The surface density profiles provide crucial insights into the distribution of gases on the lattice near and away from the pore. CO2 populates the pore region to a significantly greater extent than the lattice region (Figure ). At 298 K, the CO2 population in the pore region is ∼ 1.9-2.5 times greater than the lattice region. At 423 K, the overall CO2 population decreases. Nevertheless, relatively higher adsorption on the pore is still observed compared to the lattice (Figure ). In contrast, a negligible population of O2 is observed in the pore region (Figure ). O2 adsorbs predominantly on the graphene lattice away from the pore. We infer that the high propensity of CO2 towards the pore region inhibits O2, contributing to the selective CO2 translocation. Similar observations have been made in crown-ether pores. However, pore dynamics and gating are not at play in these pore. Therefore, competitive adsorption of CO2 near the C=O group plays a crucial role in pore dynamics and selective gating. An adsorption peak in the density profiles is also observed on the permeate side (Figure ). This agrees well with the literature on transport dominated by surface or adsorbed-phase transport. In this case, after translocating through the pores, gases tend to first adsorb on the permeate side of graphene, and the final permeation event takes place when the gas desorbs from this adsorbed layer (Figure ,i, Figure ). PMF calculations confirm this, where a free energy valley on the permeate side was also observed (Figure ).