Nitrogen‐Site Engineering in Covalent Organic Frameworks for H ₂ O ₂ Photogeneration via Dual Channels of Indirect Two‐Electron O ₂ Reduction

Photocatalytic H₂O₂ production is a green and sustainable route, but far from meeting the increasing demands of industrialization due to the rapid recombination of the photogenerated charge carriers and the sluggish reaction kinetics. Effective strategies for precisely regulating the photogenerated carrier behavior and catalytic activity to construct high-performance photocatalysts are urgently needed. Herein, a nitrogen-site engineering strategy, implying elaborately tuning the species and densities of nitrogen atoms, is applied for H₂O₂ photogeneration performance regulation. Different nitrogen heterocycles, such as pyridine, pyrimidine, and triazine units, are polymerized with trithiophene units, and five covalent organic frameworks (COFs) with distinct nitrogen species and densities on the skeletons are obtained. Fascinatingly, they photocatalyzed H₂O₂ production via dominated two-electron O₂ reduction processes, including O₂-O₂ ^•‒-H₂O₂ and O₂-O₂ ^•‒-O₂ ¹-H₂O₂ dual pathways. Just in the air and pure water, the multicomponent TTA-TF-COF with the maximum nitrogen densities triazine nitrogen densities exhibited the highest H₂O₂ production rate of 3343 µmol g^-1 h^-1, higher than most of other reported COFs. The theoretical calculation revealed the higher activity is due to the easy formation of O₂ ^•‒ and O₂ ¹ in different catalytic process. This study gives a new insight into designing photocatalysis at atomic level.