Efficient Photosynthesis of Hydrogen Peroxide by Cyano‐Containing Covalent Organic Frameworks from Water, Air and Sunlight

Abstract The insufficient exciton ( e − ‐ h + pair) separation/transfer and sluggish two‐electron water oxidation are two main factors limiting the H 2 O 2 photosynthetic efficiency of covalent organic frameworks (COFs) photocatalysts. Herein, we present an alternative strategy to simultaneously facilitate exciton separation/transfer and reduce the energy barrier of two‐electron water oxidation in COFs via a dicyano functionalization. The in situ characterization and theoretical calculations reveal that the dicyano functionalization improves the amount of charge transfer channels between donor and acceptor units from two in COF‐0CN without cyano functionalization to three in COF‐1CN with mono‐cyano functionalization and four in COF‐2CN with dicyano functionalization, leading to the highest separation/transfer efficiency in COF‐2CN. More importantly, the dicyano group activates the neighbouring C atom to produce the key *OH intermediate for effectively reducing the energy barrier of rate‐determining two‐electron water oxidation in H 2 O 2 photosynthesis. The simultaneously enhanced exciton separation/transfer and two‐electron water oxidation in COF‐2CN result in high H 2 O 2 yield (1601 μmol g −1 h −1 ) from water and oxygen without using sacrificial reagent under visible‐light irradiation. COF‐2CN can effectively yield H 2 O 2 in water with wide pH range, in different real water samples, in scaled‐up reactor under natural sunlight irradiation, and in continuous‐flow reactor for consecutively producing H 2 O 2 solution for water decontamination.