Subnanometric MoO_x 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 MoO_x 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 MoO_x 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.