Density functional theory(DFT)calculations and molecular dynamic(MD)simulations were performed to investigate the capability of graphene membranes with H-passivated nanopores for the separation of N2/CO2 gas mixtures.We found that the graphene membrane,H-pore-13,with its appropriate pore size of 4.06(A),can efficiently separate N2 from CO2.Different from the previously reported preferential permeation of CO2 over N2 resulting from size sieving,H-pore-13 can exhibit high N2 selectivity over CO2 with a N2 permeance of 105 GPU(gas permeation unit),and no CO2 was found to pass through the pore.It was further revealed that electrostatic sieving plays a cruical role in hindering the passage of CO2 molecules through H-pore-13.