Homochiral BINOL-Based Metal–Organic Frameworks for Luminescence Sensing of Hydrobenzoin Enantiomers

Luminescent chiral metal–organic frameworks (CMOFs) are promising candidates for the enantioselective sensing of important chiral molecules. Herein, we report the synthesis and characterization of Zn and Cd CMOFs based on 1,1′-bi-2-naphthol (BINOL)-derived 3,3′,6,6′-tetra(benzoic acids), H₄L-OEt and H₄L–OH. Four CMOFs, Zn-L-OEt, Zn-L–OH, Cd-L-OEt, and Cd-L–OH, based on these ligands were crystallographically characterized. Zinc cations form 8-connected (8-c) penta-metallic secondary building units (SBUs), while cadmium cations form 4-c trimetallic SBUs. These SBUs are linked by 4-c L-OEt and L–OH ligands to form noninterpenetrated 4, 8-c 4,8T41 zinc CMOFs (Zn-L-OEt and Zn-L–OH) and 2-fold interpenetrated 4-c diamondoid (dia) cadmium CMOFs (Cd-L-OEt and Cd-L–OH), respectively. At a ligand concentration of 24 μM, H₄L-OEt and H₄L–OH showed negligible luminescent quenching by RR- and SS-hydrobenzoin (HB) enantiomers with Stern–Völmer constants of 29–89 M^–1. In contrast, CMOFs displayed efficient quenching by HB enantiomers with Stern–Völmer constants of 583–1200 M^–1, due to significant HB preconcentration in CMOF channels via favorable host–guest interactions between CMOF frameworks and HB molecules. The CMOFs demonstrated luminescence quenching selectivity for RR-HB over SS-HB, with Zn-L-OEt exhibiting the highest quenching ratio (K_sv(RR)/K_sv(SS)) of 1.624. This work highlights the potential of CMOFs in enantioselective sensing applications.