Trapped CO₂ in Carbon Nanotube Bundles

An infrared spectroscopic study of CO 2 that becomes permanently trapped in carbon nanotube bundles during thermolysis is reported. The temperature dependence of the ν 3 modes for trapped CO 2 is studied with two-dimensional infrared correlation spectroscopy. Computer simulations are used to extract the basic physics of trapped CO 2 and to make qualitative connections with changes seen in the infrared spectra. Experimental and simulated CO 2 adsorption studies point to a sequential filling of adsorption sites in opened nanotubes with interstitial sites preceding endohedral sites. The limited number of sites available to the trapped CO 2 species is used to facilitate a tentative assignment of vibrational peaks to specific sites in the nanotube bundles.