Boosting Water Vapor‐Assisted Methane Photooxidation Over S‐Scheme MIL‐125‐NH ₂ (Ti)/WO ₃ Heterojunction Photocatalysts

ABSTRACT The photocatalytic conversion of methane (CH 4 ) into value‐added oxygenates without overoxidation under mild conditions remains a significant challenge in heterogeneous catalysis. Here, we rationally designed a series of S‐scheme MIL‐125‐NH 2 (Ti)/WO 3 ‐x (MW‐x) heterostructures via electrostatic self‐assembly for efficient CH 4 photooxidation. The direct S‐scheme charge transfer mechanism at the MIL‐125‐NH 2 (Ti)/WO 3 interface enhances spatial separation of photogenerated electron‐hole pairs, thereby optimizing redox efficiency. The WO 3 nanosheets, with their strong oxidative capacity, promote in situ H 2 O 2 generation from water, whereas the Ti 3+ /Ti 4+ redox centers in MIL‐125‐NH 2 (Ti) catalyze H 2 O 2 decomposition into hydroxyl radicals (·OH). These ·OH species efficiently activate the C–H bonds of adsorbed CH 4 , yielding methyl radicals (·CH 3 ). The concurrent generation and coupling of ·OH and ·CH 3 radicals drive selective formation of C 1 oxygenates. Notably, the optimized MW‐3 catalyst exhibits exceptional performance, achieving a total C 1 oxygenate yield of 502.17 μmol·g cat −1 under ambient conditions, surpassing most reported photocatalysts for CH 4 conversion.