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.

This work presents a generic strategy to create a series of metal mercaptides complexes via coordination self-assembly between transition metals (Mn, Cu, Co, Fe, and Ni) and cysteine (Cys) by forming the sulfur-metal bridges. This strategy involves dissolving metal chlorides and Cys into deep eutectic solvents (DES), followed by the precipitation of metal mercaptides complexes (such as Cys-Mn) by adding water as an antisolvent, where DES serves as the solvent, shape directing, and capping agent, thereby preventing the formation of other metal impurities. Interestingly, the prepared complexes possess both laccase and peroxidase-like properties, allowing the design of a technique for the detection of L-3,4-dihydroxyphenylalanine (_L-DOPA) and uric acid, respectively. The prepared Cys-Mn can linearly oxidize _L-DOPA with its concentrations from 0.1 to 130 μM and the detection limit was calculated to be 75.5 nM. Additionally, the Cys-Mn can mimic the activity of peroxidase towards oxidization of o-phenylenediamine at neutral pH, allowing single-step and one-pot cascade reactions for visual and fluorometric measurements of uric acid (UA) that could work in the range of 0.2–500 μM UA with a detection limit of 0.06 μM and 0.054 μΜ, respectively. The assay was successful in detecting UA in serum and urine samples with relative standard deviation (RSD) ranging from 7.3% to 10.2% and 3.0%–8.5% respectively, suggesting that it may prove useful in medical diagnostic testing.