Amino Acid Decorated\nPhenanthroline Diimide as Sustainable\nHydrophilic Am(III) Masking Agent with High Acid Resistance

Hydrophilic actinide masking agents are believed to be\nefficient\nalternatives to circumvent the extensive hazardous organic solvents/diluents\ntypically employed in the liquid–liquid extraction for nuclear\nwaste management. However, the practical application of hydrophilic\nligands faces significant challenges in both synthetic/purification\nprocedures and, more importantly, the acid resistance of the ligands\nthemselves. Herein, we have demonstrated the combination of phenanthroline\ndiimide framework with a biomotif of histidine flanking parts could\nachieve efficient separation of trivalent lanthanides/actinides (also\nactinides/actinides) under high acidity of over 1 M HNO<sub>3</sub>. This approach leverages the soft–hard coordination properties\nof <i>N, O</i>-hybrid ligands, as well as the energetically\nfavored imides for metal coordination and the multiple protonation\nof histidine. These factors collectively contribute to the synthesis\nof an easily accessible, highly water-soluble, superior selective,\nand acid-resistant Am­(III) masking agent. Thus, we have shown in this\npaper, by proper combination of synthetic <i>N, O</i>-hybrid\nligand with amino acid, trivalent lanthanide and actinide separation\ncould be efficiently fulfilled in a more sustainable manner.