Amine-functionalized mesoporous silica derived from natural phyllosilicate for efficient CO2 adsorption

Amine-functionalized mesoporous silica is considered as one of the most promising solid amine adsorbents for post-combustion carbon dioxide (CO2) capture due to their high specific surface area, large pore volume and adjustable pore structure. However, the high costs associated with silica precursors and synthesis techniques of amine-functionalized mesoporous silica have extremely limited their practical applications. In this work, a facile and feasible approach was proposed to construct polyethyleneimine (PEI)-impregnated of Al-MCM-41 derived from natural flake-like kaolinite (FK) clay. The effect of PEI loadings and adsorption temperature on CO2 uptakes, adsorption/desorption kinetics and stability for Al-MCM-41/PEIx adsorbents were specifically discussed. The optimal Al-MCM-41/PEI (AP30) adsorbent exhibited a high CO2 uptake of 1.27 mmol/g at 75 °C and stable cyclic stability with a mere 1.1% decline per cycle over 10 adsorption-regeneration cycles, resulting from the unique ordered porous structure and spatial confinement effect of as-prepared Al-MCM-41 support to suppress excess PEI agglomeration and avoid blocking CO2 adsorption in the resultant adsorbents. The good PEI dispersions provided abundant CO2 affinity sites, which is beneficial to efficient CO2 diffusion and adsorption, and thus greatly improving the CO2 capture performances. This approach has enormous potential for cost-effective large-scale practical applications for CO2 capture and separation processes.