MIL-53(Cr)crystals were synthesized by the hydrothermal synthesis method

and then modified by ammonia vapor of different concentrations to obtain the modified materials NH3@MIL-53(Cr). The CO2 and water vapor isotherms on the NH3@MIL-53(Cr)were determined by means of the gravity method. Although the specific surface area of the modified materials NH3@MIL-53(Cr)became smaller compared to original MIL-53(Cr)

their CO2 adsorption capacities per unit surface area of adsorbent became significantly higher

following the order: NH3@MIL-53(Cr)-3#>NH3@MIL-53(Cr)-2#>NH3@MIL-53(Cr)-1#. In addition

Isotherms of water vapor on the modified samples NH3@MIL-53(Cr) were lower than those on the MIL-53(Cr)

suggesting significant improvement of hydrophobicity of the modified samples. The CO2 adsorption capacity of the NH3@MIL-53(Cr)-2# modified by using ammonia vapor of 1 mol·L-1 was the highest among the modified samples. More interestingly

the CO2 adsorption performance of the modified sample NH3@MIL-53 (Cr)-2# was significantly improved

while its CH4 adsorption performance was weakened

which would be helpful to enhance its selectivity for CO2/CH4 adsorption.