Interestingly, the surface flux pathway is also dominant for O2, a gas with a relatively weak interaction with the pore (67 and 55% at 298 and 423K, respectively). The dominance of surface flux and the competitive adsorption of CO2 has an important ramification, i.e., selectivity can be achieved from pores with pore size larger than the size of the molecule, as observed in this study for pore-16.