Synthesis and structural characterization of a flexible metal organic framework {[Ni(dpbz)][Ni(CN)4]}n, dpbz = 1,4-bis(4-pyridyl)benzene) with an unusual Ni–N bond

Abstract

The chartreuse monoclinic Ni-dpbz (Ni(L)[Ni(CN)4], (L = 1,4-Bis(4-pyridyl)benzene, or dpbz) crystal assumes a pillared structure with layers defined by 2-D Ni[Ni(CN)4]n nets and dpbz ligands as pillars, linking between coordinated Ni sites. In addition to the hysteretic adsorption/desorption feature of Ni-dpbz, in half of the parallelepiped-shape space enclosed by the pillars and nets, an additional dpbz ligand was found to link between the open ends of two four-fold Ni sites. This arrangement results in an unusual 5-fold pseudo square-pyramid environment for Ni and a significantly long Ni–N distance of 2.369(4) Å. The presence of disordered dimethyl sulfoxide (DMSO) solvent molecules give rise to the formula of Ni(dpbz)[Ni(CN)4]·½dpbz·0.44DMSO. Sorption isotherms showed flexible behavior during the adsorption and desorption of CO2.