Topotactic Transformation of Metal–Organic Frameworks to Graphene-Encapsulated Transition-Metal Nitrides as Efficient Fenton-like Catalysts

Abstract

Innovation in transition-metal nitride (TMN) preparation is highly desired for realization of various functionalities. Herein, series of graphene-encapsulated TMNs (Fe_xMn_6-xCo₄-N@C) with well-controlled morphology have been synthesized through topotactic transformation of metal-organic frameworks in an N₂ atmosphere. The as-synthesized Fe_xMn_6-xCo₄-N@C nanodices were systematically characterized and functionalized as Fenton-like catalysts for catalytic bisphenol A (BPA) oxidation by activation of peroxymonosulfate (PMS). The catalytic performance of Fe_xMn_6-xCo₄-N@C was found to be largely enhanced with increasing Mn content. Theoretical calculations illustrated that the dramatically reduced adsorption energy and facilitated electron transfer for PMS activation catalyzed by Mn₄N are the main factors for the excellent activity. Both sulfate and hydroxyl radicals were identified during the PMS activation, and the BPA degradation pathway mainly through hydroxylation, oxidation, and decarboxylation was investigated. Based on the systematic characterization of the catalyst before and after the reaction, the overall PMS activation mechanism over Fe_xMn_6-xCo₄-N@C was proposed. This study details the insights into versatile TMNs for sustainable remediation by activation of PMS.