The effect of the charges around the pore on the separation of H 2 S/CH 4 mixture using a porous graphene membrane is investigated by molecular dynamics simulations. Due to the electrostatic interactions between H 2 S and membrane, the potential energy of H 2 S around the charged pore reduces. As a consequence, more H 2 S molecules accumulate around the pore and its selectivity is improved as well, while the permeation ratio of H 2 S is lower. The present study is valuable for designing the novel efficient membranes for the mixture separation.