Photocatalytic aerobic oxidation by using oxygen molecules (O₂) as green and low-cost oxidants is of great attraction, where the introduction of irradiation has been proved as an efficient strategy to lower reaction temperature as well as promote catalytic performance. Moreover, the oxygen vacancies (OVs) of catalyst are highly active sites to adsorb and activate O₂ during photocatalytic aerobic oxidation. However, OVs are easily blocked by oxygen atoms from active oxygen species during the catalytic process, leading to the deactivation of catalysis. Herein, a promising catalyst toward photocatalytic aerobic oxidation was successfully developed by recovering the OVs through doping Au atoms into Ti₃C₂T_x MXene (Au/Ti₃C₂T_x). Impressively, Au/Ti₃C₂T_x exhibited remarkable activity under full-spectrum irradiation towards photooxidation of methyl phenyl sulfide (MPS) and methylene blue (MB), attaining a conversion of >90% at room temperature. Moreover, Au/Ti ₃C₂T_x also manifested remarkable stability by maintaining >95% initial activity after 10 successive reaction rounds. Further mechanistic studies indicated that the OVs of Au/Ti ₃C₂T_x served as the active centers to efficiently adsorb and activate O₂. More importantly, the doped Au atoms of Au/Ti₃C₂T_x were conducive to the recovery of OVs during photocatalytic process from the results of theoretical and experimental aspects. The recovered OVs of Au/Ti₃C₂T_x continuously and efficiently activated O₂, directly contributing to the remarkable catalytic activity and stability.

Aerobic oxidation by using molecular oxygen (O₂) as the oxidant is highly attractive, in which activating O₂ to reactive oxygen species (ROS) is a prerequisite. Although some progress has been achieved in regulating ROS by heterogeneous catalysts, the strategies to efficiently control ROS in aerobic oxidation are still urgently desired. Herein, grain boundaries (GBs) in metal oxides are discovered to be able to facilely regulate ROS. Impressively, MoO₃ nanocrystals with high density of GBs (MoO₃-600) deliver a mass activity of 83 mmol g^-1 h^-1 in aerobic oxidation of benzyl alcohol, 7 and 8 times as high as that of MoO₃ nanoparticles without GBs and Pt/C, respectively. In addition, the selectivity of benzoic acid is 100% during whole reaction process over MoO₃-600. Mechanistic studies reveal that the oxygen atoms at GBs in MoO₃-600 are highly active to form ∙OH radicals with the generation of oxygen vacancies, while the oxygen vacancies are replenished by O₂. The reaction path directly contributes to the excellent catalytic performance.