A Multifunctional Calix[4]arene-based Lipophilic Clicked 2,6-bis-Triazolyl-Pyridine Ligand with High Actinide Selectivity and Radiochemical Stability for Spent Nuclear Fuel Treatment

The efficient separation of actinide (An) from lanthanide (Ln) cations in nuclear waste is crucial for sustainable nuclear energy production and effective radioactive waste management.1 One potential strategy to achieve this involves liquid-liquid extraction, where aqueous acidic metal solutions are treated with An-selective extractants dissolved in lipophilic solvents. In a previous study, the 2,6-bis[1H-1,2,3-triazol-4-yl]-pyridine chelating unit, functionalized with 2-ethylhexyl chains at the N1 position of the triazole ring (PTEH), demonstrated significant potential for this purpose, combining radiolytic stability, excellent extraction properties, and high An-selectivity.2 Based on these results, we designed and synthesized a calix[4]arene-based ligand (Calix-PTEH), which incorporates three chelating units to enhance both An-complexation efficiency and selectivity. This new ligand exhibits an excellent affinity to Cm(III), as determined by fluorescence titration, and the complex with Am (III) is characterized by 1D and 2D NMR spectroscopy. Preliminar extraction data reveal higher extraction efficiency when compared to PTEH