Gradient-Polarized COFs for Paired H₂O₂/Imine Photosynthesis

Photocatalytic hydrogen peroxide (H₂O₂) synthesis coupled with organic oxidation offers an efficient approach for solar-to-chemical conversion but is limited by inefficient charge separation and mismatched redox kinetics. We present a gradient-polarized covalent organic framework (COF) platform, achieved by strengthening benzothiadiazole-based acceptor units along a conjugated donor backbone. This gradient polarization creates a directional charge-migration field, enhancing exciton dissociation and synchronizing electron–proton utilization in paired redox reactions. Optimized BTD-BTT-COF exhibits a high H₂O₂ production rate of 25.67 mmolg^‒1 h^‒1 (AQY = 18.4%), achieving nearly quantitative benzylamine-to-imine conversion (>99% yield, >99.9% selectivity), and excellent stability. Spectroscopic analysis, isotopic labeling, and DFT calculations show that gradient polarization suppresses charge recombination and promotes electron accumulation at thiadiazole-rich regions, enhancing oxygen activation, stabilizing superoxide and *OOH intermediates, and lowering the kinetic barrier of the ORR pathway. Coupled benzylamine (BnAm) oxidation further extracts holes and supplies protons for proton-coupled electron transfer, amplifying catalytic turnover. This work establishes gradient polarization as a general design principle for COF photocatalysts, enabling efficient charge and reaction kinetics regulation in paired photosynthetic systems.