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

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.