Unexpected Ion Sieving in Graphene Oxide Membranes

Ion sieving is significantly important in many fields such as life science, resource utilization, and environmental protection. However, unlike biological ion channels, realizing efficient ion sieving using two-dimensional (2D) membranes with artificial ion channels is severely restrained because of swelling. In this work, we demonstrated that graphene oxide membranes (GOMs) with the interlayer spacings controlled by K+ (K-GOMs) provide a remarkably enhanced ion sieving performance in mono-/multi-valent mixed ion systems, in which ion selectivity is more than 1 order of magnitude than that of untreated GOMs. The highest selectivity of Na+/Fe3+ for K-GOMs reached up to 159.1, which is superior to most of the state-of the art NF or 2D membranes, and the competitive permeation rate of Na+ ions still remained at 0.48 mol m(-2) h(-1). Additionally, the K-GOMs also showed an outstanding stability in the long-term test. Further, the K-GOMs also presented high selectivity for multi-valent/multi-valent mixed ion systems. Overall, this study gives a full picture of the excellent performance of K-GOMs based on the size effect for ion sieving and exhibits great value in real-world applications such as desalination, water treatment, battery, and even in life science.