Mesoporous Polyamine Ionic Liquid Hybrids for Efficient Capture of Low-Concentration CO ₂ from Flue Gas

To address the growing demand for efficient low-concentration CO2 capture from flue gas, functionalized ionic liquid (IL) hybrids─integrating ILs’ intrinsic CO2-philicity (specific functional group-CO2 interactions) and porous supports’ structural merits (high specific surface area, tunable pores, robust framework)─have emerged as promising adsorbents. In this work, a kind of novel polyamine IL (PIL) hybrid with narrowly distributed mesopores and ultrahigh IL loading over 70 wt % was fabricated by immobilizing the PIL triethyltetramine trifluoromethanesulfonate ([TETA][TfO]) onto a hydrophobic resin (XAD) featuring wide mesopores and a small fraction of macropores. At 313 K, 70 wt % [TETA][TfO]@XAD exhibited a high CO2 adsorption capacity of 3.09 mmolCO2/g-adsorbent at 1 bar and 2.35 mmol CO2/g-adsorbent at 0.15 bar. Notably, under simulated humid flue gas conditions (15 vol % CO2/5 vol % H2O balanced with N2), the PIL hybrid still could maintain a relatively stable adsorption capacity of 1.31 mmol CO2/g-adsorbent, which is comparable to that under dry flue gas conditions (1.24 mmol CO2/g-adsorbent, 15 vol % CO2 balanced with N2). Furthermore, after three consecutive adsorption–desorption cycles, the PIL hybrid maintained structural integrity and stable CO2 adsorption performance without significant attenuation under both dry and humid environments. The superior CO2 separation performance was attributed to the chemical interactions between CO2 and multiple amino groups (one secondary amine as well as two primary amines) of [TETA]+, coupled with the synergistic effect of the in situ-formed mesoporous structures. This work provides a feasible strategy for the rational design and development of mesoporous PIL hybrids for the efficient capture of low-concentration CO2 from flue gas.