Anthrathiophene-Based Covalent Organic Frameworks with Powerful π-Conjugation toward High-Efficiency CO ₂ Photoconversion

The photocatalytic performance of covalent organic frameworks (COFs) is fundamentally constrained by high exciton binding energies (<i>E</i>_b), which impede efficient exciton dissociation and kinetically retard free-charge carrier generation. In this study, we report the first successful integration of an anthrathiophene unit into a COF backbone, constructing a COF (TA-COF) with an extended π-conjugated system. Concurrently, we developed two distinct COF variants, TF-COF (pyrene-core) and TP-COF (benzene-core), with systematically modulated π-conjugation intensities to enable comparative analysis. The research results indicate that TA-COF, featuring an anthrathiophene-based core, achieved the expanded light response, lower <i>E</i>_b, and accelerated charge transfer impetus and reduced energy barrier of the rate-determining step, finally enabling efficient exciton dissociation, charge separation, and the improvement of photocatalytic activity. TA-COF exhibited exceptional photocatalytic CO₂-to-CO reduction activity (301.5 μmol·g^-1·h^-1) with >90% selectivity under visible light. This work establishes conjugation engineering as a critical lever for optimizing exciton dynamics in COF-based photocatalysis.