Water pumping effect over the organic ions defined graphene oxide membrane impulses high flux desalination

Abstract

Graphene oxide (GO) membranes have shown great potential in ionic sieving from aqueous solutions. However, it remains challenging for GO membranes to exclude small ions with a large water flux. Herein, organic ions are confined onto the GO interlaminations to form a precisely restricted 2D channel size of 0.71 nm, which presents >99.9% NaCl rejections and high freshwater fluxes via the pervaporation method, both being orders of magnitude higher than that of common GO membranes. Theoretical calculations reveal that, apart from controlling the 2D channel size of GO by strong cation–/anion–π and π–π interactions, the organic ions act as vapor traps to remarkably shorten vapor diffusion distance and then as water pumps to significantly enlarge water permeability. It not only theoretically explains the low permeability over the common GO membranes with large 2D channels, but also experimentally demonstrates fast and complete desalination on the organic ions-GO membrane.