Molecular dynamics simulations of trihalomethanes (THMs) separation from water were performed using a functionalized nanoporous graphene under induced pressure. The simulated system included a functionalized graphene immersed in an aqueous solution of THMs. External pressure was applied to the system along the z axis of the functionalized nanoporous graphene. F-pore and I-I-pore terminated graphenes of different sizes were used. The results showed that a functionalized nanoporous graphene with a small diameter was impermeable to THMs. In contrast, a functionalized nanoporous graphene with a large diameter was shown to be permeable to THMs. The permeation of THMs and water molecules across the functionalized graphene was dependent on the chemical function of the pores, the size of pores, and the pressure. (C) 2015 Elsevier Ltd. All rights reserved.