Regulating the 2e – ORR Pathway in Tetrazine-Based Covalent Organic Frameworks for Efficient Hydrogen Peroxide Photosynthesis

Covalent organic frameworks (COFs) as emerging oxygen reduction reaction (ORR) photocatalysts have shown great potential for artificial hydrogen peroxide (H2O2) production but often suffered from low generation efficiency following the •O2–-orientated two-step 2e– ORR pathway. In this work, we constructed three isomeric COFs (COF-TpDBT, m-COF-TpDBP, and o-COF-TpDBP) based on tetrazine-cored diamines functionalized with benzene, meta-pyridine, and ortho-pyridine. o-COF-TpDBP with adjacent nitrogen atoms between ortho-pyridine and tetrazine linkage can suppress the two-step 2e– ORR pathway and facilitate a more efficient one-step 2e– ORR pathway, which exhibited remarkable H2O2 photoproduction rates of 6699 μmol h–1 g–1 in pure water and 14017 μmol h–1 g–1 in the presence of benzyl alcohol. The result demonstrated that optimizing the microenvironment around active sites in COFs is an effective strategy to regulate the 2e– ORR pathway for efficient H2O2 photosynthesis.