Syntheses, structures, photoluminescence and photocatalysis of chiral 3D Cd(ii) frameworks from achiral mixed flexible ligands by spontaneous resolution

Abstract

Unprecedented two homochiral Cd(II) enantiomers [Cd(dtba)(bpp)]_n (1: 1P and 1M) (H₂dtba = 2,2′-dithiodibenzoic acid, bpp = 1,3-bis(4-pyridyl)propane), were obtained by self-assembly with mixed achiral flexible ligands. Single-crystal X-ray diffraction analysis reveals that complexes 1P and 1M crystallize in trigonal space groups P3₁21 and P3₂21, respectively. The compounds are optically active, and their UV spectra in the solid state showed Cotton effects in the opposite directions. Compounds 1P and 1M present the examples of three-interpenetrating chiral frameworks with triangular and quasi-heart-like threefold helical chiral channels, chair-like twofold helical chiral channels and one type of threefold double-helical chain. The 3D metal–organic framework can be regarded as a bcu-type topology with the symbol of 8⁶. The photoluminescent properties of compound 1 have been studied. Remarkably, compound 1 exhibits good photocatalytic activity for degradation of dyes under the simulated sunlight irradiation in the pH = 3 aqueous solution.