Charge controlled switchable CO2/N2 separation for g-C10N9 membrane: Insights from molecular dynamics simulations

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Using molecular dynamics simulations, we theoretically demonstrate that the CO2/N2 separation performance of g-C10N9 membrane can be controlled by introducing different charges into this membrane. It is found that neutrally charged g-C10N9 membrane is non-selective for CO2/N2 separation resulting from its large pore size. However, positively charged g-C10N9 membrane with charge density of 88 × 1013 e/cm2 exhibits 100% N2/CO2 selectivity, and the CO2/N2 selectivity of negatively charged g-C10N9 membrane with charge density of -60 × 1013 e/cm2 is more than four times higher than that of neutrally charged g-C10N9 membrane. Furthermore, it is shown that the CO2/N2 separation performance of charged g-C10N9 membrane is influenced by the number of CO2 molecules blocking at the pores and the binding energy between CO2 molecules and charged g-C10N9 membrane, which are determined by positive or negative membrane charge and charge density. Our results manifest that charge control is an excellent method for g-C10N9 membrane to realize switchable CO2/N2 separation.