Molecular Investigation on the Mechanism of Permselective Transport of CO2/N2 Mixture through Graphene Slit

Abstract 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 CO2 and N2 permeation through graphene slit. CO2 was confirmed to permeate through the slit mainly via surface flux, thus the adsorption capacity of graphene largely determines the CO2 permeability. Besides, the N2 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 CO2/N2 mixture. Increasing the gas-graphene interaction obviously enhanced the N2 permeation and retarded the CO2 permeation. A triple enhancement of the gas-graphene attraction could achieve a quadruple increase of the N2/CO2 selectivity. This work guides to improve the performance of graphene-based membranes in the CO2/N2 mixture separation.