Oxidation of graphene has been successfully used to incorporate semiquinone (C=O)-functionalized Å-scale pores, yielding attractive carbon capture performance. However, the true potential of such pores has remained unclear due to a lack of dedicated mechanistic studies. Herein, using molecular dynamics (MD) simulations, we show that C=O displays a remarkable molecular-interaction-dependent dynamic motion, leading to a distribution in PLD comparable to the size differences between CO2, O2, and N2. Dynamic open and closed pore states are observed in small pores, making impermeable pores CO2-permeable. The strong molecular interaction eliminates effusive transport, resulting in selective gating of CO2 from O2 and N2, even from large PLD pores expected to be nonselective. Finally, transition-state-theory calculations validated against MD simulations reveal the immense potential of porous graphene for carbon capture beyond the state-of-the-art membranes. These insights will inspire improved graphene membrane design, pushing the carbon capture frontier.