Regulating the generation of reactive oxygen species for photocatalytic oxidation by metalloporphyrinic covalent organic frameworks

Regulating the generation of reactive oxygen species (ROS) impacts the selectivity and activity of photocatalytic oxidation, but the frequently concurrent formation of different types of ROS makes this process rather challenging. This study demonstrates the regulated production of two important ROS, O-1(2) and O-2(center dot-), using a covalent-organic framework (COF) array with three members, which are made up of metalloporphyrin cores with embedded center metal ions from d-block transition metals sequentially arranged in the periodic table. Due to the evolution of the electronic structures in this COF array, the production of O-1(2) and O-2(center dot-) is controlled, which successively leads to distinct performance in photocatalytic aerobic oxidations. The electronic property study and density-functional theory (DFT) calculations revealed that the distinct excitonic behavior of three COFs in regulated O-1(2) and O-2(center dot-) generation is rooted in their different band energy levels and O-2 adsorption ability. Our work presents an effective approach to the controlled production of ROS for improved photocatalytic performance.