Coligand syntheses, crystal structures, luminescence and photocatalytic properties of 2D and 3D Ni(II) coordination polymers based on terephthalic acid and flexible bis(benzimidazole) linkers

Abstract

Two new Ni(II) coordination polymers (CPs) [Ni(TP)(L1)(H2O)]n (1) and [Ni(TP)(L2)]n (2), were synthesized via hydrothermal reaction (H2TP = terephthalic acid, L1 = 1,6-bis(2-methylbenzimidazol-1-yl)hexane, L2 = 1,6-bis(5,6-dimethylbenzimidazol-1-yl)hexane, and structurally characterized by X-ray single crystal diffraction analysis, elemental analyses, thermogravimetric analysis, X-ray powder diffraction and IR spectra. CP 1 exhibits a 2D hcb layer, which is further extended into 3D supramolecular architecture by classical O–H⋯O hydrogen-bonding interactions. CP 2 possesses a 3D 4-connected sra framework. Both CPs possess high thermal stability and promising photocatalytic activities for the degradation of methylene blue (MB) under UV irradiation. The photocatalytic mechanism was investigated by introducing benzoquinone (BQ), the ammonium oxalate (AO), and tert-butyl alcohol (TBA) as superoxide radical (·O2−), hole (h+), and hydroxyl radical (·OH) scavengers, respectively.