Modulating the Chromophores of Metal‐Covalent Organic Frameworks for Boosting Low‐Concentration CO2 Photoreduction

The development of efficient photocatalysts to convert low‐concentration CO2 into the value‐added chemicals and fuels is particularly interesting yet remains highly challenging. Herein, we designed and synthesized three metal‐covalent organic frameworks (MCOFs) through the Schiff‐base condensation reactions between trinuclear copper complex and different BDP‐based chromophores (BDP = 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene) for visible‐light‐driven reduction of low‐concentration CO2 (15%) to HCOO‐. As a result, MCOF‐ANT containing anthracene (ANT) group achieves the highest HCOO‐ production rate of 1658 μmol g‐1 h‐1 (HCOO‐ selectivity, ~100%) in the absence of any additional noble‐metal photosensitizers under a laboratory light source, which is 7.2 and 2.1 times higher than those of MCOF‐Ph and MCOF‐Nap with phenyl (Ph) and naphthalene (Nap) groups, respectively. Furthermore, MCOF‐ANT also exhibits an excellent photocatalytic activity for the reduction of low‐concentration CO2 (15%) to HCOO‐ under natural sunlight, with a HCOO‐ production rate of 1239 μmol g‐1 h‐1 (HCOO‐ selectivity, ~100%). Experiments and theoretical calculations reveal that the presence of ANT in MCOF‐ANT is favorable to the visible‐light harvesting and charge separation, as well as the formation of *OCO intermediate, which clearly accounts for its superior catalytic activity.