Diffusion and separation of CH4/N-2 in pillared graphene were investigated by molecular dynamics. The pillared graphene with (6, 6) carbon nanotube (CNT) exhibited the higher diffusion and selectivity of CH4 over N-2 than that with (7, 7) CNT due to the cooperative effect of pore topological characteristics and interaction energy. The stronger interaction facilitated CH4 to enter CNT prior to N-2, and higher pressure promoted CH4 to pass CNT more easily. The relative concentrations profiles showed that CH4 reached equilibrium state faster than N-2 at low pressure. Our results highlight potential use of pillared graphene in gas purification and separation. (C) 2016 Elsevier B.V. All rights reserved.