Enantioselective Recognition and Separation of C₂ Symmetric Substances via Chiral Metal–Organic Frameworks

A promising route toward the enantioselective recognition and separation of racemic molecules is the design of chiral metal–organic frameworks (CMOFs) with high enantioselectivity and stability. Herein, we report porous CMOFs Δ- and Λ-RuEu-MOFs constructed from the D3-symmetry helical chiral Ru(phen)3-derived tricarboxylate ligand and Eu2 units, which can be utilized as adsorbents for the enantioselective recognition and separation of 1,1′-bi-2-naphthol (BINOL) derivatives. Investigation of the circular dichroism enantiodifferentiation between the host and guest suggested that Δ- and Λ-RuEu-MOFs can be employed as chiral sensors to discriminate axial enantiomers due to their diastereomeric host–guest relationship. Density functional theory calculations reveal that chiral recognition is attributed to the distinguishing binding affinities stemming from N···H–O hydrogen bonds and π–π stacking between the host and guest. Moreover, the reticulate structure of Δ- and Λ-RuEu-MOFs can be readily recycled and reused for the successive enantioselective separation of BINOL up to 80% ee.