CO₂ capture with polyamine-based protic ionic liquid functionalized mesoporous silica

A mesoporous silica supported polyamine-based protic ionic liquid (PIL) sorbent has been prepared by impregnating tetraethylenepentammonium nitrate [TEPA][NO₃] onto the surface of SBA-15. This innovative hybrid adsorbent exhibits an excellent CO₂ adsorption rate in the rate-controlling step of 147 × 10^-3 mmol g^-1 s^-0.5, at least threefold better than other IL-functionalized and amine-modified support systems. Moreover, the adsorption capacity is enhanced by up to 2.15 mmol/g for the adsorbent at 333 K and 0.15 bar, which represents excellent performance under low CO₂ partial pressures. This adsorption performance can be ascribed to the synergistic effect of strong affinity between the PILs and CO₂ and large surface area of the support which favors the diffusion of the PILs and CO₂ molecules in its pores. In addition, density functional theory (DFT) calculations further reveal that CO₂ preferentially reacts with the secondary amine-N(2)H in [TEPA][NO₃] forming carbamate due to the high binding energy. The cyclic adsorption/regeneration experiment shows that nearly 90% of original CO₂ adsorption capacity of the adsorbent is restored by N₂ steam desorption at 373 K. Therefore this novel silica supported PIL system shows promise for CO₂ removal and recovery applications.