The Importance of Si─ONa─Al Moieties in Fe/ZSM‐5 Zeolite Catalysts for Selective Oxidation of Methane to Acetic Acid

Abstract Selective oxidation of methane to acetic acid with high activity and selectivity remains a significant challenge. Brønsted acid sites (Si─OH─Al) are well‐known for their crucial role in facilitating methane oxidation to acetic acid over zeolite‐based catalysts. Here, we reported that Fe/ZSM‐5‐0.25Na with abundant Si─ONa─Al moieties outperformed Fe/ZSM‐5 (rich in Brønsted acid sites) in methane oxidation to acetic acid using H 2 O 2 in the presence of CO. The Fe/ZSM‐5‐0.25Na yielded 144.1 µmol of oxygenated products, achieving an acetic acid selectivity of 81.8% at 50 °C for 2.0 h. These results surpass the performance of the Fe/ZSM‐5 catalyst, which produced 131.4 µmol of oxygenated products with an acetic acid selectivity of 58.4%. Spectroscopic characterizations and mechanistic studies revealed that the Si─ONa─Al moieties in Fe/ZSM‐5‐0.25Na facilitated electron donation to iron species, forming electron‐rich iron sites. These electron‐rich iron species promoted CO insertion and enhanced the formation of acetic acid through carbon–carbon coupling of methane and CO.