Tuning the exciton binding energy of covalent organic frameworks for efficient photocatalysis

Owing to the large exciton binding energy ( > 100 meV) of most organic materials, the process of exciton dissociation into free electrons and holes is seriously hindered, which plays a key role in the photocatalytic system. In this study, a series of chalcogen (S, Se)-substituted mesoporous covalent organic frame-works (COFs) have been synthesized for enhanced photocatalytic organic transformations. Photoelectro-chemical measurements indicate that the introduction of semi-metallic Se atom and the enlargement of conjugation degree can not only reduce the exciton binding energy accelerating the charge separation, but also reduce the band gap of COFs. As a result, the COF-NUST-36 with the lowest exciton binding energy (39.5 meV) shows the highest photocatalytic performance for selective oxidation of amines (up to 98% Conv. and 97.5% Sel.). This work provides a feasible method for designing COFs with high photocatalytic activity by adjusting exciton binding energy. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.