Recent trends in phenol synthesis by photocatalytic oxidation of benzene.

Phenol is an important intermediate for manufacturing chemical products in industry. In recent decades, phenol synthesis by one-pot oxidation of benzene has aroused tremendous interest in phenol synthesis due to the enormous energy consumption of the three-step cumene method in the industry. Photocatalysis is promising for the selective conversion of benzene to phenol because it can proceed under mild reaction conditions. However, overoxidation of phenol by photocatalysts with high oxidation ability decreases the yield and selectivity, which is the major limiting factor. Thus, increasing the phenol formation efficiency plays a crucial role in photocatalytic systems for benzene oxidation. In this context, selective photocatalytic benzene oxidation over several types of photocatalytic systems has been developed rapidly in the past few years. In this perspective, current homogeneous and heterogeneous photocatalytic systems for this reaction have been reviewed systematically first. Then, an overview of some strategies from the last decade for increasing phenol selectivity has been provided. In the end, a summary and outlook on the challenges and future directions in the research field are included in this perspective, which would be of great interest for further improving the selectivity of the photocatalytic benzene oxidation reaction.