Four MOFs with 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid: syntheses, structures, topologies and properties

Abstract

Four novel metal–organic frameworks, [MnL(DMF)]n (1), [NiL(H2O)2(DMF)]n (2), [Cu2L2(H2O)2]·6H2O·2DMF (3), and Na2(Me2NH2)4[Cd7L10]·9H2O·17Me2NH·2DMF (4), were successfully synthesized in solvothermal conditions using 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid (H2L) as the ligand. The X-ray crystallography analysis reveals that MOF 1 exhibits a 3D framework with sra topology, while MOF 2 shows a 2D network with sql topology though they possess a similar secondary building unit (SBU) [MO6] (M = Mn for 1 and Ni for 2). MOF 3 reveals an unprecedented 4-fold interpenetrated 3D framework with lvt topology constructed from only planar 4-connected nodes ([Cu2(CO2)4] SBUs) with the rigid dicarboxylic acids. MOF 4 features an unique acentric 3D/3D hetero-interpenetrated framework built from two different nodes (4- and 8-connected), different chemical compositions [Cd(CO2)4 and Cd3(CO2)8], and different topology of networks (66 and 424·64) and contains an inorganic 1D chain consisting of a Na+ and three Cd2+ ions. The solid state 113Cd NMR spectrum indicates that 4 has three 6-, 7-, and 8-coordinated Cd2+ ions with chemical shifts at δ −25.3, −41.2 and −83 ppm, respectively. MOF 3 has two kinds of 1D channels with diameters of 11 A and 7 A and exhibits a selective gas adsorption for CO2–N2 and CH4–N2. MOF 4 shows a selective adsorption for cationic dyes and a nonlinear SHG activity (ca. 0.8 times that of urea).