A Series of Metal–Organic Frameworks: Syntheses, Structures and Luminescent Detection, Gas Adsorption, Magnetic Properties

Abstract

Six metal–organic frameworks of [Cd2(L)2(mmpa)2]·6H2O (1), [Mn2(L)2(mmpa)2]·L·2H2O (2), [Zn(L)(NO2 mbda)]·H2O (3), [Cu(L)(NO2 mbda)] (4), [Co3(L)2(BTC)2(H2O)4]·H2O (5), and [Co3(L)2(OBTC)2(H2O)2] (6) were prepared based on different metal salts and the mixed ligands including the N-heterocyclic 1-(4-(1H-imidazol-5-yl)phenyl)-1H-1,2,4-triazole (L) ligand and auxiliary carboxylic acids of 5-methylisophthalic acid (H2 mmpa), 5-nitroisophthalic acid (H2NO2 mbda), trimesuc acid (H3BTC), and 1,2,3-benzenetricarboxylic acid (H3OBTC). MOFs 1 and 2 are isomorphous and isostructural, and both are binodal 4-connected CdS network based on Cd2(COO)2 binuclear secondary building unit (SBU). Compound 3 is a 2D → 3D “polycatenated network” because of its mutual interpenetration between two-dimensional (2D) corrugated (4, 4) layers, while 4 is a sql network on the basis of binuclear [Cu2(COO)2] SBUs. Compound 5 is a trinodal (3, 4)-connected rare nor-3,4-C2/m 3-fold interpenetrated net, while 6 is a 4-connected 3D frl/Ferey ladder net based on L and two isomers of benzenetricarboxylic acids. Photoluminescent properties were determined for the corresponding d10 MOFs. Microporous crystalline material 1 can selectively sense nitroaromatic compounds by fluorescence quenching and show a rare luminescent sensing property for Ag+ ions in H2O solution. Also, the activated microporous material 1 can selectively adsorb CO2 over N2 and undergo H2O vapor adsorption. Furthermore, magnetostructural analyses have also shown that MOFs 2, 4, 5, and 6 consisting of the paramagnetic ions Mn(II), Cu(II)/Co(II), and carboxylate or N-heterocyclic organic molecules exhibit meaningful magnetic-exchange coupling properties.