Selective catalytic properties determined by the molecular skeleton: Two new isostructural coordination polymers[{M(H2O)5}2(μ-4-bpdh)(oba)]∞(M = Co, Ni)

Two new isostructural metal–organic coordination polymers [{M(H2O)5}2(μ-4-bpdh)(oba)]∞(M = Co, Ni), 1Co and 2Ni, respectively, were constructed from 4-bpdh (2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) and oba (4,4′-oxybis(benzoic acid)) in a MeOH–H2O solvent system. The Co (Ni) ion was located in a hexa-coordinate environment surrounded by five aqua ligands and one 4-bpdh ligand, which bridged two metal centers to form a rod-like structure. Both the Co and Ni coordination polymers can catalyze methyl orange (MO) and malachite green (MG), showing that the unique molecular skeleton determines their properties. Interestingly, different central metal ions of 1Co and 2Ni result in the difference of degradation efficiency. Furthermore, microcrystals of 1Co (2Ni) with different sizes and morphologies were obtained under various conditions. Additionally, a detailed oxidation catalytic mechanism of MO and MG was proposed. These two highly active coordination polymers that are able to selectively degrade organic dyes will be useful in many practical applications.