Highly efficient, selective, and stable photocatalytic methane coupling to ethane enabled by lattice oxygen looping

Light-driven oxidative coupling of methane (OCM) for multi-carbon (C₂₊) product evolution is a promising approach toward the sustainable production of value-added chemicals, yet remains challenging due to its low intrinsic activity. Here, we demonstrate the integration of bismuth oxide (BiO_x) and gold (Au) on titanium dioxide (TiO₂) substrate to achieve a high conversion rate, product selectivity, and catalytic durability toward photocatalytic OCM through rational catalytic site engineering. Mechanistic investigations reveal that the lattice oxygen in BiO_x is effectively activated as the localized oxidant to promote methane dissociation, while Au governs the methyl transfer to avoid undesirable overoxidation and promote carbon─carbon coupling. The optimal Au/BiO_x-TiO₂ hybrid delivers a conversion rate of 20.8 millimoles per gram per hour with C₂₊ product selectivity high to 97% in the flow reactor. More specifically, the veritable participation of lattice oxygen during OCM is chemically looped by introduced dioxygen via the Mars-van Krevelen mechanism, endowing superior catalyst stability.