The effect of the charges around the pore on the separation of H2S/CH4 mixture using a porous graphene membrane is investigated by molecular dynamics simulations. Due to the electrostatic interactions between H2S and membrane, the potential energy of H2S around the charged pore reduces. As a consequence, more H2S molecules accumulate around the pore and its selectivity is improved as well, while the permeation ratio of H2S is lower. The present study is valuable for designing the novel efficient membranes for the mixture separation. (C) 2014 Elsevier B. V. All rights reserved.