We present molecular simulations to find the optimal conditions for the separation by adsorption of SF6 from a gaseous mixture with N-2, a mixture of key interest in electrical applications. The effect of pore size, pressure, and mixture compositions on the selective adsorption of SF6 was investigated by using Grand Canonical Monte Carlo simulations with simple fluid models and a simplified model of MCM-41. Simulations performed with multisite fluid models confirm that general trends are predicted using simple models, including a maximum in SF6 selectivity for pore diameters around 1.1 nm. Simulations were also performed using two atomistic models of zeolite-templated carbon (ZTC), FAU-ZTC, and EMT-ZTC, materials with average pore sizes close to 1.1 nm, obtaining high selectivities for both materials. Selectivities for FAU-ZTC are approximately four times higher than the best materials published for this mixture separation, opening excellent opportunities to use it for recovering SF6 from SF6/N-2 mixtures. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 962-974, 2011