Fe binuclear sites convert methane to acetic acid with ultrahigh selectivity

Abstract

<h2>Summary</h2> 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)–(<i>μ</i>O)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.