Restricted adsorption of carbon dioxide gas in fluorinated single-walled carbon nanotubes

Single-walled carbon nanotubes were fluorinated between 298 and 473 K using elemental F-2, and their adsorption properties were investigated through N-2 and CO2 adsorption measurements. Interestingly, a low-pressure adsorption/desorption hysteresis phenomenon was observed for the CO2 adsorption/desorption isotherms of the fluorinated nanotubes. This remarkable adsorption/desorption hysteresis may be attributed to restricted access to the inner pores of the nanotubes due to the presence of fluorinated pore gates. Diffusional limitations caused by such pore blocking effects are therefore discussed as the origin of the hysteresis. This low-pressure hysteresis may provide an insight into adsorption in the fluorinated pores, which is of particular interest for gas adsorption technologies.