Enhanced Photocatalytic Efficiency and Structural Stability of Uranyl-Organic Coordination Polymers via the Semirigid Ligand

Uranyl-organic coordination polymers (UOCPs) have been demonstrated to exhibit photocatalytic activity, but highly stable UOCPs with excellent photocatalytic efficiency are rare. Herein, we present a series of UOCPs built by a semirigid benzimidazole-derived carboxyl ligand. By rationally designing the rigid and flexible sections of the ligand, we have obtained UO₂(HBDA)(OH)·H₂O (<b>UOCP-SU-1</b>), UO₂(HBDA)(H₂BDA)(NO₃)·H₂O (<b>UOCP-SU-2</b>), and UO₂(HBDA)₂ (<b>UOCP-SU-3</b>) with multiple spatial configurations under different conditions ([H₃BDA]Cl = 1,3-bis(4-carboxybenzyl)-1,3-dihydro-2<i>H</i>-benzo[<i>d</i>]imidazol-2-iminium chloride). The structural and photoelectrochemical properties of these UOCPs were systematically investigated, and the relationship between coordination structure and the photocatalytic performance for photooxidation of benzylamine to <i>N</i>-benzylenzoimide has been well established. The UOCP-SU-1 with bridged oxygen ligands in the coordination structure exhibits the best visible-light response and chemical conformational stability activity. Importantly, the UOCP-SU-1 can maintain its original crystal structures after 10 cycles of catalysis. This work provides a novel strategy for developing efficient uranyl-based photocatalysts for organic reactions.