Improving performance of mesoporous MOF AlTp impregnated with ionic liquids for CO2 adsorption

Abstract

In this work, the CO2 adsorption performance of metal–organic frameworks (MOFs) impregnated with ionic liquids (ILs) was studied using quartz crystal microbalance (QCM) at the temperature of 298.15 K and pressures up to 5 bar. The hybrid composites consist of aluminum terephthalate metal–organic framework (AlTp) impregnated of 1-butyl-4-methyl pyridinium and 1-butyl-3-methylimidazolium–based ionic liquids (ILs) with different anions, viz. tetrafluoroborate ([BF4]−), thiocyanate ([SCN]−), chloride ([Cl]−), and bromide ([Br]−). ILs-impregnated AlTp synthesized was characterized using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), the thermogravimetry analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. CO2 adsorption isotherms of the IL/AlTp composites and AlTp were measured to evaluate the ILs effect on the CO2 adsorption of the AlTp. Comparison of CO2 adsorption in ILs/AlTp with different anion ([Cl]−, [Br]−, [SCN]−, [BF4]−) reveals that CO2 adsorption in ILs/AlTp was increased in the order as: [BF4]− < [SCN]− < [Br]− < [Cl]−. The results show that [BMPyr][Cl]/AlTp the highest CO2 adsorption capacity, 2.6 times higher than that of AlTp at 5 bar and 298.15 K which helps to guide the logical design of new mixtures for gas separation applications. Also, adsorption/desorption test show that regeneration performance of [BMPyr][Cl]/AlTp is 96.53% after five consecutive cycles adsorption/desorption.