Site-Engineered MnGa@In-CHA OXZEO Catalysts for Synergistic Methane and Nitrogen Oxides Abatement

The rapid growth of natural-gas vehicles (NGVs) necessitates robust catalysts for the simultaneous abatement of methane (CH4), nitrogen oxides (NOx), and carbon monoxide (CO) under fluctuating exhaust compositions. We reported a site-engineered MnGa@In-CHA OXZEO catalyst in which indium was confined within an SSZ-13 framework, and Ga2O3 and Mn2O3 phases were uniformly dispersed on its exterior. Mn2O3 markedly enhanced redox capacity, driving NO → NO2 oxidation and lowering the activation energy for C–H bond cleavage in CH4, while Ga2O3 tuned the Brønsted acidity and mediated electron transfer among In, Mn, and Ga centers. In situ DRIFTS studies identified CH4 activation at InO+ sites as the rate-determining step and revealed key intermediates (CH3NO2) that bridged the NOx reduction and CH4/CO oxidation pathways. The optimal Mn1Ga1@In-CHA achieved ≥90% NOx conversion at 390 °C, CH4 conversion at 495 °C, and complete CO oxidation at 300 °C under both lean and rich conditions. It also maintained high activity after 24 h in a humid feed and exhibited stable performance across a wide range of O2 concentrations. These combined features─high activity, selectivity, stability, and adaptability─underscore the promise of MnGa@In-CHA catalysts for NGVs exhaust abatement and offer an important design strategy for multifunctional emission-control materials.