Coulomb Electric Fields Enhanced Charge Separation in Covalent Organic Framework Heterojunctions for Efficient Photocatalytic Hydrogen Production and Biomass Valorization

Abstract Covalent organic frameworks (COFs) have recently emerged as promising candidates for solar fuel production due to their broad spectral absorption and readily tunable optoelectronic properties. However, their photocatalytic performance is often limited by inefficient charge separation and rapid charge recombination. Herein, novel S‐scheme COF heterojunctions is reported by integrating a negatively charged COF host with a positively charged linear conjugated polymer. The electrostatic attraction between them spontaneously generates a robust Coulombic electric field at the heterojunction interface, which shows an identical electric field direction with the intrinsic built‐in electric field of S‐scheme configuration.The control experiments and spectroscopic characterizations reveal that this dual‐field approach significantly enhances directional charge separation and transfer at the interface, effectively suppressing charge recombination. The optimized sample exhibits a highly enhanced photocatalytic hydrogen production rate of 339.4 µmol g −1 h −1 while coupling with a stoichiometric conversion of 5‐hydroxymethyl furfural to 2,5‐diformylfuran.