Control of the Structural Charge Distribution and Hydration State upon Intercalation of CO into Expansive Clay Interlayers.

Numerous experimental investigations indicated that expansive clays such as montmorillonite can intercalate CO preferentially into their interlayers and therefore potentially act as a material for CO separation, capture, and storage. However, an understanding of the energy-structure relationship during the intercalation of CO into clay interlayers remains elusive. Here, we use metadynamics molecular dynamics simulations to elucidate the energy landscape associated with CO intercalation. Our free energy calculations indicate that CO favorably partitions into nanoconfined water in clay interlayers from a gas phase, leading to an increase in the CO/HO ratio in clay interlayers as compared to that in bulk water. CO molecules prefer to be located at the centers of charge-neutral hydrophobic siloxane rings, whereas interlayer spaces close to structural charges tend to avoid CO intercalation. The structural charge distribution significantly affects the amount of CO intercalated in the interlayers. These results provide a mechanistic understanding of CO intercalation in clays for CO separation, capture, and storage.