Decorating titania with ultrasmall UiO-66-H crystallites enables quantitative photocatalytic oxidation of methane to oxygenates

Selective photocatalytic oxidation of methane to liquid oxygenates under ambient conditions remains challenging due to the inert C–H bond and propensity for over-oxidation. Controlling carrier transfer and reactive oxygen species is therefore essential to the selective methane photooxidation. Ultrasmall zirconium metal–organic framework (UiO-66-H) nanocrystals in situ grown on titania form a heterojunction that promotes efficient charge separation and tunes the interfacial band alignment. Comprehensive experiments and characterization reveal that this heterojunction precisely regulates • OH and • OOH generation, enabling controlled, radical-mediated oxidation of methane with a competitive oxygenate yield and nearly 100% selectivity at room temperature using air as an oxidant. In this work, ultrasmall metal–organic framework–semiconductor heterojunctions with a built-in electric field provide an effective route for developing efficient, low-cost photocatalysts for methane chemical valorization under mild, solar-driven conditions.