Application of Functionalized Graphene Oxide Nanosheet in Gas Separation

Graphene oxide nanosheet (GONS) can be a suitable membrane for gas separation with high permeability and selectivity. Separation of N2/CO2 using functionalized GONS was investigated by molecular dynamics simulations. The simulated systems were comprised of two types of GONS with a pore in their center, N2 and CO2 molecules. The selectivity and permeability of these molecules can be controlled by drilling various pores with different sizes and functionalized factors in the edge of pores of GONS. Modification of pores using attaching functional groups to the carbon atoms at the edge of pores leads to very different outcomes. Using hydroxyl group at the edge of GONS pore (pore 1) leads to a substantial increase in the selectivity for N2 over CO2 and using fluoride atoms at the edge of GONS pore (pore 2) actually inverts the selectivity. When the pore size further increases, selective separation of molecules does not happen and both molecules propagate through the pores. Due to the interactions between molecules and membrane pores, the energy barrier for gas molecules in two pores was different, so that, the low energy barrier was in the pore 1 for N2 and in the pore 2 for CO2 molecules. If the energy barrier difference between two types of molecules is high, complete separation occurs. The present research is valuable for designing the novel GONS membranes for gas separation.