Insights into CO₂/N₂ separation through nanoporous graphene from molecular dynamics

We show from molecular dynamics simulations that porous graphene of a certain pore size can efficiently separate carbon dioxide from nitrogen with high permeance, in agreement with the recent experimental finding (Koenig et al., Nat. Nanotechnol., 2012, 7, 728-732). The high selectivity is reflected in the much higher number of CO₂ passing-through events than that of N₂ from the trajectories. The simulated CO₂ permeance is on the order of magnitude of 10⁵ GPU (gas permeation unit). The selective trend is further corroborated by the free energy barriers of permeation. The predicted CO₂/N₂ selectivity is around 300. Overall, the combination of high CO₂ flux and high CO ₂/N₂ selectivity makes nanoporous graphene a promising membrane for post-combustion CO₂ separation.