In Situ Synthesis of Uranyl-Imprinted Nanocage for Selective Uranium Recovery from Seawater.

An adaptive coordination structure is vital for selective uranium extraction from seawater. By strategy of molecular imprinting, uranyl is introduced into a multivariate metal-organic framework (MOF) during the synthesis process to guide the in situ construction of proper nanocage structure for targeting uranyl binding. Except for the coordination between uranium with four oxygen from the materials, the axial oxygen of uranyl also forms hydrogen bonds with hydrogen from the phenolic hydroxyl group, which enhances the binding affinity of the material to uranyl. Attributing to the high binding affinity, the adsorbent shows high uranium binding selectivity to uranyl against not only the interfering metal ions, but also the carbonate group that coordinates with uranyl to form [UO2 (CO)3 ]4- in seawater. In natural seawater, the adsorbent realizes a high uranium adsorption capacity of 7.35 mg g-1 , together with an 18.38 times higher selectivity to vanadium.