Enhanced reactive-oxygen-species generation and photocatalytic efficiency with internal imide structures of different ratio in metal-free perylene-g-C3N4 semiconductors

Abstract A metal-free and straightforward protocol for the photocatalytic synthesis of phenols from arylboronic acids has been demonstrated using perylene-tri-s-triazine (perylene-g-C3N4) polymeric semiconductors. Tri-s-triazine and perylene are connected through imide bonds to give catalysts P−M of high imide-bond ratio and P+M of low imide-bond ratio. The aerobic hydroxylation of arylboronic acids can be operated at room temperature and atmospheric environment under white-light LED irradiation. This research work has revealed that internal imide functional groups within the catalyst’s molecular structures can facilitate the ROS (O2 −, OH and 1O2) generation and O2 − is the decisive specie in the hydroxylation due to the faster reaction rate compared with OH and 1O2, with yield as high as 97%. This environment-friendly method and the molecule design principle will provide a valuable strategy for developing metal-free polymeric semiconductors with specific molecular structures and deep insights into the ROS− involved catalysis in photo-generated chemical transformations.