A novel heterogeneous Co(II)-Fenton-like catalyst for efficient photodegradation by visible light over extended pH

A novel CoII-Fenton-like heterogeneous catalyst, (H3O)2[CoII(phen)(H2O)2]2[MoVI5O15(PO4)2]·4H2O (phen=1,10-phenanthroline, C12N2H8) (1), is synthesized and utilized for photocatalytic degradation of organic dyes and antibiotic in a wide range of pH. The experimental results show that 1 acting as the Fenton-like catalyst with H2O2 exhibits remarkable activity at pH 3–9 under vis-light irradiation and is merited with excellent recyclability and reusability. A variety of analytical methods, including in-situ electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations, are applied to study the mechanism on generation of ·OH and O2·− radicals for photocatalytic degradation. It suggests that, unlike the classical Fenton process involving the redox transformation of the central cations, the generation of ·OH and O2·− radicals is associated with the substitution of the coordinating water molecules at Co(II) by H2O2 and/or OEH−, followed by the light-driven O-O bond cleavage and dissociation The outcomes of this study are striking which overcome the obstacles in the classical FeII-Fenton process, including the slow redox transformation between Fe(II) and Fe(III) and the production of massive iron precipitates especially at elevated pH It opens up new avenues for the development of the high-performance Fenton(-like) catalysts for photocatalytic degradation over extended pH and provides new insight into the related process.