Fig. 4: Ion-selective transport from CMP-masked porous graphene membranes.

a Diffusion of Mg²⁺ through CMP-masked Gr membranes, and the inset shows the diffusion comparison of Mg²⁺ through the porous graphene membranes with and without the CMP mask layer. b Ion-ion separation performance of the membranes tested by different ions. The error bar is the standard deviation from at least three samples, and the center of each error bar represents the average data from these samples. c Long-term binary ion-sieving performance of the CMP-masked porous graphene membrane. d Trade-off relationship between Li⁺/Mg²⁺ selectivity and Li⁺ permeation rate of graphene membranes and state-of-the-art ion-sieving membranes reported in the literature, under concentration-driven single-ion process. The red pentagram marks the data obtained in the concentration-driven binary ion-sieving test. The red line is added to highlight the trade-off between ion permeation rate and ion-ion selectivity.