Donor–Acceptor Fully Sp2‐Carbon Conjugated Covalent Organic Frameworks for Photocatalytic H2O2 Production

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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 sp2 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 (Eb), 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 Eb value, and its photocatalytic H2O2 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 sp2‐carbon‐linked COFs is very beneficial for photocatalytic H2O2 production, which provides an effective approach for designing high‐performance organic photocatalysts.
Funding Information
  • National Natural Science Foundation of China (51603114)
  • Natural Science Foundation of Shandong Province (ZR2021MB067, ZR2019PB002)

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