CO$_{2}$ adsorption in a hierarchically structured carbon by SANS

This contribution investigated the high pressure adsorption behavior of CO$_{2}$ at T~$=$~296~K in hierarchically structured carbon using small-angle neutron scattering (SANS) technique. We observed a strong densification of CO$_{2}$ in micropores accompanied by non-monotonic adsorption-induced pore deformation. Liquid-like density of CO$_{2}$ confined in the micropores was reached with increasing pressure to 20~bar, which corresponds to the relative pressure of P/P$_{sat}\sim $0.3. At P~\textgreater ~20~bar, density of confined CO$_{2}$ approached a plateau. The size of micropores first increases with pressure, reached a maximum at 20~bar, and then decreased with further increasing pressure. A complementary SANS experiment carried out on the same microporous carbon saturated with argon that is neutron-transparent and non-adsorbing inert shows no deformation of micropores at pressures up to $\sim $200~bars. This result proved that the observed deformation of micropores in CO$_{2}$ was an adsorption-induced phenomenon, caused by the solvation pressure - induced strain and strong densification of confined CO$_{2\, }$in the micropores$_{.}$