Fig. 2: Ion sieving performance of MLM-EDTA.

a Schematic of the homemade U-shaped device used for ion permeation measurements. An encapsulated membrane (see Supplementary Fig. 39 for details) was fixed between feed and permeate chambers, magnetic rotors on both sides to prevent the effects of concentration polarization on the membrane surface. b Ions permeation rates through MLM and MLM-EDTA-1.5. c EDTA dependent K⁺/Mg²⁺ selectivity of MLM-EDTA membrane. d Schematic diagram of the interaction between EDTA molecules and alkali cations. e Schematic diagram of the interaction between EDTA molecules and alkaline earth cations. f Performance comparison of K⁺/Mg²⁺ selectivity vs K⁺ permeation rates for various membranes under similar testing conditions (see Supplementary Table 2 for details). Error bars represent the standard deviation of three measurements of a sample.