β-Ketoenamine-Linked Triazine Covalent Organic Frameworks for Efficient Solar-Driven Hydrogen Peroxide Production from Water and Air

Abstract

Developing efficient photocatalytic systems for oxygen activation and the green synthesis of hydrogen peroxide (H₂O₂) is a critical challenge in sustainable energy conversion technologies. Covalent organic frameworks (COFs) exhibit unique advantages in visible-light-driven H₂O₂ production due to their tunable crystalline structures and optoelectronic properties. However, the structure–activity relationships governing their composition, structure, and performance remain elusive. In this study, we synthesized three crystalline COF photocatalysts through molecular topology engineering, systematically revealing the synergistic regulation mechanism of monomers and linkages on the photocatalytic performance. The results show that β-ketoenamine-linked triazine TTPT-COF exhibits exceptional photocatalytic activity, with a H₂O₂ yield of 2650 μmol g^–1 h^–1 in visible light and O₂, and 1230 μmol g^–1 h^–1 in outdoor sunlight and air, surpassing most reported crystalline photocatalysts. Electrochemistry, in situ Fourier transform infrared spectroscopy, and theoretical calculation results demonstrated that the synergistic interplay between the triazine unit and β-ketoenamine linkage significantly enhances charge separation efficiency and prolongs carrier lifetime and also plays a key role in promoting oxygen activation. Furthermore, TTPT-COF achieved a 14.7% yield for the selective aerobic oxidation of benzyl alcohol to benzaldehyde, thereby validating its oxygen activation capability. This work elucidates the molecular-level synergy between monomers and linkages in COFs, providing a theoretical foundation and design principles for developing advanced solar-driven H₂O₂ synthesis systems.