Regulating the Topology of Covalent Organic Frameworks for Boosting Overall H₂O₂ Photogeneration

Abstract

Photocatalytic oxygen reduction reactions and water oxidation reactions are extremely promising green approaches for massive H₂O₂ production. Nonetheless, constructing effective photocatalysts for H₂O₂ generation is critical and still challenging. Since the network topology has significant impacts on the electronic properties of two dimensional (2D) polymers, herein, for the first time, we regulated the H₂O₂ photosynthetic activity of 2D covalent organic frameworks (COFs) by topology. Through designing the linking sites of the monomers, we synthesized a pair of novel COFs with similar chemical components on the backbones but distinct topologies. Without sacrificial agents, TBD-COF with cpt topology exhibited superior H₂O₂ photoproduction performance (6085 and 5448 μmol g^-1 h^-1 in O₂ and air) than TBC-COF with hcb topology through the O₂-O₂⋅^--H₂O₂, O₂-O₂⋅^--O₂ ¹-H₂O₂, and H₂O-H₂O₂ three paths. Further experimental and theoretical investigations confirmed that during the H₂O₂ photosynthetic process, the charge carrier separation efficiency, O₂⋅^- generation and conversion, and the energy barrier of the rate determination steps in the three channels, related to the formation of *OOH, *O₂ ¹, and *OH, can be well tuned by the topology of COFs. The current study enlightens the fabrication of high-performance photocatalysts for H₂O₂ production by topological structure modulation.