This work investigates the application of X zeolites for capturing CO2 from post-combustion flue gas. LiX and LiPdAgX zeolites were prepared by an ion-exchange method using 13X zeolite. X-ray diffraction analysis showed that all samples exhibited characteristic peaks of X zeolites, where the peak intensities increased in the order: LiPdAgX > LiX > 13X. The enhanced intensity of the diffraction peaks can increase the activity of the X zeolites and improve their adsorption performance. Scanning electron microscopy imaging showed that the intergranular pore canals of LiPdAgX zeolite were more concentrated. Pore structure analysis indicated that addition of Li+ to the 13X zeolite enhanced the specific surface areas and pore volumes of the zeolites. Among the 13X, LiX, and LiPdAgX zeolites, LiPdAgX showed the highest CO2/N(2)selectivity, where the difference in the CO2 adsorption capacity was due to differences in the number of adsorption sites and thermal conductivities of the X zeolites. The CO2 breakthrough tittle increased in succession for the 13X, LiX, and LiPdAgX zeolites. The CO2/N-2 separation factor of the LiPdAgX zeolite was twice that of the 13X zeolite at a CO2 concentration of 20 vol.%. The temperature variations during the adsorption process were used to determine the regeneration energy and adsorption capacity of the X zeolites. LiPdAgX zeolite required less energy for regeneration than 13X zeolite and MEA. After regeneration, the separation factor of LiPdAgX zeolite remained at 638 for 20 vol.% CO2 in the flue gas. Therefore, LiPdAgX zeolite can effectively capture CO2 from post-combustion flue gas to curtail the release of CO2 into the atmosphere. (C) 2017 Elsevier Ltd. All rights reserved.