Iodine doping covalent organic frameworks to reduce electron-hole recombination for promoting photocatalytic performance

Reducing photogenerated charge recombination is critical for improving photocatalytic performance. Covalent organic frameworks (COFs) are promising semiconductor photocatalysts, but their photocatalytic performance is still subjected to inefficient charge transfer and high electron-hole recombination, which is induced by the inherent strong Coulomb binding. Therefore, exploring strategies to suppress electron-hole recombination is crucial for improving photocatalytic efficiency. Herein, three COFs with different charge transfer behaviors were constructed by doping anionic I− and I3−/I5− onto the imine bonds of aniline-based COFs (BCTA-DHPA). Notably, the I− doped COF (COF3) showed a high photocatalytic uranium extraction efficiency of 8.33 mg/(g day) in natural seawater. Doping anionic I− and I3−/I5− triggers the generation of charge transfer excited states and polarons, which significantly inhibit the recombination of photogenerated electrons. This study offers an effective method to reduce electron-hole recombination and enhance photocatalytic performance of semiconductor photocatalysts. It is expected to deepen understanding of photocatalytic processes and mechanisms.