An organic substance, hydroquinone is used to form clathrate compounds in order to identify separation characteristics of carbon dioxide in flue gas. Formed samples were analyzed by means of the solid-state 13C nuclear magnetic resonance (NMR) and Raman spectroscopic methods to examine enclthration behaviors of guest species. In addition, elemnetal analysis was also performed in order to evaluate separation efficiency of CO2 in a quantitative way. Based on the experimental results obtained, CO2 molecules are found to be captured into the clathrate compound more readily than N2 molecules. Moreover, because such preferential enclathration is even more significant at low pressure conditions, CO2 separation/recovery from flue gas can be achieved with minimizing additional energy cost for the technique. Experimental results obtained in this study can provide useful information on separation techniques of flue gas or selective separation of gas mixtures in the future.