Porous graphene membrane hosting C=O functionalized pore-16 outperforms state-of-the-art membranes (Figure ). In particular, a density ≥ 10 11 pores cm -2 , feasible in pore generation by oxidation, yields a very attractive CO2 permeance (>10000 gas permeation units or GPU, 1 GPU = 3.35 ´ 10 -10 mol m -2 s -1 Pa -1 ) accompanying large CO2/O2 and CO2/N2 selectivities. Such high performance is expected to reduce the energy input and cost of carbon capture, even from dilute point source emissions.