CO2 and CO adsorption on MFI type zeolites with different SiO2/Al2O3 ratios (ZSM-5(30), ZSM-5(50), ZSM-5(280), and silicalite) were investigated in this study by a static gravimetric analyzer for pure isotherms at 30 degrees C, 65 degrees C, 100 degrees C, and 135 degrees C over the pressure range of 0-10 atm. Adsorption capacity of CO increases with decreasing SiO2/Al2O3 ratios within ZSM-5. The adsorption of CO2 for decreasing SiO2/Al2O3 ratios, showed stronger adsorption at lower pressures and at higher pressures, the highest capacity varied from ZSM-5(50) to ZSM-5(30). ZSM-5(280) was found to have the highest selectivity for CO2 within the widest range of pressures and temperatures tested.