Many carbon-based membranes for gas separations can be made, but the degree that fundamental chemical bonding interactions in the membrane can be optimized for selective molecular separations remains an open question. For insight into this, we have computationally studied molecular diffusion of CH4, CO2, O2, and N2 through carbon membrane pore models using different levels of computational quantum chemistry theory. We study how chemical substitutions along the edge of the pore affect diffusion barriers. Our present work with a dispersion-corrected Kohn-Sham generalized gradient approximation exchange correlation functional indicates there is little interaction between a diffusing molecule and a moderately large, 54 atom pore lined with different chemical functional groups. Diffusion through a smaller pore produces more significant diffusion barriers ranging from 1–10 kcal/mol, depending on molecular orientation, pore functionality, and the diffusing molecule. Future work will consider the effects of different levels of quantum theory and different chemical functionalizations.

First principles modeling of gaseous molecules diffusing through graphene pores

255th National Meeting (2018)

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