Recent advances in molecular oxygen activation via photocatalysis and its application in oxidation reactions

[Display omitted] •Molecular oxygen activation via energy and charge transfer processes is summarized.•Molecular oxygen activation pathway analysis and reactive oxygen detection methods are introduced.•Application of activated molecular oxygen in oxidation reactions is reviewed. Molecular oxygen is the greenest potential oxidant, but its spin-forbidden nature limits its activation and application. The use of photocatalysis technology to activate molecular oxygen into reactive oxygen species (ROS) is a feasible strategy for initiating molecular oxygen activation performance from the activation methods of energy transfer process and charge transfer process, such as improving the efficiency of inter-system crossing, reducing non-radiative decay, and enhancing molecular oxygen adsorption and charge separation efficiency. New perspectives on the analysis of molecular oxygen activation pathways and the detection methods of ROS are introduced. In addition, the application of activated molecular oxygen in some oxidative reactions including degradation of organic pollutants, organic synthesis and photodynamic therapy of tumors are summarized. Finally, conclusions and challenges are briefly presented.