High-density integration of MOF/COF via ligand intercalation boosts photocatalytic CO2 reduction under low-concentration conditions

Designing the photocatalyst that possesses both efficient diluted carbon dioxide (CO 2 ) enrichment and photocatalytic conversion capabilities is a key challenge for the direct utilization of low-concentration CO 2 (15%) from flue gas. Herein, we proposed an interlayer ligand insertion strategy to construct a high-density integrated adsorption-catalysis system between NH 2 -UiO-66(Zr) (U66N) and functionalized TPB-DMTP-COF with benzoic acid groups (COF-T) for highly efficient photocatalytic diluted CO 2 reduction. In the photocatalytic CO 2 reduction reaction, the diluted CO 2 was first adsorbed and enriched to the microporous structure constructed between COF-T and U66N. Simultaneously, the two-dimensional COF-T acts as the primary light-harvesting component, preferentially capturing photogenerated electrons and holes under visible light and directing their transport to the catalytic interface of the three-dimensional U66N through steric-hindrance-induced distorted coordination linkages. Then the CO 2 molecules progressively activated by using the delivered electrons and H + , ultimately converting into CO. This ordered high-density integration architecture of COF and MOF concurrently optimizes light absorption and charge transfer pathways, enables precise regulation of the catalytic centers, and thereby substantially lowers the energy barrier for the formation of the *COOH intermediate in the photocatalytic CO 2 reduction, resulting in enhanced overall catalytic performance. Consequently, COF-T/U66N achieves a remarkable CO production rate of 65.0 µmol·g -1 ·h -1 under diluted CO 2 (15%), with near-unity (∼100%) selectivity and without adding any photosensitizer and sacrificial agent, surpassing state-of-the-art inorganic or porous photocatalysts by 5–40 times. This work not only provides a feasible strategy for the efficient photocatalytic reduction of low-concentration CO 2 but also offers a universal method for the design of MOF/COF composite materials.