Construction of Benzothiadiazolequinoxaline-Based Donor–Acceptor Covalent Organic Framework for the Efficient Photocatalytic Oxidation of Sulfides

Donor-acceptor (D-A)-type covalent organic frameworks show promising potential as photocatalysts for oxidation reactions due to their highly tunable structures and band gaps. Benzothiadiazolequinoxaline (BTQ), a strong electron-withdrawing acceptor, serves as a suitable unit for constructing D-A-type COFs. Herein, two BTQ-based D-A COFs (TAPB-BTQ-COF and PPy-BTQ-COF) with different electron-donating units were designed and synthesized for the photooxidation of sulfides. Experimental measurements and theoretical calculations reveal that TAPB-BTQ-COF exhibits s broader absorption range, smaller charge resistance, and stronger photocurrent response compared to PPy-BTQ-COF. Moreover, TAPB-BTQ-COF exhibits a significantly lower exciton binding energy and an extended photoluminescence emission lifetime compared to PPy-BTQ-COF. These characteristics effectively facilitate exciton dissociation and suppress charge recombination, thereby endowing TAPB-BTQ-COF with superior photocatalytic performance. As a result, TAPB-BTQ-COF achieves an exceptional photocatalytic yield of 95% for sulfide oxidation within 6 h while maintaining remarkable stability. Additionally, TAPB-BTQ-COF demonstrates an enhanced intersystem crossing process, enabling enhanced generation of both singlet oxygen (¹O₂) and superoxide anion (O₂^•-). This work provides valuable insights for engineering BTQ-based COFs for highly efficient organic transformations.