Two-dimensional flexible Ni(II)-based porous coordination polymer showing single-crystal to single-crystal transformation, selective gas adsorption and catalytic properties

Abstract

A novel two dimensional (2D) porous coordination polymer {[Ni3(TBIB)2(BTC)2(H2O)6]·5C2H5OH·9H2O}n (1) [TBIB = 1,3,5-tri(1H-benzo[d]imidazol-1-yl)benzene, H3BTC = 1,3,5-benzenetricarboxylic acid] has been synthesized solvothermally. In 1, layers are stacked in ABAB⋯ fashion by virtue of strong intermolecular hydrogen bonding interactions, to generate an overall 3D supramolecular framework consisting of isolated pockets accommodated solvent molecules inside. These lattice-constituent solvent molecules are replaced by dichloromethane (DCM), after immersing complex 1 in DCM for seven days at room temperature, yielding {[Ni3(TBIB)2(BTC)2(H2O)6]·6CH2Cl2·6H2O}n (2). Arrangement of layers is slightly changed in compound 2 wherein, small pockets are completely absent. Characterization of these two compounds 1 and 2 has been performed employing, single crystal X-ray diffraction, IR spectroscopy, thermogravimetry and elemental analysis. Importantly, complex 1 shows selective sorption of CO2 gas at low temperature and pressure, and simultaneously displays high heterogeneous catalytic activity for Knoevenagel condensation at high temperature.