Structural characterisation of subcritical carbon dioxide confined in nanoporous carbon by in situ neutron diffraction

In situ neutron diffraction measurements of adsorbed carbon dioxide in an ordered mesoporous carbon (CMK-1) have been carried out along an isotherm at 253 K and at a range of pressures up to 18 bar. The experiment has been performed with the aid of a novel high-pressure adsorption apparatus and the GEM diffractometer (ISIS, Rutherford Appleton Laboratory, UK). Diffraction measurements of bulk liquid carbon dioxide have also been carried out. The structure factors and the total differential correlation functions of the adsorbed carbon dioxide suggest that the confined fluid has liquid-like properties at all thermodynamic states studied; however, some subtle differences were observed pointing to enhanced adsorption because of the presence of micropores.