Four 3D Cd(II)-Based Metal Organic Hybrids with Different N,N′-Donor Spacers: Syntheses, Characterizations, and Selective Gas Adsorption Properties

Abstract

Four new metal organic frameworks with bivalent cadmium, disodium succinate (Na2suc), and four different N,N′-donor ligands, i.e., {[Cd(L1)(suc)]·(H₂O)3}_n (1), {[Cd(L2)(suc)]·(H₂O)2}_n (2), {[Cd(L3)(suc)]·(H₂O)₄}_n (3), {[Cd₃(L4)3(suc)2(H₂O)2]·(NO₃)2 (H₂O)4}_n (4) [L1 = 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene, L2 = trans 4,4′-azobispyridine, L3 = 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene, L4 = 1, 2-bis(4-pyridyl) ethane and suc = succinate dianion] have been synthesized at room temperature and characterized by single-crystal X-ray diffraction and other physicochemical methods. Structure determination reveals that compounds 1 and 2 show honeycomb-like three-dimensional (3D) architecture with water-filled channels. The dehydrated frameworks of 1 and 2 exhibit hydrogen and carbon dioxide adsorption properties. In compound 3, change of linker (linear to bent) led to the blockage of such regular channels which also affected the porosity and adsorption properties of its dehydrated framework. In 4, the used spacer is linear but the resulting 3D framework contains blocked channels filled with nitrate (NO₃^–) anions and lattice water.