Molecular dynamics simulations to examine the effectiveness of oxygen-functionalized graphene pores for CO2/O2 separation were performed using GROMACS 5.1.4 simulation package. simulation boxes were enclosed along the z direction by the porous graphene hosting 16 oxygenfunctionalized pores and a reflective wall made of a single-layer pristine graphene sheet. In order to generate the permeate side, another reflective wall was used such that the volume of the permeate side is the same as that of the reservoir. A similar simulation protocol has been employed previously to study gas separation and water evaporation from graphene nanopores. Owing to the hexagonal graphene lattice, a parallelepiped simulation box was used with a cross-sectional area of 142.18 nm 2 .