Redox-Induced <i>In Situ</i> Growth of MnO₂ with Rich Oxygen Vacancies over Monolithic Copper Foam for Boosting Toluene Combustion

Abstract

Catalytic combustion has been known to be an effective technique in volatile organic compound (VOC) abatement. Developing monolithic catalysts with high activity at low temperatures is vital yet challenging in industrial applications. Herein, monolithic MnO₂-O_v/CF catalysts were fabricated via the <i>in situ</i> growth of K₂CuFe(CN)₆ (CuFePBA, a family of metal-organic frames) over copper foam (CF) followed by a redox-etching route. The as-synthesized monolith MnO₂-O_v-0.04/CF catalyst displays a superior low-temperature activity (T_90% = 215 °C) and robust durability for toluene elimination even in the presence of 5 vol % water. Experimental results reveal that the CuFePBA template not only guides the <i>in situ</i> growth of δ-MnO₂ with high loading over CF but also acts as a source of dopant to create more oxygen vacancies and weaken the strength of the Mn-O bond, which considerably improves the oxygen activation ability of δ-MnO₂ and consequently boosts the low-temperature catalytic activity of the monolith MnO₂-O_v-0.04/CF toward toluene oxidation. In addition, the reaction intermediate and proposed mechanism in the MnO₂-O_v-0.04/CF mediated catalytic oxidation process were investigated. This study provides new insights into the development of highly active monolithic catalysts for the low-temperature oxidation of VOCs.