CO2 adsorption behavior and mechanism of bifunctionalized amine-based protic ionic liquid/KIT-6 composites

Novel bifunctionalized amine-based protic ionic liquid/KIT-6 composite adsorbents for carbon dioxide (CO 2 ) adsorption have been prepared by impregnating amine-based protic ionic liquids of different types (tetraethylenepentamine nitrate, [TEPA][NO 3 ], or tetraethylenepentamine lysinate, [TEPA][Lys]) and concentrations (20, 30, 40, and 50 wt%) onto N-[3-(trimethoxysilyl)propyl]ethylenediamine-grafted KIT-6. These innovative hybrid adsorbents exhibited remarkable CO 2 adsorption performance and thermal stability. In particular, the adsorbent with 40 wt% [TEPA][Lys] loading exhibited the highest adsorption capacity at 90 ℃ (3.670 mmol·g −1 ), which was almost 5 times higher than that of the original carrier KIT-6 (0.850 mmol·g −1 ). This excellent adsorption performance can be ascribed to the synergistic effect of strong affinity between the amine groups and CO 2 and high porosity of the support. After five adsorption/desorption cycles, the CO 2 adsorption by the adsorbents demonstrated significant regeneration, and the saturated adsorption capacities of 2N-K6-P30 and 2N-K6-L40 were only 8.98 % and 7.77 % lower than those of the original ones, respectively. In addition, the infrared results revealed that CO 2 adsorption is a synergistic process of physical and chemical adsorption, in which chemisorption is dominated, and the CO 2 adsorption mechanism is consistent with the zwitterion mechanism. In conclusion, the bifunctionalized amine-based protic ionic liquid/KIT-6 adsorbents can be suggested as potential/recyclable materials for efficient removal of CO 2 from industrial flue gases after desulfurization.