Selective heterogeneous photocatalytic activation for toluene oxidation: recent advances, challenges and perspective

The conversion of toluene into high-value products without generating undesired CO2 remains a critical challenge. Selective oxidation of toluene under visible light irradiation has emerged as a promising solution. This review offers a comprehensive interpretation of photocatalytic transformations in heterogeneous toluene oxidation. We start by outlining the basic mechanism of C–H bond activation of toluene and provide an overview of reactive oxygen species (ROS) within photocatalytic systems. Subsequently, we provide a summary of strategies that have been developed to enhance the conversion and selectivity of the heterogeneous photocatalytic system. Following this, advanced characterization techniques and density functional theory (DFT) calculations are discussed for understanding the structure-performance relationship of photocatalysts and the mechanisms underlying photocatalytic processes. Finally, we put forward a detailed discussion of current challenges and potential directions for future research, with the aim of offering valuable insights for this emerging field. We believe that this review will not only spark greater creativity in optimizing photocatalysts but also offer valuable insights for designing other C–H bond activation systems.