Water-Involved Methane Selective Catalytic Oxidation by Dioxygen over Copper-Zeolites
<p>The selective oxidation of methane to methanol is a dream reaction of direct methane functionalization, which remains a key challenge in catalysis and a hot issue of controversy. Herein, we report the water-involved methane selective catalytic oxidation by dioxygen over copper-zeolites. At 573 K, a state-of-the-art methanol space-time yield of 543 mmol/mol<sub>Cu</sub>/h with methanol selectivity of 91 % is achieved with Cu-CHA catalyst. Temperature-programmed surface reactions with isotope labelling determine water as the dominating oxygen and hydrogen source of hydroxyl in methanol while dioxygen participates in the reaction <a></a><a>through reducing to water</a>. Spectroscopic analyses reveal the fast redox cycle of Cu<sup>2+</sup>-Cu<sup>+</sup>-Cu<sup>2+</sup> during methane selective oxidation, which is closely related to the high catalytic activity of Cu-CHA. Density functional theory calculations suggest that both CuOH monomer and dimer in Cu-CHA can catalyze the selective oxidation of methane to methanol with Cu-OOH as the key reaction intermediate, and meanwhile, various copper sites undergo interconversion under reaction conditions.<br></p>