Porous Graphene as the Ultimate Membrane for Gas Separation

We investigate the permeability and selectivity of graphene sheets with designed subnanometer pores using first principles density functional theory calculations. We find high selectivity on the order of 10(8) for H(2)/CH(4) with a high H(2) permeance for a nitrogen-functionalized pore. We find extremely high selectivity on the order of 10(23) for H(2)/CH(4) for an all-hydrogen passivated pore whose small width (at 2.5 A) presents a formidable barrier (1.6 eV) for CH(4) but easily surmountable for H(2) (0.22 eV). These results suggest that these pores are far superior to traditional polymer and silica membranes, where bulk solubility and diffusivity dominate the transport of gas molecules through the material.…