Decisive role of pore edge termination in determining the CO2 selectivity of Å-scale pores in graphene

Zero-dimensional pores in graphene hold significant promise for carbon capture. However, the impact of pore-edge functional groups on carbon capture performance remains limited. Herein, using molecular dynamics simulations and potential of mean force calculations, we demonstrate that pore-edge groups can dictate whether an Å-scale pore exhibits selectivity or not. We show that oxygen-functionalized (O-pores) enable highly selective CO2/O2 transport, whereas similarly-sized hydrogen-terminated pores (H-pores) are non-selective. This contrast stems from drastically different CO2–pore interactions in the two pores. In O-pores, CO₂ molecules strongly adsorb and remain at the pore mouth for up to a nanosecond, while in H-pores, CO2 residence times are up to two orders of magnitude shorter. Next, we develop a transition-state-theory model that accurately predicts gas transport through both O- and H-functionalized pores. This is achieved by correcting the velocity distribution at the transition state to account for molecule–pore interactions. The resulting velocity-corrected TST model enables accurate and generalizable predictions of gas translocation, independent of pore-edge functional groups. These insights not only provide a robust theoretical basis for rational membrane design but also highlight the advantage of oxidative pore formation protocol, which yields O-pores, for carbon capture membranes.