Integrating Multipolar Structures and Carboxyl Groups in sp²-Carbon Conjugated Covalent Organic Frameworks for...

The direct production of hydrogen peroxide (H₂O₂) through photocatalytic reaction via H₂O and O₂ is considered as an ideal approach. However, the efficiency of H₂O₂ generation is generally limited by insufficient charge and mass transfer. Covalent organic framework (COFs) offer a promising platform as metal-free photocatalyst for H₂O₂ production due to their potential for rational design at the molecular level. Herein, we integrated the multipolar structures and carboxyl groups into COFs to enhance the efficiency of photocatalytic H₂O₂ production in pure water without any sacrificial agents. The introduction of octupolar and quadrupolar structures, along with an increase of molecular planarity, created efficient oxygen reduction reaction (ORR) sites. Meanwhile, carboxyl groups could not only boost O₂ and H₂O₂ movement via enhancement of pore hydrophilicity, but also promote proton conduction, enabling the conversion to H₂O₂ from ⋅O₂ ^-, which is the crucial intermediate product in H₂O₂ photocatalysis. Overall, we demonstrate that TACOF-1-COOH, consisting of optimal octupolar and quadrupolar structures, along with enrichment sites (carboxyl groups), exhibited a H₂O₂ yield rate of 3542 μmol h^{- 1} g^-1 and a solar-to-chemical (SCC) efficiency of 0.55 %. This work provides valuable insights for designing metal-free photocatalysts for efficient H₂O₂ production.