Planar-coordination-induced precipitation by hydrazone-bridged clusters enables uranium-rare earth separation and...

Efficient uranium (U) recovery from nuclear wastewater is vital for the sustainable development of nuclear energy and the mitigation of environmental and biological risks posed by radioactive contaminants. In this study, we developed a series of hydrazone-bridged precipitants capable of selectively coordinating with uranyl ions in aqueous solution, inducing their precipitation and enabling simple, efficient solid-liquid separation. Guided by uranium's coordination preferences, 58 hydrazone-based ligands were systematically designed by tuning coordinating group types, site numbers and positions, and spatial configurations. Experimental evaluations and theoretical binding energy calculations identified the tetradentate ligand 2d as the most effective candidate, exhibiting high uranium uptake, excellent efficiency, and strong recyclability. Notably, ligand 2d maintained over 85 % uranium capture efficiency in the presence of 31 competing cations and 9 anions. In a uranyl-rare earth separation model, it achieved a separation factor up to 10⁶ and uranium purity above 99 %. In simulated nuclear wastewater, including high-fluoride systems, 2d consistently demonstrated > 95 % capture efficiency and adsorption capacities exceeding 300 mg/g. Single-crystal X-ray diffraction revealed the preferred coordination mode. Compared with conventional solvent extraction, this precipitation-based strategy offers superior selectivity, reusability, and environmental compatibility, highlighting its strong potential for large-scale uranium separation from complex nuclear waste streams.