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Description
The removal of trace plutonium (Pu) from uranium products and organic wastes during spent nuclear fuel reprocessing remains a critical challenge, resulting in excessive plutonium content in uranium products and waste organic liquid. Currently, most organic ligands with selective separation functions are lipophilic, while research on water-soluble highly selective ligands is relatively scarce, and there are also few reports on the single crystal of these ligands coordination with plutonium. Herein, a hydrophilic multiamide ligand, N,N,N',N'',N''-hexaethyl-nitrilotriacetamide (NTAamideC2), was synthesized and evaluated for its Pu(IV) back-extraction efficiency under harsh conditions. Systematic experiments revealed that NTAamideC2 achieved >99% Pu(IV) back-extraction rate within 15 minutes across a wide nitric acid concentration range (0–5 M), even with elevated dibutyl phos-phate (DBP ≤20,000 ppm). Remarkably, the separation factor (SFPu/U) reached 767 at 1.5 M HNO3, demonstrating excep-tional selectivity over uranium(VI). Spectrophotometric titration and DFT calculations confirmed the formation of 1:1 and 1:2 Pu(IV)-NTAamideC2 complexes, with log β values of 7.42 ± 0.01 and 13.23 ± 0.02, respectively. Single-crystal X-ray diffrac-tion analysis of {Pu2(H2O)2(NTAamideC2)42(NO3)(ClO4)7} revealed a nine-coordinated PuO7N2 geometry, where two NTAamideC2 molecules bind via six O and two N atoms. Compared to conventional agents (AHA/HSC), NTAamideC2 ex-hibited superior acid tolerance and selectivity, aligning with the CHON principle for sustainable nuclear waste management. This work provides a robust strategy for Pu(IV) removal in uranium purification cycles and advances fundamental insights into Pu co-ordination chemistry, offering significant potential for industrial nuclear fuel reprocessing.