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Photocatalytic H 2 O 2 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 H 2 O 2 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 H 2 O 2 production via dominated two-electron O 2 reduction processes, including O 2 -O 2 •‒ -H 2 O 2 and O 2 -O 2 •‒ -O 2 1 -H 2 O 2 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 H 2 O 2 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 O 2 •‒ and O 2 1 in different catalytic process. This study gives a new insight into designing photocatalysis at atomic level., (© 2024 Wiley‐VCH GmbH.)

Photocatalytic oxygen reduction reactions and water oxidation reactions are extremely promising green approaches for massive H 2 O 2 production. Nonetheless, constructing effective photocatalysts for H 2 O 2 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 H 2 O 2 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 H 2 O 2 photoproduction performance (6085 and 5448 μmol g -1  h -1 in O 2 and air) than TBC-COF with hcb topology through the O 2 -O 2 ⋅ - -H 2 O 2 , O 2 -O 2 ⋅ - -O 2 1 -H 2 O 2 , and H 2 O-H 2 O 2 three paths. Further experimental and theoretical investigations confirmed that during the H 2 O 2 photosynthetic process, the charge carrier separation efficiency, O 2 ⋅ - generation and conversion, and the energy barrier of the rate determination steps in the three channels, related to the formation of *OOH, *O 2 1 , and *OH, can be well tuned by the topology of COFs. The current study enlightens the fabrication of high-performance photocatalysts for H 2 O 2 production by topological structure modulation., (© 2024 Wiley-VCH GmbH.)

H 2 O 2 is a significant chemical widely utilized in the environmental and industrial fields, with growing global demand. Without sacrificial agents, simultaneous photocatalyzed H 2 O 2 synthesis through the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels from seawater is green and sustainable but still challenging. Herein, two novel thiophene-containing covalent organic frameworks (TD-COF and TT-COF) were first constructed and served as catalysts for H 2 O 2 synthesis via indirect 2e - ORR and direct 2e - WOR channels. The photocatalytic H 2 O 2 production performance can be regulated by adjusting the N-heterocycle modules (pyridine and triazine) in COFs. Notably, with no sacrificial agents, just using air and water as raw materials, TD-COF exhibited high H 2 O 2 production yields of 4060 μmol h -1  g -1 and 3364 μmol h -1  g -1 in deionized water and natural seawater, respectively. Further computational mechanism studies revealed that the thiophene was the primary photoreduction unit for ORR, while the benzene ring (linked to the thiophene by the imine bond) was the central photooxidation unit for WOR. The current work exploits thiophene-containing COFs for overall photocatalytic H 2 O 2 synthesis via ORR and WOR dual channels and provides fresh insight into creating innovative catalysts for photocatalyzing H 2 O 2 synthesis., (© 2023 Wiley-VCH GmbH.)