Characterization and gas adsorption of a novel three-dimensional metal-organic framework (MOF) generated from a new polydentate fluorene-bridged ligand.

Abstract

A polydentate ligand bridged by a fluorene group, namely 9,9-bis(2-hydroxyethyl)-2,7-bis(pyridin-4-yl)fluorene (L), has been prepared under solvothermal conditions in acetonitrile. Crystals of the three-dimensional metal-organic framework (MOF) poly[[[μ3-9,9-bis(2-hydroxyethyl)-2,7-bis(pyridin-4-yl)fluorene-κ3N:N':O]bis(methanol-κO)(μ-sulfato-κ2O:O')nickel(II)] methanol disolvate], {[Ni(SO4)(C27H24N2O2)(CH3OH)]·2CH3OH}n, (I), were obtained by the solvothermal reaction of L and NiSO4 in methanol. The ligand L forms a two-dimensional network in the crystallographic bc plane via two groups of O-H...N hydrogen bonds and neighbouring two-dimensional planes are completely parallel and stack to form a three-dimensional structure. In (I), the NiII ions are linked by sulfate ions through Ni-O bonds to form inorganic chains and these Ni-containing chains are linked into a three-dimensional framework via Ni-O and Ni-N bonds involving the polydentate ligand L. With one of the hydroxy groups of L coordinating to the NiII atom, the torsion angle of the hydroxyethyl group changes from that of the uncoordinated molecule. In addition, the adsorption properties of (I) with carbon dioxide were investigated.