Homochiral Porous Metal-Organic Frameworks Constructed from a V-Shaped Alanine Derivative Based on Pyridyl-Dicarboxylate

Three novel, homochiral, porous metal-organic frameworks based on the H₂PDBAla ligand and different divalent cations (Co(II)) and Cu(II)), namely, [M(PDBAla)(bipy)(H₂O)₂]·3H₂O (M = Co 1 and Cu 2), [Cu(PDBAla)(bpea)]·7H₂O (3) (H₂PDBAla = pyridine-2,6-dicarbonyl-bis(l-alanine), bipy = 4,4′-bipyridine, bpea = 1,2-bis(4-pyridyl)ethane), have been synthesized and characterized with the assistance of N-donor ligands. The distinctive H₂PDBAla ligands are coordinated to divalent metal ions by the different coordination modes, forming various helixes in compounds 1-3. Compounds 1 and 2 are isostructural and feature a 2-fold interpenetrating three-dimensional (3D) framework with the cds topological net built by the combination right-handed helical chains and bipy ligands, whereas a 3D framework with the tcj topological net is observed in compound 3, wherein bpea ligands reinforce the 3D framework constructed by right-handed helical chains. Compounds 1 and 3 display high CO₂ absorption capability and superior sorption enthalpies, reflecting the strong affinity of the frameworks for CO₂. Moreover, compound 3 exhibits a small enantioselective separation performance for racemic alcohol.