Methane-selective nanoporous graphene membranes for gas purification.

The capability of functionalized graphene nanopores to efficiently separate methane from air is analyzed using density functional theory. We study the interaction between selected gas molecules and two finite model pores. Saddle point energies of the activated complexes are used to estimate transmission probabilities and selectivities as a function of temperature. We account for geometry distortions caused by the transient gas molecules and discuss the applicability and limitations of descriptions based on "molecular size" for the judgement of quasi-two-dimensional membranes.