Two copper(i) cyanide coordination polymers modified by semi-rigid bis(benzimidazole) ligands: syntheses, crystal structures, and electrochemical and photocatalytic properties.

Two Cu(i) cyanide coordination polymers (CPs), namely, [Cu2(L1)(CN)2]n (1) and [Cu2(L2)(CN)2]n (2) (L1 = 4,4'-bis(2-methylbenzimidazol-1-ylmethyl)biphenyl, L2 = 4,4'-bis(5,6-dimethylbenzimidazol-1-ylmethyl)biphenyl) were synthesized and structurally characterized by single crystal X-ray diffraction, IR spectroscopy, X-ray powder diffraction and elemental analysis. The cyanide ligands in these CPs are generated in situ from the C-C bond cleavage of acetonitrile under solvothermal conditions, which is environmentally friendly and used conveniently. CP 1 features a three-fold interpenetration 3D framework consisting of Cu10(CN)6(L1)4 rings, which represents the first investigation on introducing bis(benzimidazole) ligands into copper(i) cyanide CPs with ThSi2 topology, while CP 2 exhibits a two-dimensional (6,3) layered structure containing Cu6(CN)4(L2)2 rings. The thermal stabilities, and photoluminescence and electrochemical behavior in the solid state of CPs 1 and 2 have been investigated in detail. Moreover, both CP 1 and CP 2 manifest promising photocatalytic activities (photodegradation efficiency using CP 1 is 90.8% and using CP 2 is 87.2%) for the degradation of methylene blue (MB) under UV light irradiation. A possible photocatalytic mechanism is suggested by introducing t-butyl alcohol (TBA) as a widely used ˙OH scavenger.