Regulating π‐Conjugation in sp ² ‐Carbon‐Linked Covalent Organic Frameworks for Efficient Metal‐Free CO ₂ Photoreduction with H ₂ O

The development of sp2 -carbon-linked covalent organic frameworks (sp2 c-COFs) as artificial photocatalysts for solar-driven conversion of CO2 into chemical feedstock has captured growing attention, but catalytic performance has been significantly limited by their intrinsic organic linkages. Here, a simple, yet efficient approach is reported to improve the CO2 photoreduction on metal-free sp2 c-COFs by rationally regulating their intrinsic π-conjugation. The incorporation of ethynyl groups into conjugated skeletons affords a significant improvement in π-conjugation and facilitates the photogenerated charge separation and transfer, thereby boosting the CO2 photoreduction in a solid-gas mode with only water vapor and CO2 . The resultant CO production rate reaches as high as 382.0 µmol g-1 h-1 , ranking at the top among all additive-free CO2 photoreduction catalysts. The simple modulation approach not only enables to achieve enhanced CO2 reduction performance but also simultaneously gives a rise to extend the understanding of structure-property relationship and offer new possibilities for the development of new π-conjugated COF-based artificial photocatalysts.