Structuring ionic coordination microenvironments for selective Pt( IV )/Ir( IV ) separation via synergistic ion association

Abstract Selective Pt(IV)/Ir(IV) separation from spent proton exchange membrane (PEM) water electrolyzers remains challenging because of the similar coordination properties of their chloro‐complexes. Herein, ionic coordination microenvironments were engineered by combining the ionic liquid (IL) extraction systems to selectively extract Pt(IV) over Ir(IV) for the first time. The extraction system composed of 1‐aminopropyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([APMIM][Tf 2 N]) and Cyanex 923 (C923) achieved a single‐stage Pt(IV) extraction efficiency of 93.1% and separation selectivity of Pt(IV)/Ir(IV) of 369. Spectroscopic analysis, quantum chemical calculations, and molecular dynamics simulations revealed the so‐called “synergistic ion‐association mechanism” resulting in the selectivity separation of Pt(IV)/Ir(IV). Stronger hydration stabilizes [IrCl 6 ] 2− in the aqueous phase, whereas [PtCl 6 ] 2− preferentially associates with protonated [APMIM][Tf 2 N] and C923 to form a stable IL‐2H + ‐Pt(IV)‐C923 complex, promoting Pt(IV) transfer into the organic phase. These findings elucidate the molecular origin of Pt(IV)/Ir(IV) separation selectivity and provide theoretical guidance for designing task‐specific IL‐based extractants for platinum‐group metal recovery.