Development of amine-pillar[5]arene modified porous silica for CO2 adsorption, and CO2/CH4, CO2/N2 separation

Solid amine adsorbents with macrocycle are emerging as promising candidate for efficient CO2 adsorption due to their abundance of active sites, inherent cavities, and ease of encapsulation. Herein, a novel amine­pillar[5]arene functionalized porous silica adsorbent (EDA-P5S) was synthesized to investigate CO2 adsorption, the adsorption process of CO2 was executed using a fixed-bed (FD-2000) reactor. The dynamic adsorption capacities of EDA-P5S were 7.62 (0.46) and 7.72 (0.41) mmol/g for CO2/CH4 and CO2/N2, respectively, both the gas mixtures showed high separation selectivity. Subsequent research indicated that its porous structure facilitated the dispersion of amines and increased the exposure of active sites, thereby enhancing CO2 adsorption. Furthermore, the in-situ FTIR, 13C NMR spectra, and computational results collectively confirmed that the CO2 adsorption mechanism on EDA-P5S was consistent with the zwitterion mechanism. This work may provide a useful strategy for CO2 solid amine porous adsorbents to obtain high-purity CO2 by selectively removing CO2 from CH4 or N2.