Modulating ionic liquid coordination microenvironments for lithium extraction: <scp>ePC</scp> ‐ <scp>SAFT</scp> modeling and molecular insights

Abstract This study proposes a novel strategy for enhancing Li + extraction from brines by modulating coordination microenvironments of ionic liquid (IL)‐based extractants using electron‐donating groups. The extractant system of 1‐butyl‐2,3‐dimethylimidazolium bis(trifluoromethylsulfonyl)amine ([BM 2 IM][Tf 2 N]) and tri‐isobutyl phosphate (TIBP) achieved a high single‐stage Li + extraction efficiency of 92.16% and separation selectivity of Li + /Mg 2+ of 519.12. The electrolyte perturbed‐chain statistical associating fluid theory (ePC‐SAFT) was employed to qualitatively predicted activity coefficients of Li + and Mg 2+ in the so‐called “organic‐inorganic composite electrolyte system” studied. The molecular‐level Li + extraction mechanism (i.e., the form of Li + ‐2TIBP‐2[Tf 2 N] − complex) was revealed by spectral analyses and quantum chemical (QC) calculations. It is found that enhancing Li + extraction by modulating coordination microenvironments is derived from two reasons of weakening both the cation‐anion electrostatic interactions within the IL and cation‐TIBP association, thereby promoting the exchange between IL‐cation and Li + overall. This work aims to provide a theoretical guidance for designing advanced Li + extractants.