Au‐Decorated Nb₂O₅ Featuring Unsaturated Niobium Centers and Photoinduced Oxygen Vacancies for Photocatalytic Oxidative Coupling of Methane to C₂₊ Hydrocarbons

Photocatalytic oxidative coupling of methane (OCM) holds considerable potential for producing value‐added chemicals. However, this technology currently faces two major challenges: low methane conversion and significant overoxidation. Herein, we report a gold (Au) decorated niobium pentoxide (Nb 2 O 5 ) featuring unsaturated Nb centers and photoinduced oxygen vacancies (O V ), which achieved a CH 4 conversion rate of 3.21 mmol g −1 h −1 with a selectivity of ∼98.1% toward C 2+ hydrocarbons ( λ = 320−780 nm, 300 mW cm −2 ), outperforming the selectivity of previously reported photocatalysts. Operando characterizations and theoretical studies demonstrate that the unsaturated Nb centers play a crucial role in promoting methane activation and facilitating the transfer of methyl (*CH 3 ) intermediates to the Au cocatalyst, thereby boosting the C─C coupling pathway while suppressing undesired overoxidation. Concurrently, the photoinduced O V sites enable the timely release of H 2 O from the lattice oxygen, thus enhancing O 2 activation and improving the lattice oxygen looping efficiency. This work provides new insights into the atomically precise design of photocatalysts that deliver both good activity and high selectivity in methane valorization.