Dimensional Engineering of 1D/2D Covalent Organic Framework Isomers for Enhanced CO₂ Photoreduction.

The rigorous topologic 1D covalent organic frameworks (1D-COFs) require highly anisotropic and aligned connectivity, making their synthesis as isomers with low-dimensional structures challenging, let alone understanding the long-sought consensus regarding the structure-property relationship. Here, a feasible dimensional engineering strategy is demonstrated to construct 1D/2D COF isomers, revealing their dimensional contributions on the photocatalytic CO reduction reaction (CO-RR) performance. By leveraging the cis/trans conformational flexibility of 2,2'-bipyridine-4,4'-dicarboxaldehyde (BPY) under acidity regulation, this study successfully constructs 1D/2D BPY-COF dimensional isomers for the first time. To give prominence to the dimensional topological effect, the post-modification of cobalt (Co) is coordinated with bipyridine in 1D/2D-BPY-COFs. Notably, the unique 1D chain structure and more exposed catalytic sites on the edge of 1D-BPY-COF-Co, significantly facilitate the orientational electron transfer, making the formation energy (ΔG ) for COOH lowering from 0.78 eV in 2D-BPY-COF-Co to 0.25 eV. This structural advantage contributes to an exceptionally high CO yield of 1645 µmol g h with 100% selectivity, which exceeds that of the corresponding 2D counterpart by a factor of 108. This work initiates a new progress for dimensional control in reticular chemistry, providing fundamental insights into the molecular-level mechanisms governing photocatalytic CO reduction.