Fig. 2: Location of Cu²⁺ ions in the self-stratified aqueous-organic biphasic system.

a The concentration of Cu²⁺ in the [bmmim][Tf₂N] phase after equilibration with the CuCl₂-ZnCl₂ solutions. The inset shows the stratification of the 1 m CuCl₂−15 m ZnCl₂-based biphasic electrolyte. b The influence of the cations on the Cu²⁺ population in the organic phase. c Density profiles for Cu²⁺ and Tf₂N⁻ obtained by ICP‒OES and NMR, respectively. d A snapshot extracted from the simulation of the aqueous CuCl₂-ZnCl₂ solution/IL system. The green atom is Cl⁻, the blue atom is Cu²⁺, the red atom is O, the pink atom is H, the powder blue atom is N, the brown atom is C, and the yellow atom is S. e Density profiles for Cu²⁺ and Tf₂N⁻ at the interface of the biphasic electrolyte obtained by molecular dynamics simulations.