Interfacial Engineering of β‐Ketoenamine‐Based COFs/Urea‐Linked Perylene Diimide for Overall Photosynthesis of H 2 O 2 in Seawater

High‐efficiently non‐sacrificial H 2 O 2 production is challenging due to the sluggish kinetics of ORR and WOR and severe electron‐hole recombination. Via interfacial engineering, a series of non‐metal photocatalysts are rationally designed and constructed, covalently bonded TpDT‐COF (TP) and urea‐PDI (UP), to achieve high non‐sacrificially photocatalytic H 2 O 2 production in seawater. Experimental and theoretical analysis has revealed that an interfacial electric field is formed between covalently bonded TP and UP, which provides an internal driving force to enhance the electron‐hole separation. Further mechanistic studies reveal that the H 2 O 2 production follows a simultaneous two‐step 2e − ORR and 4e − OER route. Moreover, the activity toward OER of the active center at the UP is significantly promoted due to a net charge transfer from UP to TP after covalently bonding. As a result, a high non‐sacrificial H 2 O 2 production rate of 3846 µmol gh −1 in seawater is achieved. Furthermore, a 4.7 mM H 2 O 2 is obtained after a 13 h‐continuous photocatalytic reaction, which can be directly used to purify dye and phenol contaminated water. Notably, the strategy of creating interfacial electric field coupled with desired charge transfer provides a universal approach for non‐sacrificial photosynthesis by enhancing the electron‐hole separation and activity of catalytic centers simultaneously.