Identifying the crucial role of water and chloride for efficient mild oxidation of methane to methanol over a [Cu2(μ-O)]2+-ZSM-5 catalyst.

As-synthesized [Cu 2 (μ-O)]2+-ZSM-5 catalyst shows excellent selectivity to methanol in C1 oxygenates for mild methane oxidation with H 2 O 2 solution, and the reaction mechanism and role of H 2 O and chloride are deeply investigated both experimentally and theoretically. [Display omitted] • A new [Cu 2 (μ-O)]2+-ZSM-5 catalyst was applied for selective mild oxidation of CH 4 to methanol in H 2 O 2 solution. • The reaction mechanism was deeply elucidated both experimentally and theoretically. • Methanol formation via direct dissociation of *CH 3 OOH rather than OH. • The crucial role of water and chloride is intensively investigated. Controllable methane oxidation to methanol is a challenging in catalysis, usually suffering from over-oxidation. We report that a single-metal [Cu 2 (μ-O)]2+-ZSM-5 catalyst can activate methane to methanol with superior high selectivity up to 91.3% in C1 oxygenates and 12.31 mol methanol kg cat -1h−1 by avoiding over-oxidation. Density functional theory (DFT) calculations combined with in situ FT-IR and EPR demonstrated that methanol forms via direct dissociation of strongly adsorbed *CH 3 OOH generated by *CH 3 spontaneously reacting with H 2 O 2 rather than OH. It was found that water plays a crucial role in enhancing methanol formation as other solvents ethanol and acetone show negligible activity. DFT calculations and TPD results confirmed that adsorbed H 2 O* facilitates active site regeneration and accelerate methanol desorption via H migration between H 2 O* and [Cu 2 (μ-OH) 2 ]2+. In addition, the introduction of chloride is favorable for the formation of active [Cu 2 (μ-O)]2+ species owing to a decrease in binding energy between active sites and ZSM-5, and can promote methanol production by weakening the interaction between methanol and active sites by accepting electron from Cu. [ABSTRACT FROM AUTHOR]