crystal are likely to be suppressed. Therefore, the presence of even a small enantiomeric excess, whether random or introduced, can bias the entire crystallization pathway making it difficult to obtain a truly racemic MOF product from a racemic precursor.

We further investigated the origin of chiral induction during MOF formation by synthesizing scalemic MOFs from ligand mixtures with a 3 : 1 ratio of (S)-L to (R)-L, and vice versa and analysing the resulting materials by CD spectroscopy (Fig. S16). As expected, the gabs values of these MOFs were smaller than those observed in MOFs synthesized using seeding with enantiopure crystals. This suggests that while an enantiomeric excess in the ligand can bias the chirality of the final product, crystal seeding with an enantiopure MOF provides a more effective and directed chiral induction highlighting the dominant role of templating via secondary nucleation during crystallization.

Photophysical properties

The photophysical properties of (S)-1-Cd, (R)-1-Cd and (sca)-1-Cd were collected in ethanol. The absorption measurements showed that the suspension only absorbed in the UV region with maximum absorption at 240 nm and 300 nm (Fig. S14). For fluorescence measurements, the excitation wavelength at 240 nm was chosen as it yields the highest emission signal at 390 nm (Fig. S15).

Fluorescence response and enantioselective experiments toward aspartic dimethyl ester

From our previous work, we found that a Cd(ii) H8-BINOL-based MOF exhibited a strong response toward aspartic acid dimethyl ester (Asp-diMe) with outstanding enantioselectivity.16 Hence, we investigated the response of (S)-1-Cd, (R)-1-Cd and (sca)-1-Cd towards Asp-diMe.

The fluorescence spectra were measured by adding (R)- or (S)-Asp-diMe to a suspension containing either (S)-1-Cd, (R)-1-Cd or (sca)-1-Cd. The addition of Asp-diMe resulted in fluorescence quenching with distinct differences in quenching strength (Fig. 3). Fluorescence titration of either (S)-1-Cd, (R)-1-Cd or (sca)-1-Cd with Asp-diMe were additionally conducted to study the enantioselectivity. The titrations were performed by adding Asp-diMe into the suspension of (S)-1-Cd, (R)-1-Cd or (sca)-1-Cd in ethanol. The fluorescence change over the quencher concentration was plotted according to the Stern–Volmer equation:32I0/I = KSV[Q] + 1 (where I is the intensity of fluorescence after adding Asp-diMe; I0 is fluorescence signal of (S)-1-Cd, (R)-1-Cd or (sca)-1-Cd; Ksv is the Stern–Volmer constant; and [Q] is the concentration of (Asp-diMe)). The KSV constant represents the relative quencher strength in the experiment. The corrected relative intensities (I0(corr)/I(corr)) were used in the Stern–Volmer plot obtained by combining the corrections for the inner filter effect33 and dilution.

Fig. 3. The fluorescence spectra (λex = 240 nm) in ethanol of (a) (S)-1-Cd and (b) (R)-1-Cd (0.2 g L−1) with enantiomers of Asp-diMe (400 µM). Stern–Volmer plots of (c) (S)-1-Cd and (d) (R)-1-Cd (0.2 g L−1) with the enantiomers of Asp-diMe.

Fig. 3

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The Stern–Volmer analysis showed that both (S)-1-Cd or (R)-1-Cd exhibited an enantioselective fluorescence response toward Asp-diMe with (L)-Asp-diMe quenching more effectively than (D)-Asp-diMe. The enantioselectivity was approximated using the enantioselective ratio (er) calculated by dividing the higher KSV by the lower KSV. The er values of (S)-1-Cd and (R)-1-Cd with Asp-diMe were 4.26 and 2.00 respectively, with a limit of detection (LOD) calculated for (L)-Asp-diMe and (D)-Asp-diMe at 24.22, 36.85 µM for (S)-1-Cd and 22.42, 31.52 µM for (R)-1-Cd respectively. The values demonstrate the presence of enantioselectivity within both enantiomers of the MOF.

An intriguing note is that both (S)-1-Cd or (R)-1-Cd exhibit non-inversion of enantioselectivity toward (L)-Asp-diMe which is a unique property of H8-BINOL when reacting with amino acids. We hypothesized that if both enantiomers show similar enantioselectivity, a racemic mixture of these enantiomers should exhibit overall enantioselectivity, as the chiral effects will not cancel each other out.

Fluorescence response and enantioselectivity of (sca)-1-Cd toward Asp-diMe

The fluorescence quenching properties of (sca)-1-Cd were investigated through the addition of each individual enantiomer of Asp-diMe. (L)-Asp-diMe quenched the fluorescence signal of (sca)-1-Cd more effectively than (D)-Asp-diMe (Fig. 4a). A Stern–Volmer plot of (sca)-1-Cd with Asp-diMe was constructed to quantify the enantioselectivity of the system (Fig. 4b). The results showed that, even though (sca)-1-Cd is a scalemic mixture, it possesses enantioselective properties with an er value of 2.11, with a limit of detection (LOD) calculated toward (L)-Asp-diMe of 28.78 µM and (D)-Asp-diMe of 35.15 µM. Enantioselectivity in this form has not been reported elsewhere and is an extraordinary phenomenon. Typically, the enantiomers would act in opposition, cancelling out the overall signal.

Fig. 4. (a) The fluorescence spectrum of (sca)-1-Cd (λex = 240 nm, 0.2 g L−1) with (L)-Asp-diMe or (D)-Asp-diMe (667 µM) (b) Stern–Volmer plot of (sca)-1-Cd (0.2 g L−1) with either (L)-Asp-diMe or (D)-Asp-diMe.

Fig. 4

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Enantiomeric excess experiments

Enantiomeric excess (ee) is used to evaluate the accuracy of a chiral sensor. In this experiment, the ratio of (S)- and (R)-Asp-diMe was varied to observe the discrimination of the sensor at different ee's. A calibration curve was constructed by measuring (S)-1-Cd, (R)-1-Cd or (sca)-1-Cd with five different ratios of Asp-diMe, maintaining a total analyte concentration of 182 µM. Each ratio was repeated three times, and the standard errors were calculated (Fig. 5). The calibration plots demonstrated that (S)-1-Cd, (R)-1-Cd or (sca)-1-Cd exhibited similar trends in enantioselective detection of the enantiomeric mixture, suggesting that (sca)-1-Cd can effectively function as an enantioselective sensor.

Fig. 5. Enantioselective calibration curves of (a) (S)-1-Cd and (b) (R)-1-Cd (c) (sca)-1-Cd with racemic mixtures of Asp-diMe (182 µM), at various enantiomeric excess (ee) ratios with respect to (L)-Asp-diMe ((λex) = 240 nm).

Fig. 5

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(S)-1-Cd, with an er of 4.26 is comparable to established enantioselective frameworks (Table 1). (sca)-1-Cd (er = 2.11) and (R)-1-Cd (er = 2.00) display more modest discrimination, but remain firmly within the range reported for enantiopure MOF sensors, comparable to systems such as UiO-66-C15 (2.01), [Zn3(S-L1)(tma)2(DMF)3]·2DMF12 (2.23), IRMOF-74-II-Mg-C-Tb14 (2.40) and MIL-53-C2 15 (2.51). Notably, LOD values are not reported for the majority of the systems listed, which limits direct comparison on this basis.

Table 1. Reported enantioselective turn-off fluorescence sensor MOFs with enantioselective ratios (er), limits of detection (LOD) and linear ranges where two LOD values correspond to the (l)- and (d)- enantiomer of the analyte. N/A denotes a value that was not reported, and ≤ indicates that no lower bound to the linear range was determined.

Frameworks Chiral analytes er LOD (µM) Linearity range (µM) Ref.
[Cd((S)-L)3(bdc)2] Aspartic acid dimethyl ester 14.97 N/A ≤667 16
Mandelic acid 2.70 N/A
N/CDs@Eu-MOF Lysine 13.0 0.12 (L) N/A (D) 0.4–200 34
[Cd((R)-L)3(bdc)2] Aspartic acid dimethyl ester 12.41 N/A ≤667 16
Mandelic acid 4.43 N/A
M-HMOF-5 Phenylalanine 5.85 N/A ≤800 35
Mandelic acid 2.71 N/A ≤1000
[Cd2(D-L)2(bibt)2] Glutamic acid 4.29 2.68 (L) 9–25 36
0.37 (D)
Cd2(S-L)2(DMF)2(H2O)2·DMF ((S)-1-Cd) Aspartic acid dimethyl ester 4.26 24.22 (L) 100–400 This work
36.85 (D)
[Zn2(S-L2)(D-cam)2]·0.5DMF·10H2O (1-OH) Mosher's acid 3.92 N/A 200–600 11
[Zn2(S-L1)(D-cam)2]·4.9DMF·2.8H2O (1-OEt) Mosher's acid
3.72 N/A
[Cd(L)(4,4′-bpy)]·DMA·5H2O Penicillamine 3.60 2.1 (L) 20–167 13
0.9 (D)
MIL-53-C1 Quinine/quinidine 3.26 N/A 500–800 15
Eu-MOF-DCam Mandelic acid 2.56 N/A ≤43 37
MIL-53-C2 Quinine/quinidine 2.51 N/A 500–800 15
IRMOF-74-II-Mg-C-Tb 1-Phenylethanol 2.40 N/A 7000–13000 14
[Zn3(S-L1)(tma)2(DMF)3]·2DMF Mosher's acid 2.23 N/A ≤450 12
Cd2(L)2(DMF)2(H2O)2·DMF ((sca)-1-Cd) Aspartic acid dimethyl ester 2.11 28.78 (L) 100–700 This work
35.15 (D)
UiO-66-C Quinine/quinidine 2.01 N/A 300–500 15
Cd2(R-L)2(DMF)2(H2O)2·DMF ((R)-1-Cd) Aspartic acid dimethyl ester 2.00 22.42 (L) 100–400 This work
31.52 (D)
Zn-L-OEt Hydrobenzoin 1.62 N/A ≤1200 38
Zn-L-OH Hydrobenzoin 1.22 N/A
Cd-L-OEt Hydrobenzoin 1.22 N/A
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The significance of these values lies less in their enantioselectivity than in how the materials are obtained. Every previously reported framework in Table 1 requires an enantiopure chiral component, and therefore inherits the cost and synthetic difficulty associated with obtaining the enantiomerically pure precursors. (sca)-1-Cd is prepared directly from racemic L yet delivers enantioselectivity comparable to several of these systems, demonstrating that useful chiral recognition need not depend on access to enantiopure building blocks. We note that higher enantioselectivities have been achieved with H8-BINOL-based frameworks of different topology,16 indicating that the ligand platform itself is capable of considerably greater discrimination; the contribution of the present work is to show that such discrimination can be retained in a non-enantiopure material.

Computational results

Computational calculations were performed to investigate the interaction of Asp-diMe within the pores of both (S)-1-Cd and (R)-1-Cd and elucidate the origin of the chiral non-inversion. Two distinct types of cavities are present in both (S)-1-Cd and (R)-1-Cd, as illustrated in Fig. S21b and S21c. We begin by investigating the interactions between the guests and the frameworks when DMF molecules remain coordinated at the Cd(ii) sites. Although both the channels and the cavities can host guest molecules, DMF molecules densely occupy the channels, thus making the incorporation of Asp-diMe guests sterically hindered. Therefore, the structural optimization search for the adsorption of (L) and (D)-Asp-diMe in the presence of DMF molecules was focused on the cavities.

Both Asp-diMe enantiomers bind favourably within the cavities of both MOFs, with (L)-Asp-diMe (ΔEads = −12.6 kcal mol−1 in (S)-1-Cd and −18.3 kcal mol−1 in (R)-1-Cd) consistently binding more strongly than (D)-Asp-diMe (ΔEads = −9.9 kcal mol−1 in (S)-1-Cd and −9.1 kcal mol−1 in (R)-1-Cd). To understand the origin of the enantioselectivity, radial distribution functions (RDF) analysis was used to identify the dominant guest-MOF interactions. For (S)-1-Cd, the CH(H)⋯OMOF interaction appears significant for (L)-Asp-diMe with a peak at 2.7 Å, whereas no comparable short-range peak is observed for (D)-Asp-diMe (RDF peak at 4.7 Å). For (R)-1-Cd, both the –CH(H)⋯OMOF RDF peak (2.5 Å for (L)- and 3.2 Å for (D)-), and the NH2(N)⋯HMOF hydrogen-bond RDF peak (2.3 Å for (L)- and 3.0 Å for (D)-) occur at shorter distances for (L)-Asp-diMe, consistent with its more favourable interaction energy. The different binding modes of the Asp-diMe guests in the two frameworks can be traced to the orientation of the Cd(ii)-coordinated DMF molecules within the pocket-like cavities (Fig. 6e and f). In (S)-1-Cd, the methyl group of Cd(ii) bound DMF points toward the centre of the pore, thus reducing the accessible volume near the MOF carboxylate sites and preventing their interaction with the guests. In contrast, in (R)-1-Cd the coordinated DMF lies close to the cavity wall, allowing strong –NH2(H)⋯OMOF hydrogen bonds to form for (L)-Asp-diMe which explains its stronger adsorption in (R)-1-Cdvs.(S)-1-Cd.

Fig. 6. The radial distribution functions (RDFs) for the following MOF-guest complexes: (a) (S)-1-Cd⋯(L)-Asp-diMe and (b) (S)-1-Cd⋯(D)-Asp-diMe, (c) (R)-1-Cd⋯(L)-Asp-diMe and (d) (R)-1-Cd⋯(D)-Asp-diMe. Asp-diMe guests were placed in the pocket-like cavities of the frameworks in the presence of DMF. The top view of the representative geometry and the local environment of the pocket-like cavity are shown for (L)-Asp-diMe interacting with (e) (S)-1-Cd and (f) (R)-1-Cd. Cadmium, oxygen, nitrogen, carbon and hydrogen atoms are represented by the purple, red, blue, grey, and white sticks/spheres, respectively; the pore-defining ring structures and DMF molecules are highlighted in blue and purple, respectively.

Fig. 6

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To account for the fact that coordinated solvent molecules may compete for metal sites, we computed the adsorption energy associated with Asp-diMe coordinating to these sites through its amine and ester groups upon DMF removal (eqn (4)) and DMF displacement (eqn (5)) in the channels and cavities (Fig. 7). As previously discussed, this is especially critical for the channels where the guest cannot co-adsorb with DMF due to steric hindrance. Although the primary coordination motifs are similar, both guests consistently exhibit a higher adsorption affinity for the channels than for the cavities (Fig. 7a). This preference reflects the more polar environment in the channels, where nearby carboxylate oxygens provide additional opportunities for stabilizing interactions (Fig. 7b and c). In contrast, the cavities are lined with linker rings (Fig. 7d and e), which establish weaker interactions and impose steric constraints.

Fig. 7. The (L) and (D)-Asp-diMe (a) direct adsorption energies in the absence of coordinated DMF (Eads) and DMF displacement energies (Edisp) in the pocket-like cavities and channels of (S) and (R)-1-Cd. Representative adsorption geometries for (S)-1-Cd showing (b) (L)-Asp-diMe and (c) (D)-Asp-diMe in the channels, and (d) (L)-Asp-diMe and (e) (D)-Asp-diMe in the pocket-like cavities. Cadmium, oxygen, nitrogen, carbon, and hydrogen atoms are shown in purple, red, blue, grey, and white, respectively. The intermolecular bonds are represented by the black dotted lines while the repulsive interactions are represented by the purple dotted lines.

Fig. 7

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Across both pore types and MOFs, the adsorption energies consistently favour (L)-Asp-diMe over (D)-Asp-diMe. This enantioselectivity can be explained by the stereochemical fit upon coordination. In the hexagonal channel (Fig. 7b and c), when the amine binds to the metal sites, the –CH2 group forms –CH(H)⋯OMOF interactions with carboxylate oxygen atoms. In addition, (L)-Asp-diMe can orient its ester group parallel to the framework aromatic rings and carboxylate oxygen atoms, while the stereocenter hydrogen points away from the framework hydrogens; together these features reduce repulsion compared to (D)-Asp-diMe. In the pocket-like cavities (Fig. 7d and e), (L)-Asp-diMe gains an additional stabilizing interaction between the ester group and a nearby Cd atom, which is not observed in the case of (D)-Asp-diMe. The computed displacement energies (Fig. 7a) generally follow similar trends but displacing coordinated DMF to adsorb the guest is energetically more costly for the channels. This is easily explained given that accommodating one Asp-diMe requires the removal of one DMF molecule from the cavities and two from the channels.

PXRD (Fig. S20a) and 1H NMR (Fig. S20b) experiments on (sca)-1-Cd after treatment with (L)-Asp-diMe indicate that a small fraction of the ligand is released into solution during the sensing experiment suggesting that Asp-diMe interacts directly with the framework rather than solely occupying the pores. This behaviour supports the computational results, which show that Asp-diMe could coordinate to the Cd(ii) centres through its amine and ester groups and can displace coordinated DMF.

Overall, we consistently find that both (R)-1-Cd and (S)-1-Cd preferentially adsorb (L)-Asp-diMe across the different pores and adsorption configurations. This result is in strong agreement with our experimental observations showing (L)-Asp-diMe quenching more effectively than (D)-Asp-diMe.

Conclusions

Cd(ii) H8-BINOL MOFs (S)-1-Cd, (R)-1-Cd and (sca)-1-Cd were successfully synthesized, consisting of binuclear Cd(ii) nodes linked by H8-BINOL ligands to form a two-dimensional structure. Enantioselective fluorescence sensing experiments using aspartic acid dimethyl ester (Asp-diMe) revealed that both (S)-1-Cd and (R)-1-Cd exhibited chiral non-inversion, yielding er values of 4.26 and 2.00, respectively. Remarkably, (sca)-1-Cd also demonstrated enantioselective recognition of Asp-diMe, with an er of 2.11. This provides a compelling proof-of-concept that, when a chiral sensor displays non-inversion enantioselectivity, the chiral effects do not cancel in the racemic form enabling it to retain functional enantioselectivity. Furthermore, (sca)-1-Cd detected varying ratios of Asp-diMe enantiomers, reinforcing its utility as a cost-effective enantioselective sensor synthesized from racemic ligands. This finding highlights a promising alternative to the use of enantiopure systems, which are often expensive and synthetically demanding.

Importantly, we identified a significant synthetic challenge in obtaining a truly racemic MOF from racemic ligands. Circular dichroism measurements of MOFs synthesized from (rac)-L consistently showed slight enantiomeric excesses. The slight enantiomeric excesses are due to the secondary crystal nucleation, an autocatalytic templating process wherein the first-formed crystal promotes the growth of subsequent crystals with the same handedness, leading to chiral amplification even from racemic starting materials. Seeding the crystallization with a pure enantiomer of 1-Cd was shown to significantly induce the chirality of the resulting MOF, confirming the templating effect of secondary nucleation. Chiral amplification through secondary nucleation is well established for molecular conglomerates, and its extension to framework materials offers a simple and inexpensive route to controlling the handedness of porous solids without recourse to enantiopure precursors with potential application in enantioselective separation, asymmetric catalysis, and circularly polarised luminescent materials.

Our computational results give insights into the origin of the observed enantioselectivity. When DMF remains coordinated to Cd(ii), adsorption is effectively confined to the pocket-like cavities because the hexagonal channels are sterically crowded by DMF molecules. Under this condition, the preference for (L)-Asp-diMe in (S)-1-Cd is mainly associated with favourable –CH(H) ⋯ OMOF interactions that are not observed for (D)-Asp-diMe. In (R)-1-Cd, the coordinated DMF orientation exposes the framework carboxylate sites, allowing (L)-Asp-diMe to form closer contact through –NH2(N)⋯HMOF and –CH(H)⋯OMOF interactions. After DMF removal, the channels provide a more favourable binding environment than the cavities for direct adsorption of Asp-diMe at the Cd(ii) open metal sites. In the channels, the enantioselectivity for (L)-Asp-diMe is again governed by additional –CH(H)⋯OMOF interactions. In the cavities, (L)-Asp-diMe is further stabilized by an interaction between its ester group and a nearby Cd(ii) site. These results indicate that framework enantioselectivity is governed by the interplay between the chiral pore environment and the solvent controlled accessibility of open metal sites.

Beyond this particular system, the broader significance of this work lies in the combination of chiral ligand design with predictive computation, which constitutes a transferable platform rather than a single material. The recognition motifs identified here, coordination of the guest amine to open metal sites, supported by –CH(H)⋯OMOF and –NH2(N)⋯HMOF contacts are common to amino acids and their derivatives, amino alcohols, and a broad range of pharmaceutical scaffolds bearing amine or hydroxyl functionality, indicating that the same recognition chemistry is applicable to these analyte classes.

Together, these results demonstrate that MOFs with non-inversion enantioselectivity can be used in non-pure enantiomer form for chiral sensing. Future work will focus on elucidating the mechanistic origins of this behaviour and expanding this strategy to other chiral analytes and MOF sensors. While circular dichroism has only been used in this study for the characterisation of 1-Cd, it could also serve as a powerful spectroscopic tool for chiroptical sensing as CD can directly probe the chirality of a system.

Experimental

General experimental

All analytes were obtained from commercial sources: Sigma-Aldrich and Combi-Block. All the reactants used in this work were purchased from Combi-Blocks. Fourier Transform Infrared (FT-IR) spectra were measured on an ATR Bruker Alpha spectrometer between 4000–400 cm−1 with 4 cm−1 resolution and 32 scans. Thermogravimetric analysis (TGA) was conducted on a PerkinElmer TGA 8000 instrument using ceramic crucibles as sample holders under high purity nitrogen. The TGA analysis involved heating the sample up to 500 °C with a temperature increment of 10 °C min−1. PXRD data was collected on a Rigaku Oxford Diffraction Synergy-S diffractometer employing CuKα at λ = 1.5418 Å. The samples were ground into immersion oil and the resultant slurry was mounted on a cryo-loop. PXRD patterns from single crystal structures were calculated using Mercury 2024.3.1. Absorption and emission experiments were performed with quartz cuvettes; UV-vis absorption spectra were recorded on an Agilent Technologies Cary 60 UV-vis Spectrophotometer. Samples were dispersed in EtOH (0.125 g L−1) by sonication before the measurement was collected in a 1 cm quartz cuvette. Absorbance, A, was corrected to account for Mie and Rayleigh scattering contributions, represented by constants M and R, respectively, in eqn (1).39Araw is the measured absorbance.

graphic file with name d6sc04635e-t1.webp 1

CD measurements were taken using a JASCO-1500 spectrophotometer. 0.125 g L−1 in ethanol samples were dispersed and sonicated before collecting measurement in a 1 cm quartz cuvette.

Ligand synthesis

5,5′-[[5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthalene]-2,2′-diylbis(oxymethylene)]bis(1,3-benzenedicarboxylic acid)

(S)-L, (R)-L and (rac)-L. (S), (R) or 1 : 1 ratio of (S) and (R)-5,5′,6,6′,7,7′,8,8′-Octahydro-1,1′-binaphthol (H8-BINOL) (0.600 g, 2.04 mmol) and K2CO3 (1.20 g, 8.64 mmol) were dissolved in acetonitrile (20 mL). 1,3-Dimethyl-5-(bromomethyl)benzene-1,3-dicarboxylate (1.26 g, 4.39 mmol) was then added to the mixture. The reaction was stirred and heated at reflux temperature for 6 hours to yield a brown cloudy suspension. Ethyl acetate (50 mL) was added to the reaction mixture after cooling to room temperature, before the organic layer was washed with water (3 × 70 mL) and brine (70 mL). The organic layer was dried with anhydrous Na2SO4 and evaporated under reduced pressure. The intermediate product (L-Methyl Ester), (S) or (R)- 5,5′-[[5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthalene]-2,2′-diylbis(oxymethylene)]bis(1,3,-benzenedicarboxylic acid, dimethyl ester)) was obtained as pale white powder (1.42 g, 98%). 1H NMR (400 MHz, CDCl3) δ (ppm): 8.49 (s, 2H), 7.95 (s, 4H), 7.08–7.05 (d, 2H), 6.82–6.80 (d, 2H), 5.09–5.01 (q, 4H), 3.90 (s, 12H), 2.80–2.77 (m, 4H), 2.41–2.34 (m, 2H), 2.23–2.16 (m, 2H), 1.77–1.63 (m, 8H).

L-methyl ester (0.500 g, 0.71 mmol) was dissolved in acetone (2.0 mL) added to a solution of NaOH (0.500 g, 12.5 mmol) in MeOH (5.0 mL) and H2O (5.0 mL). The reaction was heated to 80 °C and stirred for 6 hours to yield a light-yellow solution. The solution was cooled in an ice-bath and acidified with 37% HCl until precipitation occurred. The pale powder was collected to yield the product as a pale solid (477 mg, 97%). 1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.30 (s, 2H), 7.97 (s, 4H), 6.96–6.94 (d, 2H), 6.83–6.80 (d, 2H), 5.13 (s, 4H), 2.78–2.62 (m, 4H), 2.29–2.21 (m, 2H), 2.08–2.01 (m, 2H), 1.67–1.52 (m, 8H). 13C{1H} NMR (101 MHz, DMSO-d6) δ (ppm): 166.63, 152.72, 139.44, 135.98, 131.60, 131.47, 129.69, 129.12, 128.72, 125.72, 110.34, 68.13, 28.86, 27.14, 22.83, 22.81.

Metal–organic framework synthesis

(S)-1-Cd, (R)-1-Cd or (sca)-1-Cd. (S)-L, (R)-L or (rac)-L (6.50 mg, 0.01 mmol) and Cd(NO3)2·4H2O (12.3 mg, 0.04 mmol) were placed in a 2 mL glass vial and dissolved in a mixture of DMF (0.5 mL) and water (0.5 mL). The reaction mixture was heated at 70 °C for 2 days to yield colourless needle crystals (4.1 mg, 36.4%). IR (ATR): 3268, 2926, 1651, 1565, 1423, 1382, 1255, 1082, 1027, 935, 779, 732, 673, 439 cm−1.

Seeded MOF crystallization experiment

(rac)-L (6.50 mg, 0.01 mmol) and Cd(NO3)2·4H2O (12.3 mg, 0.04 mmol) were placed in a 2 mL glass vial and dissolved in a mixture of DMF (0.5 mL) and water (0.5 mL). A tiny amount (<1 mg) of (S)-1-Cd or (R)-1-Cd were introduced into the solution using a tip of the spatula. The reaction mixture was heated at 70 °C for 2 days to yield colourless needle crystals (7.4 mg, 49.7%).

Crystallography

SCXRD measurements were performed on the MX1 beamline at the Australian Synchrotron.40 Single crystals were transferred directly from the crystallization medium into immersion oil and cooled down under a stream of nitrogen at 100 K. Crystal structures were solved using the program SHELXT41 and refined using a full matrix least-squares procedure based on F2 (SHELXL),42 within the Olex2 (ref. 43) GUI program. The crystal of (R)-1-Cd was weakly diffracting even with a synchrotron X-ray source.

Fluorescence quenching experiments

Crystals of (S)-1-Cd, (R)-1-Cd, and (sca)-1-Cd were filtered using vacuum filtration, washed with ethanol. 5 mg of crystals were weighed then crushed in a mortar and pestle. The crushed crystals were suspended in ethanol (25.0 mL) to achieve a concentration of 0.2 g L−1. The stock suspensions were stored for two days before beginning the experiments. Chiral analytes, (L) and (D)-Asp-diMe, were prepared as solutions in ethanol at a concentration of 0.002 M.

Fluorescence spectra were recorded on an Agilent Technologies Cary Eclipse Fluorescence Spectrophotometer. The excitation wavelength was set at 240 nm for the fluorescence experiments with a long-pass emission filter at a transmission window of 295–1100 nm to eliminate the second harmonic signal. The emission band of 1-Cd lies entirely within the filter passband and is unaffected. An aliquot of the MOF stock suspension (2.0 mL) was added to a quartz cuvette followed by the addition of chiral analyte in increments of 50 µL until reaching the desired analyte concentration. The MOF suspension was mixed between each addition of the analyte to ensure uniform dispersion and the fluorescence spectra recorded without any further waiting period after shaking.

To verify that adsorption equilibrium is established within this procedure, time-resolved measurements were performed on (S)-1-Cd in kinetic mode, monitoring the emission intensity at 390 nm following three-point analyte additions (300 µL in total) without subsequent agitation. Under these conditions the intensity reached a stable plateau within 8.08 ± 1.50 s for (L)-Asp-diMe and 6.69 ± 1.81 s for (D)-Asp-diMe (Fig. S18). (S)-1-Cd was taken as representative of the series, as (R)-1-Cd and (sca)-1-Cd are isostructural by PXRD and were prepared identically. Suspension stability was assessed by monitoring the emission intensity of each MOF suspension at 390 nm over a stationary period of 120 s, over which the intensity decreased by approximately 5% (Fig. S19a).

The change in suspension volume over the course of the titration was accounted for using an experimentally determined dilution response rather than an assumed volume ratio. A control titration was performed under identical conditions, adding pure ethanol in 50 µL increments to 2.00 mL of the MOF suspension, and the emission intensity at 390 nm recorded at each point (Fig. S17). The measured intensity decreased less steeply than the volume ratio V0/V would predict, as dilution simultaneously reduces scattering and self-absorption by the MOF particles (Fig. S19c).

To account for inner filter effect correction, UV-vis absorption spectra of both analyte enantiomers were recorded over 240–590 nm. No absorbance was detected between 300 and 590 nm; a weak absorbance was observed at the excitation wavelength of 240 nm. Fluorescence intensity ratios were corrected for the inner filter effect according to the expression of Lakowicz:33

FCorr = Fobs × 10[(Aex+Aem)/2] 2

Stern–Volmer analysis was conducted by plotting the fluorescence intensity of the emission peak at 390 nm against the analyte concentration. Corrected relative intensities were obtained by combining the inner filter effect and dilution corrections. As volume correction is unity at the initial volume, they apply only to the denominator of the Stern–Volmer ratio, giving:

graphic file with name d6sc04635e-t2.webp 3

where I(MOF) is the emission intensity of the MOF suspension alone at total volume V and I0(MOF) is the corresponding intensity at the initial volume.

Enantioselective ratios (er) were calculated by comparing the slope of the linear fits representing the Stern–Volmer constant KSV. The limit of detection (LOD) was calculated to be using the formula LOD = 3σ/S, where σ represents the standard deviation of five blank measurements and S represents the slope of the calibration curve.36

Calibration experiments were conducted with racemic samples of the analyte at a total concentration of 182 µM within the cuvette. Linear calibration plots were generated by averaging the fluorescence intensity for each ee value, measured three times. Error bars represent the standard deviation calculated from the fluorescence intensity data using the STDEV function.

Computational methods

Machine-learned interatomic potentials (MLIPs) were employed in this work to study the MOF-guest interactions. MLIPs offer an excellent balance for accuracy and computation efficiency when compared to periodic density functional theory (DFT) and classical force field molecular dynamics.44 We have employed MLIPs based on the Message Passing Atomic Cluster Expansion (MACE),45 specifically the MACE-MPA-0 medium sized foundation model,46 which was trained on the Materials Project Trajectories (MPtrj)47 and Alexandria48 datasets. This model has demonstrated strong performance in predicting guest adsorption behaviour, stable geometries and mechanical properties in MOFs.49,50 All MLIP-based calculations were performed using the Atomic Simulation Environments (ASE)51 coupled to the MACE calculator. Careful benchmarking must be carried out prior to the application of MLIP foundation models on specific systems to ensure reliable results. To this end, we generated 240 configurations of MOF-derived cluster models interacting with the guest. We ensured the configurations captured the main interactions relevant to this system (Fig. S21). The use of cluster models instead of a periodic structure was necessary due to the very large size of the experimental unit cell. We calculated reference energies for these configurations using DFT. For each system, relative energies were defined with respect to the most stable structure, and the difference between DFT and MLIP relative energies were then evaluated. We found that the mean absolute error in relative energies for the MLIP calculations is within 0.7 eV compared with DFT (Fig. S21). On this basis, the model is expected to provide a valid estimation for the MOF–guest interactions in this system.

The DFT simulations to generate the benchmarking data were computed using the Vienna ab initio Simulation Package (VASP)52–56 with the PBE exchange–correlation functional and a Hubbard correction (PBE+U),57,58 together with Grimme's D3 dispersion correction.59 The Hubbard correction was applied using the Dudarev formalism60 with an effective value of Ueff = 3.0 eV for Cd 4d states.60 Core–valence interactions were treated using the projector-augmented-wave (PAW)56 method as implemented in VASP. The valence electronic wavefunctions (4d105s2 for Cd; 2s22p4 for O; 2s22p2 for C; 2s22p3 for N, and 1 s1 for H atoms) were expanded on a plane wave basis with a kinetic energy cut-off of 520 eV. Brillouin zone sampling employed Γ-centred sampling (1 × 1 × 1 k-point grid). Energy self-consistency was converged to 1 × 10−5 eV.

The validated MLIP model was used to simulate the full MOF unit cell (lattice parameters of 10.17 × 21.88 × 42.23 Å3) containing the guest molecules with periodic boundary conditions. As a first step, we performed geometry optimizations with the limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) optimizer61 until the maximum residual force on each atom was below 0.01 eV Å−1. Based on these geometries, we calculated MOF-guest interaction energies. These geometries were then also used as starting point for molecular dynamics (MD) simulations to derive RDFs. These simulations were performed at 300 K with a time step of 1 fs for 50 ps equilibration followed by 500 ps production, both under the NVT ensemble. The temperature was controlled using a Langevin thermostat, and the equations of motion were integrated using the velocity Verlet algorithm. The interaction energies and RDFs were computed for both enantiomers of Asp-diMe within different cavities of (S)-1-Cd and (R)-1-Cd, both with coordinated DMF present and after DMF removal.

The adsorption energy (ΔEads) of the Asp-diMe guests was calculated from the total energy of the adsorption complexes (EMOF+nAsp-diMe) relative to the sum of the energies of the isolated Asp-diMe molecule (EAsp-diMe) and the MOF (EMOF):

ΔEads = EMOF+nAsp-diMe − (nEAsp-diMe + EMOF) 4

ΔEads were computed both in the presence and absence of DMF.

The displacement energy (ΔEdisp) for substitution of n1 DMF molecules by n2Asp-diMe molecules was calculated from the total energy of the resulting complex (EMOF+n2Asp-diMe), the energy of an isolated DMF molecule (EDMF), EAsp-diMe, and the energy of the MOF with DMF in the pores (EMOF+n1DMF):

ΔEdisp = EMOF+n2Asp-diMe + n1EDMF − (n2EAsp-diMe + EMOF+n2DMF) 5

Author contributions

C. H. and P. S. conceptualised the project. P. S. performed the synthesis and characterisation of the ligands and frameworks, including NMR spectroscopy, infrared spectroscopy and single-crystal and powder X-ray crystallography, carried out the photophysical and fluorescence measurements, analysed the resulting data, and wrote the draft of the manuscript. J. Z. performed the computational calculations and analysed the computational data, under the supervision of M. L. J. Z. and M. L. wrote the computational sections. K. M. C. performed the solid-state absorbance and circular dichroism measurements and analysed the corresponding data, under the supervision of G. L. C. H. supervised the project, acquired funding, and reviewed and edited the manuscript.

Conflicts of interest

The authors declare no competing financial interest.

Supplementary Material

SC-OLF-D6SC04635E-s001
SC-OLF-D6SC04635E-s002

Acknowledgments

This work was supported by the Australian Research Council Discovery program (DP250100848). This research was undertaken in part using the MX1 beamline at the Australian Synchrotron, part of ANSTO. This research includes computations using the computational cluster Katana supported by Research Technology Services at UNSW Sydney.

Data availability

CCDC 2471173 (R)-1-Cd and 2471174 (S)-1-Cd contain the supplementary crystallographic data for this paper.62a,b

The data supporting this article have been included as part of the supplementary information (SI). Supplementary information: ligand characterization, PXRD, thermalgravimetric analysis, ATR-FTIR spectra, photophysical data, circular dichroism measurements, and additional computational results. See DOI: https://doi.org/10.1039/d6sc04635e.

References

  1. Evans A. M. Clin. Rheumatol. 2001;20(1):S9–S14. doi: 10.1007/BF03342662. https://dx.doi.org/10.1007/bf03342662 [DOI] [PubMed] [Google Scholar]
  2. Kim J. H. Scialli A. R. Toxicol. Sci. 2011;122:1–6. doi: 10.1093/toxsci/kfr088. [DOI] [PubMed] [Google Scholar]
  3. Zor E. Bingol H. Ersoz M. TrAC, Trends Anal. Chem. 2019;121:115662. doi: 10.1016/j.trac.2019.115662. [DOI] [Google Scholar]
  4. Wu X.-F. Ge Q.-M. Jiang N. Zhao W.-F. Liu M. Cong H. Zhao J.-L. Journal. 2023;11:269. doi: 10.24224/2227-1295-2022-11-10-269-292. [DOI] [Google Scholar]
  5. Penasa R. Licini G. Zonta C. Chem. Soc. Rev. 2025;54:10940–10955. doi: 10.1039/D4CS01202J. [DOI] [PubMed] [Google Scholar]
  6. Al-Sulaimi S. Kushwah R. Abdullah Alsibani M. El Jery A. Aldrdery M. Ashraf G. A. Molecules. 2023:28. doi: 10.3390/molecules28176175. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Sanganyado E. Lu Z. Fu Q. Schlenk D. Gan J. Water Res. 2017;124:527–542. doi: 10.1016/j.watres.2017.08.003. [DOI] [PubMed] [Google Scholar]
  8. Stanley J. K. Brooks B. W. Integr. Environ. Assess. Manage. 2009;5:364–373. doi: 10.1897/IEAM_2008-076.1. [DOI] [PubMed] [Google Scholar]
  9. Alvarez-Rivera G. Bueno M. Ballesteros-Vivas D. Cifuentes A. TrAC, Trends Anal. Chem. 2020;123:115761. doi: 10.1016/j.trac.2019.115761. [DOI] [Google Scholar]
  10. Hao C. Molecules. 2024;29:1106. doi: 10.3390/molecules29051106. [DOI] [Google Scholar]
  11. Thoonen S. Siripanich P. Hua L. Tay H. M. Ramkissoon P. Smith T. A. Lessio M. Hua C. Inorg. Chem. Front. 2024;11(13):3877–3888. doi: 10.1039/D4QI00760C. [DOI] [Google Scholar]
  12. Thoonen S. Tay H. M. Hua C. Chem. Commun. 2022;58:4512–4515. doi: 10.1039/D1CC06872E. [DOI] [PubMed] [Google Scholar]
  13. Zhang Q. Lei M. Kong F. Yang Y. Chem. Commun. 2018;54:10901–10904. doi: 10.1039/C8CC06274A. [DOI] [PubMed] [Google Scholar]
  14. Han Z. Wang K. Min H. Xu J. Shi W. Cheng P. Angew. Chem., Int. Ed. 2022;61:e202204066. doi: 10.1002/anie.202204066. [DOI] [PubMed] [Google Scholar]
  15. Han Z. Wang K. Wang M. Sun T. Xu J. Zhou H.-C. Cheng P. Shi W. Chem. 2023;9:2561–2572. doi: 10.1016/j.chempr.2023.05.004. [DOI] [Google Scholar]
  16. Siripanich P. Zhang J. Lessio M. Hua C. Mater. Chem. Front. 2025;9:2087–2098. doi: 10.1039/D5QM00277J. [DOI] [Google Scholar]
  17. Hall L. A. D'Alessandro D. M. Lakhwani G. Chem. Soc. Rev. 2023;52:3567–3590. doi: 10.1039/D2CS00129B. [DOI] [PubMed] [Google Scholar]
  18. Yusuf V. F. Malek N. I. Kailasa S. K. ACS Omega. 2022;7:44507–44531. doi: 10.1021/acsomega.2c05310. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Zeggai F. z. Ait-Touchente Z. Bachari K. Elaissari A. Chem. Phys. Impact. 2025;10:100864. doi: 10.1016/j.chphi.2025.100864. [DOI] [Google Scholar]
  20. Badaloni E. Cabri W. Ciogli A. Deias R. Gasparrini F. Giorgi F. Vigevani A. Villani C. Anal. Chem. 2007;79:6013–6019. doi: 10.1021/ac070776j. [DOI] [PubMed] [Google Scholar]
  21. Han Z. Wang K.-Y. Wang M. Shi W. Acc. Chem. Res. 2025;58:625–634. doi: 10.1021/acs.accounts.4c00795. [DOI] [PubMed] [Google Scholar]
  22. Han Z. Sun T. Liang R.-R. Guo Y. Yang Y. Wang M. Mao Y. Taylor P. R. Shi W. Wang K.-Y. Zhou H.-C. J. Am. Chem. Soc. 2024;146:15446–15452. doi: 10.1021/jacs.4c03728. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Hubber A. Hua C. Chem. – Eur. J. 2024;30:e202400071. doi: 10.1002/chem.202400071. [DOI] [PubMed] [Google Scholar]
  24. Kshatriya R. ACS Omega. 2023;8:17381–17406. doi: 10.1021/acsomega.2c05535. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Zhang Y. Wang H. Yu H. Sun X. RSC Adv. 2022;12:11967–11973. doi: 10.1039/D2RA00803C. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Wei Z. Tang S. Sun X. Hu Y. Molecules. 2022;27:8470. doi: 10.3390/molecules27238470. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Zeng C. Zhang X. Pu L. ACS Omega. 2018;3:12545–12548. doi: 10.1021/acsomega.8b01870. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Xiao J. Wang X. Xu X. Tian F. Liu Z. Analyst. 2021;146:937–942. doi: 10.1039/D0AN01879A. [DOI] [PubMed] [Google Scholar]
  29. Magna G. Šakarašvili M. Stefanelli M. Giancane G. Bettini S. Valli L. Ustrnul L. Borovkov V. Aav R. Monti D. Di Natale C. Paolesse R. ACS Appl. Mater. Interfaces. 2023;15:30674–30683. doi: 10.1021/acsami.3c05177. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Zhang S. Wang Z. Guo B. Xu J. Polym. Cryst. 2021;4:e10173. doi: 10.1002/pcr2.10173. [DOI] [Google Scholar]
  31. Anwar J. Khan S. Lindfors L. Angew. Chem., Int. Ed. 2015;54:14681–14684. doi: 10.1002/anie.201501216. [DOI] [PubMed] [Google Scholar]
  32. Melavanki R. M. Kusanur R. A. Kadadevaramath J. S. Kulkarni M. V. J. Fluoresc. 2010;20:1175–1180. doi: 10.1007/s10895-010-0664-7. [DOI] [PubMed] [Google Scholar]
  33. Lakowicz J. R., in Principles of Fluorescence Spectroscopy, Springer US, Boston, MA, 1999, pp. 25–61, 10.1007/978-1-4757-3061-6_2 [DOI] [Google Scholar]
  34. Peng L. Xue R. Ren H. Ren B. Wang M. Niu X. Guo H. Yang W. Anal. Chim. Acta. 2025;1376:344617. doi: 10.1016/j.aca.2025.344617. [DOI] [PubMed] [Google Scholar]
  35. Zhao Y.-W. Zhu S.-Y. Li Z.-H. Han X.-J. Zhang N. Pan M. Zhang X.-M. Sci. China Mater. 2026;69:2658–2667. doi: 10.1007/s40843-025-4046-6. [DOI] [Google Scholar]
  36. Li Y. Pan X. Zhang K. Ru J. Zhang Q. J. Mol. Struct. 2026;1359:145429. doi: 10.1016/j.molstruc.2026.145429. [DOI] [Google Scholar]
  37. Wei W. Chang Y. Y. Chen C. Wang H. Qi C. S. Li W. Appl. Organomet. Chem. 2025;39:e70414. doi: 10.1002/aoc.70414. [DOI] [Google Scholar]
  38. Deng C. Liu X. Wang Z. Lin W. Inorg. Chem. 2025;64:2583–2589. doi: 10.1021/acs.inorgchem.4c05575. [DOI] [PubMed] [Google Scholar]
  39. Pilkington T. J. Bignucolo M. W. Ainsworth J. P. Siemann S. Anal. Biochem. 2023;678:115269. doi: 10.1016/j.ab.2023.115269. [DOI] [PubMed] [Google Scholar]
  40. Cowieson N. P. Aragao D. Clift M. Ericsson D. J. Gee C. Harrop S. J. Mudie N. Panjikar S. Price J. R. Riboldi-Tunnicliffe A. Williamson R. Caradoc-Davies T. J. Synchrotron Radiat. 2015;22:187–190. doi: 10.1107/S1600577514021717. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Sheldrick G. Acta Crystallogr., Sect. A. 2015;71:3–8. doi: 10.1107/S2053273314026370. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Sheldrick G. Acta Crystallogr., Sect. C:Struct. Chem. 2015;71:3–8. doi: 10.1107/S2053229614024218. [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. Dolomanov O. V. Bourhis L. J. Gildea R. J. Howard J. A. K. Puschmann H. J. Appl. Crystallogr. 2009;42:339–341. doi: 10.1107/S0021889808042726. [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Wang G. Wang C. Zhang X. Li Z. Zhou J. Sun Z. iScience. 2024:27. doi: 10.1016/j.isci.2024.109673. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Batatia I., Kovacs D. P., Simm G., Ortner C. and Csányi G., arXiv, 2023, preprint arXiv:2206.07697, 10.48550/arXiv.2206.07697 [DOI]
  46. Batatia I. Benner P. Chiang Y. Elena A. M. Kovács D. P. Riebesell J. Advincula X. R. Asta M. Avaylon M. Baldwin W. J. Berger F. Bernstein N. Bhowmik A. Bigi F. Blau S. M. Cărare V. Ceriotti M. Chong S. Darby J. P. De S. Della Pia F. Deringer V. L. Elijošius R. El-Machachi Z. Fako E. Falcioni F. Ferrari A. C. Gardner J. L. A. Gawkowski M. J. Genreith-Schriever A. George J. Goodall R. E. A. Grandel J. Grey C. P. Grigorev P. Han S. Handley W. Heenen H. H. Hermansson K. Ho C. H. Hofmann S. Holm C. Jaafar J. Jakob K. S. Jung H. Kapil V. Kaplan A. D. Karimitari N. Kermode J. R. Kourtis P. Kroupa N. Kullgren J. Kuner M. C. Kuryla D. Liepuoniute G. Lin C. Margraf J. T. Magdău I.-B. Michaelides A. Moore J. H. Naik A. A. Niblett S. P. Norwood S. W. O'Neill N. Ortner C. Persson K. A. Reuter K. Rosen A. S. Rosset L. A. M. Schaaf L. L. Schran C. Shi B. X. Sivonxay E. Stenczel T. K. Sutton C. Svahn V. Swinburne T. D. Tilly J. van der Oord C. Vargas S. Varga-Umbrich E. Vegge T. Vondrák M. Wang Y. Witt W. C. Wolf T. Zills F. Csányi G. J. Chem. Phys. 2025;163:184110. doi: 10.1063/5.0297006. [DOI] [PubMed] [Google Scholar]
  47. Jain A. Ong S. P. Hautier G. Chen W. Richards W. D. Dacek S. Cholia S. Gunter D. Skinner D. Ceder G. Persson K. A. APL Mater. 2013;1:011002. doi: 10.1063/1.4812323. [DOI] [Google Scholar]
  48. Schmidt J. Cerqueira T. F. T. Romero A. H. Loew A. Jäger F. Wang H.-C. Botti S. Marques M. A. L. Mater. Today Phys. 2024;48:101560. doi: 10.1016/j.mtphys.2024.101560. [DOI] [Google Scholar]
  49. Kraß H. Huang J. Moosavi S. M. npj Comput. Mater. 2025;12:4. doi: 10.1038/s41524-025-01872-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  50. Brabson L. M. Medford A. J. Sholl D. S. J. Phys. Chem. C. 2025;129:16811–16825. doi: 10.1021/acs.jpcc.5c04020. [DOI] [PMC free article] [PubMed] [Google Scholar]
  51. Hjorth Larsen A. Jørgen Mortensen J. Blomqvist J. Castelli I. E. Christensen R. Dułak M. Friis J. Groves M. N. Hammer B. Hargus C. Hermes E. D. Jennings P. C. Bjerre Jensen P. Kermode J. Kitchin J. R. Leonhard Kolsbjerg E. Kubal J. Kaasbjerg K. Lysgaard S. Bergmann Maronsson J. Maxson T. Olsen T. Pastewka L. Peterson A. Rostgaard C. Schiøtz J. Schütt O. Strange M. Thygesen K. S. Vegge T. Vilhelmsen L. Walter M. Zeng Z. Jacobsen K. W. J. Phys.:Condens. Matter. 2017;29:273002. doi: 10.1088/1361-648X/aa680e. [DOI] [PubMed] [Google Scholar]
  52. Kresse G. Furthmüller J. Phys. Rev. B:Condens. Matter Mater. Phys. 1996;54:11169–11186. doi: 10.1103/PhysRevB.54.11169. [DOI] [PubMed] [Google Scholar]
  53. Kresse G. Furthmüller J. Comput. Mater. Sci. 1996;6:15–50. doi: 10.1016/0927-0256(96)00008-0. [DOI] [Google Scholar]
  54. Kresse G. Hafner J. Phys. Rev. B:Condens. Matter Mater. Phys. 1994;49:14251–14269. doi: 10.1103/PhysRevB.49.14251. [DOI] [PubMed] [Google Scholar]
  55. Kresse G. Hafner J. Phys. Rev. B:Condens. Matter Mater. Phys. 1993;47:558–561. doi: 10.1103/PhysRevB.47.558. [DOI] [PubMed] [Google Scholar]
  56. Kresse G. Joubert D. Phys. Rev. B:Condens. Matter Mater. Phys. 1999;59:1758–1775. doi: 10.1103/PhysRevB.59.1758. [DOI] [Google Scholar]
  57. Perdew J. P. Burke K. Ernzerhof M. Phys. Rev. Lett. 1996;77:3865–3868. doi: 10.1103/PhysRevLett.77.3865. [DOI] [PubMed] [Google Scholar]
  58. Anisimov V. I. Zaanen J. Andersen O. K. Phys. Rev. B:Condens. Matter Mater. Phys. 1991;44:943–954. doi: 10.1103/PhysRevB.44.943. [DOI] [PubMed] [Google Scholar]
  59. Grimme S. Ehrlich S. Goerigk L. J. Comput. Chem. 2011;32:1456–1465. doi: 10.1002/jcc.21759. [DOI] [PubMed] [Google Scholar]
  60. Dudarev S. L. Botton G. A. Savrasov S. Y. Humphreys C. J. Sutton A. P. Phys. Rev. B. 1998;57:1505–1509. doi: 10.1103/PhysRevB.57.1505. [DOI] [Google Scholar]
  61. Saputro D. R. S. Widyaningsih P. AIP Conf. Proc. 2017;1868:040009. doi: 10.1063/1.4995124. [DOI] [Google Scholar]
  62. (a) CCDC 2471173: Experimental Crystal Structure Determination, 2026, 10.5517/ccdc.csd.cc2nyg8c [DOI]; (b) CCDC 2471174: Experimental Crystal Structure Determination, 2026, 10.5517/ccdc.csd.cc2nyg9d [DOI]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Citations

  1. (a) CCDC 2471173: Experimental Crystal Structure Determination, 2026, 10.5517/ccdc.csd.cc2nyg8c [DOI]
  2. (b) CCDC 2471174: Experimental Crystal Structure Determination, 2026, 10.5517/ccdc.csd.cc2nyg9d [DOI]

Supplementary Materials

SC-OLF-D6SC04635E-s001
SC-OLF-D6SC04635E-s001.cif (830.7KB, cif)
SC-OLF-D6SC04635E-s002
SC-OLF-D6SC04635E-s002.pdf (1.8MB, pdf)

Data Availability Statement

CCDC 2471173 (R)-1-Cd and 2471174 (S)-1-Cd contain the supplementary crystallographic data for this paper.62a,b

The data supporting this article have been included as part of the supplementary information (SI). Supplementary information: ligand characterization, PXRD, thermalgravimetric analysis, ATR-FTIR spectra, photophysical data, circular dichroism measurements, and additional computational results. See DOI: https://doi.org/10.1039/d6sc04635e.

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