First Cationic Uranyl–Organic Framework with Anion-Exchange Capabilities

By controlling the extent of hydrolysis during the self-assembly process of a zwitterionic-based ligand with uranyl cations, we observed a structural evolution from the neutral uranyl–organic framework [(UO2)2(TTTPC)­(OH)­O­(COOH)]·1.5DMF·7H2O (SCU-6) to the first cationic uranyl–organic framework with the formula of [(UO2)­(HTTTPC)­(OH)]­Br·1.5DMF·4H2O (SCU-7). The crystal structures of SCU-6 and SCU-7 are layers built with tetranuclear and dinuclear uranyl clusters, respectively. Exchangeable halide anions are present in the interlaminar spaces balancing the positive charge of layers in SCU-7. Therefore, SCU-7 is able to effectively remove perrhenate anions from aqueous solution. Meanwhile, the H2PO4–-exchanged SCU-7 material exhibits a moderate proton conductivity of 8.70 × 10–5 S cm–1 at 50 °C and 90% relative humidity, representing nearly 80 times enhancement compared to the original material.