Superhydrophilic covalent organic frameworks accelerate photocatalytic production of hydrogen peroxide through proton channels

Abstract

The synthesis of hydrogen peroxide (H₂O₂) involves the simultaneous transfer of electrons and protons. Enhancing the mobility of these particles can significantly improve the efficiency of photocatalytic production of H₂O₂. Herein, proton donor groups were introduced into covalent organic frameworks (COFs) to make them superhydrophilic. These COFs have an electron donor–acceptor (D–A) structure consisting of imine and quinoline linkages. The proton donor groups (hydroxyl and carboxyl groups) in each COF channel form a hydrogen-bonding network with water, forming a hydrophilic zone around the channel. This configuration effectively uses water molecules as proton supply reservoirs and facilitates the transfer of protons to the photocatalysts, thus improving the photocatalytic synthesis of H₂O₂. The superhydrophilic TAPT–DHA showed a significantly higher photocatalytic H₂O₂ generation rate of 1629 µmol g⁻¹ h⁻¹ in pure water under simulated sunlight irradiation compared to its counterpart lacking proton donor groups (446 µmol g⁻¹ h⁻¹). These results highlight the enhanced electron and proton transfer capabilities of COFs. The findings of this study provide valuable insights into the design and development of COFs for efficient photocatalytic production of H₂O₂.