DFT-Guided Screening and Mechanistic Insights into Metal-Modified Mn/HZSM-5 Catalysts for Low-Temperature Toluene Oxidation

Abstract

A rational design strategy is proposed for developing efficient M-Mn/HZSM-5 catalysts for low-temperature oxidation of toluene. Density functional theory (DFT) calculations were employed to screen suitable metals by evaluating toluene adsorption, O2 activation, and oxygen-vacancy formation on M-Mn/HZSM-5 surfaces, identifying Cu as the optimal promoter. Guided by theoretical predictions, a group of M-Mn/HZSM-5 catalysts were prepared and systematically evaluated. Among them, CuMn/HZSM-5 exhibited the most favorable performance, achieving a T90 of 255 °C with excellent CO2 yield, low activation energy, and outstanding stability and water tolerance. Characterization results revealed that Cu promoted active-species dispersion, raised the proportion of Mn3+ species and surface adsorbed oxygen, and facilitated the migration of lattice oxygen. In situ DRIFTS demonstrated that Cu accelerated intermediate decomposition without altering the intrinsic toluene oxidation pathway. Spearman correlation analysis further indicated that O2 adsorption energy showed the strongest rank correlation with T90, while toluene adsorption energy and oxygen-vacancy formation energy provided useful auxiliary information for screening metal promoters. These results demonstrate the effectiveness of a calculation-guided design strategy, providing a practical guideline for designing high-efficiency zeolite catalysts for VOC elimination.