Molecular investigation on the mechanism of permselective transport of CO2/N2 mixture through graphene slit

• We investigated the effect of gap size of graphene slit on CO 2 and N 2 permeation. • We investigated the effect of gas-graphene interaction on CO 2 and N 2 permeation. • We explored the mechanism of CO 2 and N 2 molecules permeating through a graphene slit. • Increasing the adsorption capacity of graphene simultaneously enhances the N 2 permeation and the N 2 /CO 2 selectivity. Graphene-based laminates show great potential in gas separation, where graphene slit serving as an important part has significant effect on the gas transport. In this study, molecular dynamics simulations were performed to investigate the mechanism of the CO 2 and N 2 permeation through graphene slit. CO 2 was confirmed to permeate through the slit mainly via surface flux, thus the adsorption capacity of graphene largely determines the CO 2 permeability. Besides, the N 2 permeation is greatly dominated by direct flux, the contribution of which increases with enlarging the graphene slit. The adsorption capacity of graphene was modified to adjust the permselective transport of the CO 2 /N 2 mixture. Increasing the gas-graphene interaction obviously enhanced the N 2 permeation and retarded the CO 2 permeation. A triple enhancement of the gas-graphene attraction could achieve a quadruple increase of the N 2 /CO 2 selectivity. This work guides to improve the performance of graphene-based membranes in the CO 2 /N 2 mixture separation.