Protonation Strategy‐Enhanced Metal‐Free Selective Photocatalytic Oxidation of Thioethers of Tetracyanoanthraquinone‐Based Covalent Organic Polymers

Abstract The cyano group with a strong electron‐withdrawing ability is widely used to regulate the electronic structure of optoelectronic molecules in OLED devices. Covalent organic polymers (COPs), as a category of promising photocatalysts, are favored for their excellent structural controllability. In this study, we synthesized a tetracyanoanthraquinone‐functionalized COP (TCAQ‐COP). Notably, a simple protonation treatment of TCAQ‐COP (designated as TCAQ‐COPH) can tremendously improve its visible‐light absorption capacity and optimize its energy level structure. Subsequently, taking the photocatalytic oxidation of thioethers to sulfones as a model reaction, we demonstrated that protonation not only improved the separation and transfer efficiency of photogenerated charges but also enhanced the selectivity and conversion efficiency of the photocatalytic oxidation process. Mechanistic investigations revealed that the incorporation of cyano groups and the protonation of carbonyl oxygens are critical factors driving the superior photocatalytic performance of TCAQ‐COPH.