Abstracting photogenerated holes from covalent triazine frameworks through carbon dots for overall hydrogen peroxide photosynthesis

Abstract

Owing to the rapid recombination of photogenerated electron-hole pairs with strong Coulomb interactions, the photocatalytic activity of metal-free conjugated polymers is often unsatisfactory. This article reports a simple method for incorporating carbon dots (CDs) into highly crystalline covalent triazine frameworks (CTFs) by directly heating a pretreated mixture of 1,4-dicyanobenzene, CDs, and alkali metal salts in air. The resultant photocatalyst exhibits a H₂O₂ production rate, solar-to-chemical conversion efficiency, and apparent quantum yield of 2464 μmol h^–1 g^–1, 0.9% at full spectrum, and 13% at 500 nm, respectively, surpassing most reported photocatalysts. The results of this study reveal that CDs can serve as hole extractors to efficiently drive exciton dissociation and can offer active sites for water oxidation reactions. This study is also the first to observe that alkali metal ions can interact with the carboxylic acid groups on the surface of CDs during synthesis to enhance the hole-extraction ability of CTFs, thereby accelerating photocatalytic H₂O₂ production. This study provides insights into the rational design of highly efficient CDs-based photocatalysts.