Organic ion building blocks-assembled carboxyl ionic single crystals for ultra-selective and ultrafast uranium extraction

Uranium extraction from seawater (UES) is crucial for reducing nuclear fuel supply pressure and promoting the comprehensive utilization of marine resources. The successful implementations of UES engineering critically rely on the highly efficient sorbent materials with exceptional performance in binding uranyl ions. Herein, a universal and facile “organic ion building blocks self-assembly” strategy is established to realize a first class of carboxyl functionalized ionic single crystals, named BPTC-BPY-R (R = 1–6, the R corresponds to alkyl chain length modifier, e.g., R = 1 corresponds to iodomethane derivatives, R = 2 corresponds to bromoethane derivatives, etc.), derived from rationally designed viologen-derivatives with different alkyl chain lengths and polycarboxylic acid. This strategy effectively exploits the organic ion building block properties to achieve U(VI) adsorption based on the synergistic effects of anions (ligand interaction) and cations (electrostatic interaction). Notably, attributed to the special crystal stacking mode and higher specific surface area, the resulting BPTC-BPY-3 not only achieves ultrahigh selectivity for U(VI) adsorption with a partition coefficient of 3.998 × 10⁶ mL/g, but also possesses an ultrafast U(VI) adsorption kinetics and an uptake capacity of 686.8 mg/g within 2 min. More importantly, it realizes a U(VI) uptake capacity of 7.41 mg/g from natural seawater in 20 days. The designed material with ultra-selectivity, high capacity, ultrafast kinetics, and good recyclability exhibits a great promise for efficient U(VI) extraction from seawater.