Structural Diversity of Bipyridinium-Based Uranyl Coordination Polymers: Synthesis, Characterization, and Ion-Exchange Application.

As well-known functional groups with excellent electro/photochromic and ion-exchange properties, bipyridinium motifs have been used in functionalized metal-organic coordination polymers, but they are still rarely applied to construct actinide coordination polymers. In this work, we utilized a bipyridinium-based carboxylic acid, 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium bis(chloride) ([Hbcbp]Cl), as the organic ligand to assemble with uranyl cations. By the introduction of different kinds of auxiliary ligands and adjustment of the pH, five novel uranyl coordination compounds, -, have been synthesized through hydrothermal reactions. Starting from uranyl ions and terephthalic acid (HTP) and Hbcbp ligands, [(UO)(bcbp)(TP)]·3HO () has a wave-shaped two-dimensional (2D) structure consisting of dinuclear units connected by terephthalate linkers and further supported by the longer Hbcbp ligands. [(UO)(bcbp)(PA)]·4HO () has a zigzag chain of dimeric uranium units, and [(UO)(bcbp)(bpdc)]·5HO () forms a one-dimensional ribbonlike structure. The 2D structures of [(UO)(bcbp)(OH)(HO)]·Cl () and [(UO)(bcbp)Cl]·Cl () are similar, both of which are constructed from dinuclear uranyl units and bcbp ligands. Furthermore, the performance for perrhenate removal of compound with a cationic framework is assessed, and we found that compound can efficiently remove ReO from an aqueous solution in a wide range of pH values. This work extends the library of viologen derivative-based uranyl coordination polymers, provides to some extent broader insights into actinide coordination chemistry of functionalized ligands, and may facilitate the ion-exchange applications of related coordination polymers.