Steering E/Z Linkage Modes in Isomeric Metal-Covalent Organic Frameworks for Photocatalytic Hydrogenation
The tuning of ligand linkage modes in porous crystalline materials to create isomers with varied properties is significant, yet remains rare in structural design and photocatalytic applications. Here, we investigate isomeric metal-covalent organic frameworks (MCOFs), MCOF-E and MCOF-Z, and reveal that specific construction struts lead to E/Z ligand linkage modes with distinct stacking structures, stimulated by temperature. These isomeric MCOFs exhibit different light absorption, charge transfer, and photocatalytic performance. Notably, MCOF-E achieves an aniline generation efficiency of 4.90 mM h−1 in nitrobenzene hydrogenation, with high conversion (~100%) and selectivity (>99%), outperforming MCOF-Z and other counterparts. Theoretical calculations indicate that MCOF-E possesses a narrower band gap than MCOF-Z, facilitating more efficient generation of photo-induced carriers, which accelerates reaction kinetics and significantly improves nitrobenzene hydrogenation efficiency. This work provides insight into the structure-function relationships of MCOFs and demonstrates the potential of isomerization as a strategy to optimize photocatalytic performance.