Linkage Conversion in Pyrene-based Covalent Organic Frameworks for Promoted Photocatalytic Hydrogen Peroxide Generation in a Biphasic System

The photocatalytic synthesis of hydrogen peroxide (H₂O₂) from water and oxygen using metal-free catalysts represents a promising approach to H₂O₂ production, offering advantages in terms of reduced environmental impact, energy efficiency, and enhanced safety. Covalent organic frameworks (COFs) with imine linkages have emerged as a promising class of materials for this purpose, given their structural and functional diversity. However, they often suffer from poor durability, inefficient photogenerated charge separation efficiency, and rapid recombination of photogenerated electron-hole pairs. To address these limitations, a linkage conversion strategy in COFs can be employed to improve both stability and photoactivity. Herein, we demonstrate the conversion of imine bonds into thiazole rings, thereby facilitating charge transfer and enhancing the photocatalytic stability of COFs. This structural modification enables the thiazole-linked COF to maintain stable photocatalysis over a 24-h period, achieving an H₂O₂ production rate of 57.1 µmol/h (per 10 mg). This rate is twice that of the pristine imine-linked COF and surpasses those of most metal-free photocatalysts. This investigation provides novel insights into the development of advanced COF-based photocatalysts for photocatalytic energy conversions. (Figure presented.)