Hydroquinone (HQ) samples reacting with (CO2+N2) gas mixtures with various compositions at pressures ranging from 10 to 50 bar are analyzed using spectroscopic methods and an elemental analyzer. The results indicate that while both CO2 and N2 can react with HQ to form clathrate compounds, CO2 has higher selectivity than N2. In particular, at an operating pressure of 20 bar or greater, the CO2 content in the clathrate compound is 85mol% or higher regardless of the feed gas composition. Moreover, if a two-step clathrate-based process is adapted, CO2 at a rate of 93 mol% or higher can be recovered from flue gases. Thus, the clathrate compound described here can be used as a CO2 separation/recovery medium for CO2 in flue gases.