The importance of nanopore structures of carbons is shown in terms of interaction potential for various molecules including supercritical gases such as H2 and CH4. The key factors for adsorption of supercritical H2 and CH4 are shown for single wall carbon nanohorn, single wall carbon nanotube, and double wall carbon nanotube. The cluster formation of molecules is a key process for water adsorption on hydrophobic carbon nanopores. The X-ray absorption spectroscopic examination elucidates an explicit dehydration structure of ions confined in carbon nanopores.