Direct Photocatalytic Conversion of Methane to Acetone Through a Synergistic Ta Single-Atom/Ga Lewis Acid Catalyst

Direct photocatalytic conversion of methane to ≥ C3 oxygenates under ambient conditions remains highly challenging and largely unexplored due to the current carbon-terminated adsorption configurations and insufficient concentration of intermediates. Herein, we demonstrated efficient γ-Ga₂O₃ quantum dot catalysts with high-density Ta single atoms anchored at Ga_IV vacancies (Ta₁-Ga₂O₃ QDs), featuring a synergistic Ta single-atom/Ga Lewis acid architecture. The unsaturated d⁰-TaO₄ site stabilizes key acetyl intermediates in a distinctive oxygen-terminated η¹(O)-CH₃CO configuration, minimizing steric hindrance while enhancing carbonyl carbon electrophilicity, greatly facilitating the second C-C coupling step. Concurrently, Ga sites enrich -CH₃ intermediates for sequential C-C coupling conversion. The synergistic architecture achieved single-step photocatalytic conversion of CH₄ and H₂O to acetone with a yield of 86.7 µmol g^-1 h^-1, with the carbon-based selectivity of 56.2% or the liquid phase selectivity of 81.2%, and a 20.7% apparent quantum yield (AQY) at 254 nm, which has not been achieved by the current noble metal-based photocatalysts. This work demonstrates the unique capability of unsaturated d⁰ single-atom sites for modulation of intermediate configurations, unlocking a pathway for ≥ C3 oxygenate synthesis from methane.