Symmetry-Breaking Covalent Organic Frameworks with Topological Defects and N,N-Dimethylamino Functionalization for Photosynthesis of H2O2

Artificial photosynthesis based on covalent organic frameworks (COFs) is a promising next-generation method for producing hydrogen peroxide (H2O2) because of its low cost, ease of operation, and sustainability. However, limited charge separation/transport and a lack of highly active sites hinder further efficiency improvements. In this study, we used a symmetry-breaking strategy to construct a deformed hcb topology with order defects, which can be filled with functional groups. Without any sacrificial reagents, the defective and N,N-dimethylamino-functionalized COF (TpDdat) showed significantly enhanced photocatalytic performance with a superior H2O2 production rate of 11296 μmol g-1 h-1, far surpassing its counterpart with inactive functional groups or higher symmetry. Its apparent quantum yield and solar-to-chemical energy conversion efficiency reached 13.0% at 420 nm and 1.06%, respectively. A continuous-flow photocatalytic microreactor system based on TpDdat demonstrated a stable yield of 10.7 μmol h-1, generating a 1.36 mM H2O2 aqueous solution over 24 hours. Systematic experiments and theoretical calculations indicated that topological defects and N,N-dimethylamino groups facilitated the separation and migration of photogenerated electron-hole pairs, while providing active sites for the oxygen reduction reaction. This work offers a strategy for designing COFs co-functionalized with topological defects and functional groups to enable efficient photosynthesis of H2O2.