Engineering Metal‐Salen Covalent Organic Polymers for Boosted H ₂ O ₂ Photosynthesis and Coupled Environmental Remediation

Photocatalytic oxygen reduction reaction (ORR) is a promising route for sustainable H 2 O 2 synthesis, enabling on‐demand production and in situ water remediation, yet it is still hampered by poor charge separation and migration, as well as sluggish O 2 adsorption and activation. Herein, salen‐based covalent organic polymers (COPs) possessing tunable metal site numbers and coordination environments are designed for photocatalytic H 2 O 2 synthesis. Among them, ZnZn‐salen‐COP achieves an efficient H 2 O 2 production rate of 8577 µmol g −1 h −1 in 10% benzyl alcohol (BA) without oxygen aeration, generating high‐value compound, benzaldehyde (BAD) with a production rate of 24 mmol g −1 h −1 . The experimental study and theoretical calculation confirm that the dual metallosalen structure promotes visible‐light absorption and charge carrier separation efficiency, boosting O 2 adsorption and lowering the reaction potential barrier, enabling H 2 O 2 production mainly via indirect 2e − ORR. Furthermore, ZnZn‐salen‐COP enables efficient H 2 O 2 production for in situ uranium extraction (98% efficiency) and organic degradation (methyl orange ∼100%, BPA∼98.4% and tetracycline ∼94.1%). This work provides insight into designing highly efficient photocatalysts for water treatment via in situ H 2 O 2 generation by engineering metal sites and coordination environments.