Donor–Acceptor Fully Sp<sup>2</sup>‐Carbon Conjugated Covalent Organic Frameworks for Photocatalytic H<sub>2</sub>O<sub>2</sub> Production
Xuefeng Wang, Han Li, Shengxiang Zhou, Jing Ning, Hongtao Wei, Xuehui Li, Shitao Wang, Long Hao, Dapeng Cao
Abstract
Abstract Covalent organic frameworks (COFs) are promising for photocatalytic H₂O₂ generation. However, imine‐linked COFs often suffer from poor charge separation and low photocatalytic performance. Therefore, constructing sp 2 carbon‐linked COFs with extended π‐conjugation is very significant in boosting the photocatalytic properties, but their synthesis is challenging due to the low reversibility of C═C bond. Here, two vinylene‐linked COFs: BBT‐ACN COF‐1 and BBT‐ACN COF‐2 are designed. To investigate the effects of different structures on exciton binding energy ( E b ), the designed BBT‐ACN COF‐1 possesses a Donor–Acceptor (D–A) structure with the electron‐deficient benzobisthiazole (BBT) as acceptor and benzotrithiophene as donor, while the latter holds a π‐A structure with pyrene as π‐unit and BBT as acceptor. Both BBT‐ACN COFs show photocatalytic H₂O₂ production activity in a two‐step 2e − oxygen reduction reaction (ORR). As anticipated, the D–A structured BBT‐ACN COF‐1 exhibits a lower E b value, and its photocatalytic H 2 O 2 production rate in pure water and air reaches up to 2.50 mmol g⁻¹ h⁻¹, ≈3 times higher than that of the π‐A structured BBT‐ACN COF‐2 (0.91 mmol g⁻¹ h⁻¹). This study reveals that constructing fully sp 2 ‐carbon‐linked COFs is very beneficial for photocatalytic H 2 O 2 production, which provides an effective approach for designing high‐performance organic photocatalysts.