Tuning the Hydrophobicity of Layer-Structure Silicates To Promote Adsorption of Nonaqueous Fluids: Effects of F– for OH– Substitution on CO2 Partitioning into Smectite Interlayers

The intercalation of nonaqueous fluids in the nanopores of organic and inorganic materials is of significant interest, particularly in the energy science community. Recently, X-ray powder diffraction and computational modeling results have shown that structural F– for OH– substitution in layered silicates makes them more hydrophobic. Here, we use grand canonical molecular dynamics calculations to investigate how increasing the F–/(F– + OH–) ratio of a prototypical layered silicate (the smectite Na-hectorite) impacts the intercalation behavior of CO2 and H2O at elevated temperature and pressure. At the conditions of this study (T = 323 K, P = 90 bar, water-saturated CO2), increasing F– for OH– substitution causes decreasing total CO2 + H2O intercalation, increasing CO2/(CO2 + H2O) ratios in the interlayer galleries, and an increasing energy barrier to CO2 and H2O intercalation. CO2 intercalation is the greatest at monolayer basal spacings, and the results support the idea that with Na+ as the exchangeable ...