Regulating pi-Conjugation in sp(2)-Carbon-Linked Covalent Organic Frameworks for Efficient Metal-Free CO2 Photoreduction with H2O

The development of sp(2)-carbon-linked covalent organic frameworks (sp(2)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 sp(2)c-COFs by rationally regulating their intrinsic pi-conjugation. The incorporation of ethynyl groups into conjugated skeletons affords a significant improvement in pi-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 mu mol 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 pi-conjugated COF-based artificial photocatalysts.