Three‐Component COFs with D−π−A Units and Side‐Chain‐Enhanced Mass Transfer Enable Efficient Sacrificial‐Agent‐Free H 2 O 2 Photosynthesis

Abstract Photocatalytic oxygen reduction reactions (ORR) and water oxidation reactions (WOR) based on covalent organic frameworks (COFs) represent the most promising green approach for producing H 2 O 2 . However, the enhancement of COFs' photocatalytic efficiency is hindered by the challenge of optimally organizing both donor−acceptor (D−A) units and functional ligands. Herein, three−component COFs with D−π−A units and side chains are designed for achieving higher charge separation efficiency and mass transfer enhancement during photocatalysis. Precisely assembled donor (triphenylamine (TN)) and acceptor (triazine (TA)) in COFs form D−π−A units, in which WOR on TN units can carry out cooperatively with ORR on TA units. The thioether chains within COFs render the formation of gas/liquid/solid three−phase interfaces, which accelerate the oxygen diffusion for ORR. Thus, three−component COFs (TBT−COF) with thioether chains (R 2 S) can reach 7427.25 µmol g −1 h −1 for photocatalytic hydrogen peroxide generation without any sacrificing reagents. The synergy of D−π−A units and mass transfer enhanced by side chains plays very important role in achieving efficient photocatalysis via cooperative ORR/WOR pathways. These results open new possibilities for the fabrication of high−performance COFs‐based photocatalyst.