Fe binuclear sites convert methane to acetic acid with ultrahigh selectivity

•Fe/ZSM-5 converted methane to CH3COOH with ultrahigh selectivity •[Fe(III)–(μO)2–Fe(III)–(OH)2] was suggested to be the active site •The direct-coupling pathway of ·CH3, CO∗ and OH∗ favored the formation of CH3COOH The direct conversion of methane to C2 oxygenates with high selectivity under mild conditions has attracted wide attention but still remains a great challenge. Herein, we report the conversion of methane to acetic acid (CH3COOH) with ultrahigh selectivity for oxygenated products by the direct coupling of CH4, CO, and H2O2 over ZSM-5-supported Fe binuclear sites under 30°C. The unexpected ultrahigh selectivity toward CH3COOH was attributed to the unique Fe binuclear site structure of [Fe(III)–(μO)2–Fe(III)–(OH)2], which was evidenced by advanced spectroscopic techniques and density functional theory (DFT) calculations. It was suggested that the lower energy barriers for the direct coupling of methyl radicals (·CH3) and adsorbed CO∗ and OH∗ species to form CH3COOH, compared with the oxidation of CH4 by OH∗ to form CH3OH, benefited the CH3COOH formation. The direct conversion of methane to C2 oxygenates with high selectivity under mild conditions has attracted wide attention but still remains a great challenge. Herein, we report the conversion of methane to acetic acid (CH3COOH) with ultrahigh selectivity for oxygenated products by the direct coupling of CH4, CO, and H2O2 over ZSM-5-supported Fe binuclear sites under 30°C. The unexpected ultrahigh selectivity toward CH3COOH was attributed to the unique Fe binuclear site structure of [Fe(III)–(μO)2–Fe(III)–(OH)2], which was evidenced by advanced spectroscopic techniques and density functional theory (DFT) calculations. It was suggested that the lower energy barriers for the direct coupling of methyl radicals (·CH3) and adsorbed CO∗ and OH∗ species to form CH3COOH, compared with the oxidation of CH4 by OH∗ to form CH3OH, benefited the CH3COOH formation.