Structure–Activity Relationships and Catalytic Applications of Manganese-Based Oxides with Different Nanostructures in Multi-Pollutant Gas Treatment

Manganese-based oxides have shown potential in the catalytic treatment of gaseous pollutants, including volatile organic compounds (VOCs), carbon monoxide (CO), and ozone (O3). However, most studies have focused on specific manganese oxides and their performance in treating single pollutants, with limited understanding of behavior across multiple pollutants and under complex conditions relevant to practical applications. This research systematically evaluated the catalytic performance of four manganese-based oxides (MnO2, Mn2O3, Mn3O4, and LaMnO3) under diverse reaction conditions. Results revealed that MnO2 exhibits superior catalytic activity in toluene oxidation (T90 = 207 °C) and CO oxidation due to its well-defined crystal structure and abundant oxygen vacancies. Mn2O3 shows excellent performance in chlorobenzene oxidation (T90 = 328 °C) and ozone decomposition, attributed to the high specific surface area and moderate redox properties. Stability tests highlighted that all catalysts are resistant to H2O and NO poisoning, while Mn2O3 demonstrates enhanced SO2 tolerance by suppressing SO2-to-SO3 conversion and preventing MnSO4 from blocking active sites. Mechanistic analyses indicated that VOCs oxidation is strongly influenced by oxygen vacancies and oxidation states of manganese, while lattice oxygen and redox cycling drive the CO and the O3 reactions.