Intercalation of CO₂ Selected by Type of Interlayer Cation in Dried Synthetic Hectorite

Clay minerals are abundant in caprock formations for anthropogenic storage sites for CO₂, and they are potential capture materials for CO₂ postcombustion sequestration. We investigate the response to CO₂ exposure of dried fluorohectorite clay intercalated with Li⁺, Na⁺, Cs⁺, Ca²⁺, and Ba²⁺. By in situ powder X-ray diffraction, we demonstrate that fluorohectorite with Na⁺, Cs⁺, Ca²⁺, or Ba²⁺ does not swell in response to CO₂ and that Li-fluorohectorite does swell. A linear uptake response is observed for Li-fluorohectorite by gravimetric adsorption, and we relate the adsorption to tightly bound residual water, which exposes adsorption sites within the interlayer. The experimental results are supported by DFT calculations.