Anion Engineering of Surface Frustrated Lewis Pairs for Light-Assisted CO₂ Hydrogenation to Methanol

Surface frustrated Lewis pairs (SFLPs) have been widely studied as active sites for light-assisted CO₂ hydrogenation, while most efforts have focused on cation engineering to tune the Lewis acidity of metal centers, leaving the Lewis-basic component less directly controlled. Here, we report an anion engineering strategy based on nitridation to prepare nitrogen-doped, non-stoichiometric spinel zinc gallium oxide catalysts for CO₂ hydrogenation to methanol. Nitrogen incorporation modifies the local anion coordination environment, promotes oxygen vacancy formation, and reconstructs the coordination structure around Ga sites, thereby generating defect-associated Ga-O/N Lewis acid-base pairs that favor heterolytic H₂ splitting. Nitridation also narrows the band gap and introduces localized electronic states, leading to improved light absorption. As a result, the optimized catalyst achieves a methanol production rate of 1203.7 µmol h^-1 g^-1 with enhanced methanol selectivity and apparent quantum efficiency (AQE) under illumination. This work demonstrates that anion engineering provides an effective route to regulate oxide SFLPs and promote light-assisted CO₂ hydrogenation to methanol.