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

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.