Modulating Lewis acidity by oxygen vacancies engineering in Ce-doped manganese dioxides to promote permanganate...

The development of efficient and eco-friendly solid catalysts with strong Lewis acid sites for permanganate (KMnO₄) activation is highly desired for pollutant removal. In this study, the oxygen vacancy (O_V) content of cryptomelane-type manganese oxide, was modulated by Ce doping to promote its Lewis acidity. The findings show that incorporating Ce into the framework of MnO₆^- octahedra inhibits the growth of the catalyst to form a completely amorphous structure, with the increase of O_V ratio, especially bulk O_V content. Accordingly, the amount and strength of medium acids, as well as the total acids significantly increase. The increment of O_V content and the synergistic effect between surface and bulk O_V then lead to the faster degradation of sulfadiazine via KMnO₄ activation. The enhanced oxidation potential and electron transfer reactivity of adsorbed KMnO₄ on O_V sites are further confirmed to contribute to the degradation reaction, while the role of reactive intermediate Mn species is insignificant. The system also shows high efficiency for other pollutants treatment, high KMnO₄ utilization, and good adaptability under various conditions. This work demonstrates that O_V engineering of metal oxides is a cost-effective and promising strategy to enhance its Lewis acidity for efficient KMnO₄ activation.