One-dimensional covalent organic frameworks with spatially separated electron–hole distributions for dual-channel charge transfer to enhance photocatalytic H2O2 production
Abstract
Covalent organic frameworks (COFs) are promising photocatalysts for hydrogen peroxide (H2O2) synthesis, yet rapid charge recombination and limited active site exposure remain critical bottlenecks. One-dimensional (1D) COFs, offering superior active site accessibility and weaker interchain interactions than 2D/3D counterparts, represent a compelling structural platform to address these challenges. Herein, we report four 1D COFs incorporating electron donor–acceptor motifs: thienothiophene-based TT- and TF-COF, constructed from a strongly π-conjugated thienothiophene donor, and tetraphenylethylene-based (TPE-based) ET- and EF-COF, built from a propeller-shaped tetraphenylethylene donor. The stronger donor–acceptor character of thienothiophene-based frameworks endows TT- and TF-COF with pronounced intramolecular charge polarization and spatially separated electron–hole distributions, whereas ET- and EF-COF display significant orbital overlap. Photoelectrochemical measurements reveal markedly faster interfacial electron transfer and more efficient charge separation for the thienothiophene-based frameworks than for their TPE-based counterparts, translating into H2O2 production rates of 7959, 7517, 5852, and 5523 µmol g−1 h−1 under visible light without sacrificial agents. The spatial charge separation in TT- and TF-COF suppresses recombination and activates a dual-channel charge transfer mechanism, transcending their 1D structural confinement to achieve multi-dimensional charge delocalization via both intra- and intermolecular pathways. Moreover, TT-COF achieves the highest performance by additionally minimizing the uphill free energy for *OOH intermediate formation (0.87 eV), while also possessing the lightest carriers of the series (reduced effective mass 0.84 m0). This work establishes structure–activity relationships linking monomer selection, donor–acceptor strength, and dual-channel charge transfer to photocatalytic efficiency, offering design principles for next-generation 1D COF-based solar-driven synthesis.