Ion-gated carbon molecular sieve gas separation membranes

Abstract

Membrane technology lies at the heart of many industrial gas separation processes and applications. Molecular sieving membranes that break the Robeson limit are desirable for energy-efficient gas separation. Herein, we report a facile strategy of directly integrating ionic liquids (ILs) into porous membranes. Particularly, the ILs form an ultra-thin layer on the carbon molecular sieve (CMS) membranes rather than penetrating into the pores, acting as a smart gate for gas entry to boost the selectivity. The hybrid membrane exhibits CO2 permeability >600 barrer and enhanced CO2/N2 selectivity >50, which surpasses the Robeson limit and shows potential in CO2/N2 separation process. Molecular dynamics simulations confirm the gating effect of the IL layer of molecular thickness. This work demonstrates a universal strategy to improve CMS membrane performance by creating an IL-membrane interface and tuning the ion-pore interaction.