Subnanometric MoOx clusters limit overoxidation during photocatalytic CH4 conversion to oxygenates over TiO2

Direct photocatalytic oxidation of methane to high-value-added oxygenated products remains a great challenge due to the unavoidable overoxidation of target products. Here, we report an efficient and highly selective TiO2 photocatalyst anchored with subnanometric MoOx clusters for photocatalytic methane oxidation to organic oxygenates by oxygen. A high organic oxygenates yield of 3.8 mmol/g with nearly 100% selectivity was achieved after 2 h of light irradiation, resulting in a 13.3% apparent quantum yield at 365 nm. Mechanistic studies reveal a photocatalytic cycle for methane oxidation on the MoOx anchored TiO2, which not only largely inhibits the formation of hydroxyl and superoxide radicals and the overoxidation of oxygenate products but also facilitates the activation of the first carbon-hydrogen bond of methane. This work would promote the rational design of efficient non-noble metal catalysts for direct conversion of methane to high-value-added oxygenates.