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

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journal contribution
posted on 01.10.2019, 16:37 authored by Li-Wen Zeng, Kong-Qiu Hu, Lei Mei, Fei-Ze Li, Zhi-Wei Huang, Shu-Wen An, Zhi-Fang Chai, Wei-Qun Shi
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) ([H2bcbp]­Cl2), 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, 15, have been synthesized through hydrothermal reactions. Starting from uranyl ions and terephthalic acid (H2TP) and H2bcbp ligands, [(UO2)2(bcbp)­(TP)2]·3H2O (1) has a wave-shaped two-dimensional (2D) structure consisting of dinuclear units connected by terephthalate linkers and further supported by the longer H2bcbp ligands. [(UO2)2(bcbp)­(PA)2]·4H2O (2) has a zigzag chain of dimeric uranium units, and [(UO2)2(bcbp)­(bpdc)2]·5H2O (3) forms a one-dimensional ribbonlike structure. The 2D structures of [(UO2)­(bcbp)­(OH)­(H2O)]·Cl (4) and [(UO2)­(bcbp)­Cl]·Cl (5) are similar, both of which are constructed from dinuclear uranyl units and bcbp2– ligands. Furthermore, the performance for perrhenate removal of compound 4 with a cationic framework is assessed, and we found that compound 4 can efficiently remove ReO4 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.