Pyridyl‐Imine‐Functionalized Donor–Acceptor Covalent Organic Frameworks for Optimal Photosynthesis of Hydrogen Peroxide

The synthesis of pyridyl-imine-functionalized donor–acceptor covalent organic frameworks (COFs) is reported to optimize photocatalytic H₂O₂ production. By incorporating benzothiadiazole units with different fluorine substitutions, the electronic environment of active sites is tailored, enhancing selective two-electron oxygen reduction. PyIm-BT_F achieves the highest H₂O₂ production rate, highlighting a novel strategy for sustainable H₂O₂ synthesis through rational COF design.

Abstract

The artificial photosynthesis of hydrogen peroxide (H₂O₂) using semiconductor photocatalysts is gaining attention as an eco-friendly and energy-efficient method. Covalent organic frameworks (COFs) show great promise in enhancing photocatalytic H₂O₂ production due to their tunable structures and functional diversity. However, the efficiency of H₂O₂ generation is close to the photoelectric properties of COFs and the microenvironment of their active sites. Herein, the synthesis of pyridyl-imine-functionalized COFs (PyIm-COFs) featuring donor–acceptor (D–A) moieties to improve H₂O₂ production efficiency is reported. By employing benzothiadiazole (BT) units with varied fluorine substitutions, the electronic environment of the active sites, optimizing the selective two-electron (2e⁻) oxygen reduction reaction (ORR), is tuned. Among the synthesized COFs, PyIm-BT_F exhibits the highest photocatalytic activity, achieving a H₂O₂ production rate of 5342 µmol g⁻¹ h⁻¹. The importance of D–A moieties in the rational design of COF-based photocatalysts, providing a novel strategy for sustainable H₂O₂ production through optimized active site environments, is underscored.