Nanoconfined Amine-Functionalized Silicone Oil Sorbents for Rapid CO2‑Capture

A novel CO2 sorbent system involving the confinement of aminated silicone oil-based liquid sorbents in hollow, microporous silica shells was investigated. In TGA experiments with three silicone oil sorbents (GAP-0, M′D′M′, and M3′T′), the nanoconfined materials exhibited initial CO2 sorption rates between 44 and 90 times faster than the corresponding unconfined, bulk liquid silicone oils. However, the liquids proved to be volatile at temperatures as low as 45 °C in the gaseous flow environment, resulting in a continuous decrease in CO2 sorption capacities over multiple sorption/desorption cycles. In contrast to their volatility in their CO2-free state, the nanoconfined sorbents exhibited excellent stability upon sorption of CO2, suggesting that the unique CO2 sorption-induced liquid-to-solid phase transition that characterizes these sorbents in their unconfined bulk form is not significantly altered through nanoconfinement. Overall, while the stability of these nanoconfined amine-functionalized silicone oils suffers from their high volatility at flue gas temperatures, the observed drastic acceleration of the CO2 sorption kinetics with very little energy penalty for the overall composite sorbent suggests that nanoconfinement is a flexible way to accelerate the sorption kinetics of liquid CO2 sorbents.