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

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.

Graphical abstractA two dimensional (2D) flexible coordination polymer of Ni(II) has been solvothermally synthesized, which upon immersing in DCM give rise to a daughter coordination polymer of Ni(II). Compound 1 behaves as a good selective adsorbent for CO2 at low temperature and pressure as well as, an environment-friendly heterogeneous catalyst for Knoevenagel condensation reaction.Figure optionsDownload full-size imageDownload as PowerPoint slide