Regulating Benzene Ring Number as Connector in Covalent Organic Framework for Boosting Photosynthesis of H2O2 from Seawater

Photosynthesis of H₂O₂ from seawater represents a promising pathway to acquire H₂O₂, but it is still restricted by the lack of a highly active photocatalyst. In this work, we propose a convenient strategy of regulating the number of benzene rings to boost the catalytic activity of materials. This is demonstrated by ECUT-COF-31 with adding two benzene rings as the connector, which can result in 1.7-fold enhancement in the H₂O₂ production rate relative to ECUT-COF-30 with just one benzene ring as the connector. The reason for enhancement is mainly due to the release of *OOH from the surface of catalyst and the final formation of H₂O₂ being easier in ECUT-COF-31 than in ECUT-COF-30. Moreover, ECUT-COF-31 provides a stable photogeneration of H₂O₂ for 70 h, and a theoretically remarkable H₂O₂ production of 58.7 mmol per day from seawater using one gram of photocatalyst, while the cost of the used raw material is as low as 0.24 $/g.