High-performance membranes have immense potential to improve carbon capture efficiency if they can be designed to yield a high CO2 selectivity and a high CO2 permeance. Nanoporous atomically thin membranes (NATM), particularly porous graphene, have attracted substantial attention. A single translocation event across the zero-dimensional pore determines selective transport. Attractive gas separation performance has been observed, with selectivity arising from relative mass, molecular size, and binding affinity differences. An accurate prediction of capture performance from graphene pores is needed to highlight the true potential of NATM. This will help design improved membranes for carbon capture.