Evidence of Facilitated Transport in Crowded Nanopores

Fluid transport in nature often occurs through crowded nanopores, where a number of phenomena can affect it, because of fluid-fluid and fluid-solid interactions, as well as the presence of organic compounds filling the pores and their structural fluctuations. Employing molecular dynamics, we probe here the transport of fluid mixtures (CO₂-CH₄ and H₂S-CH₄) through silica nanopores filled with benzene. Both CO₂ and H₂S are strongly adsorbed within the organic-filled pore, partially displacing benzene. Unexpectedly, CO₂/H₂S adsorption facilitates CH₄ transport. Analysis of the trajectories suggests that both CO₂ and H₂S act as vehicle-like carriers and might swell benzene, generating preferential transport pathways within the crowded pore. The results are useful for identifying unexpected transport mechanisms and for developing engineering approaches that could lead to storage of CO₂ in caprocks.