Construction of two cobalt based bi-functional metal-organic frameworks for enhancing electrocatalytic water oxidation and photocatalytic disposals of hazardous aromatic dyes

Two novel Co-MOFs constructed from aromatic polycarboxylic acid named {[Co(tib) 2 (bimb) 2 ]·4H 2 O} n (tib = 3-((4-(1H-1,2,4-triazol-1-yl)benzyl)oxy)benzoic acid, bimb = 1,4-bis(imidazole-1-ylmethy) benzene) and {[Co 2 (bipa) 4 (bibp) 6 ]} n (bipa = 2-(4-carboxy-2-nitrophenoxy)-6-nitroterephthalic acid, bibp = 4,4′-bis(imidazolyl) biphenyl), have been synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, powder X-ray diffraction (PXRD), thermogravimetric analysis (TG) as well as electrochemistry. The single-crystal X-ray diffraction analysis indicates that Co-MOF 1 exhibits an uninodal net with a (6 5 ·8) topology, whereas Co-MOF 2 exhibits an uninodal 4-connected framework with a (4 4 ·6 2 ) topology. The electrochemistry studies demonstrate that both of the two Co-MOFs can behave as the efficient electrocatalysts for water oxidation in a mild neutral system at the potential around 1.20 V vs. NHE with comparatively low overpotential ( η ) for Co-MOF 1 and 2 of 337–541 mV vs. NHE. Moreover, the two Co-MOFs also show good photocatalytic degradation capabilities toward MB/MV dyes under UV irradiation, and the mechanism studies demonstrate that the main active species are · OH radicals. Therefore, these bi-functional Co-MOFs materials can be treated as convenient and efficient catalysts for the oxygen evolution reaction and aromatic dyes degradation.