Electron transfer to direct oxidation of aqueous organics by perovskites

The residual of oxidant chemicals in advanced oxidation processes (AOPs) resulted in both economic cost and secondary pollution. Herein, we report a direct oxidation of phenolic pollutants induced by Ca-Mn-O perovskites without using an oxidant. Governed by one-electron transfer process (ETP) from the phenolics to the Ca-Mn-O perovskites, this direct oxidation proceeds in fast reaction kinetics with activation energy of 51.4 kJ/mol, which was comparable with those AOPs-based catalytic systems. Additionally, mineralization and polymerization reactions occurred on the Ca-Mn-O surface and ensured the complete removal of phenolics. The high spin state Mn(III) within Ca-Mn-O structure was the dominant active site for this ETP. The elongated axial Mn(III)–O bonds within the [MnO₆] octahedron facilitated the acceptance of the electrons from the phenolics and thus promoted the initiation of the direct oxidation process. Mn(III) in the high spin state can also activate dissolved O₂ to produce singlet oxygen (¹O₂) for a fast removal of phenolics. The mixed Mn(III)/Mn(IV) within Ca-Mn-O accelerated the ETP by enhancing the electrical conductivity. This efficient Ca-Mn-O-induced ETP for removal of organic contaminants casts off the dependence on external chemical and energy inputs and provides a sustainable approach for transforming the toxic organic pollutants into value-added polymers.