We report that Å-scale graphene pores decorated with C=O groups, generated from the oxidation of graphene, selectively gate CO2 largely driven by the dynamic behavior of pore edge C=O. The gas permeance and selectivity predicted from graphene pores are shown to be highly erroneous with the assumption of fixed PLD, indicating that fixed PLD calculation should be only considered for the cases with negligible molecule-pore interactions. Strong interactions between the pore edge functional group (C=O) with gas molecules control transport. These interactions open a seemingly impermeable pore or provides high selectivity from a seemingly nonselective pore. Therefore, capturing these interactions is extremely important for reliable gas flux and permeance predictions. TST-based rate calculation can be used to accurately predict gas flux and corresponding selectivity if the assumptions in the TST formulation are corrected to account for pore confinement effects. This allows one to rapidly predict gas permeance events even when the energy barrier for pore translocation is high, a scenario that greatly limits the applicability of MD simulations. These findings pave the way to understanding and predicting mass transport in realistic graphene pores and will guide the design of graphene membranes for molecular separation.