Computation-Aided Development of Next-Generation Extractants for Trivalent Actinide and Lanthanide Separation

The chemical similarities between trivalent actinides [An(III)] and lanthanides [Ln(III)] present a significant challenge in differentiating and separating them, which is a key step toward closing the nuclear fuel cycle. However, the existing separation approaches commonly suffer from demerits such as inadequate separation factors, limited stripping efficiency, and undesired coextraction. In this study, a novel unsymmetrical phenanthroline-derived amide-triazine (Et-Tol-CyMe₄-ATPhen) extractant was first designed and then screened with theoretical computation. Meanwhile, they were successfully synthesized by using a <i>de novo</i> construction method. As expected, Et-Tol-CyMe₄-ATPhen exhibited a favorable extraction ability for Am(III) and minimal extraction for Ln(III), thereby achieving an extremely selective An(III)/Ln(III) separation with a separation factor of over 280. Furthermore, Am(III) could be easily and effectively stripped from the loaded phases using dilute nitric acid. The underlying coordination mechanisms were thoroughly elucidated by using ¹H NMR, ESI-MS, UV-vis absorption spectrometry, photoluminescence spectrometry, and single-crystal X-ray diffraction. This work holds promise for addressing the current challenges in An(III)/Ln(III) separation and represents a pioneering endeavor in developing next-generation extractants from first-principles calculation.