Interlayer functionalization of vermiculite derived silica with hierarchical layered porous structure for stable CO2 adsorption

Cyclic CO2 adsorption via solid amine adsorbents is widely considered as a feasible technology for CO2 mitigation from industrial flue gas. However, the high cost and rapid decline of adsorption capacity and insufficient cyclic stability limit their large-scale application. Herein, we demonstrated a facile and efficient interlayer functionalization approach, involving the synthesis of acid activated expanded vermiculite derived silica (AEV) support with hierarchical layered porous structure and the impregnation of PEI into the AEV support, to enhance CO2 adsorption capacity and cycle stability of AEV/PEI adsorbents. The optimal AEVP50 adsorbent exhibited a high CO2 uptake of 2.21 mmol/g at 75 °C and stable cyclic stability with a mere 1% decay after 10 cycles, owing to the superior hierarchical porous structure of synthesized AEV support. The interlayer functionalization of vermiculite was beneficial for enlarging interlayer volume and producing hierarchical porous structure and abundant Lewis acid sites, which could increase PEI loading content, form uniform amine distribution with less blocked pores/channels and enhance the interfacial interaction between PEI and AEV support. Furthermore, the interlayer spatial confinement effect significantly avoids the inactivation of functional amidogen during the regeneration stage. This strategy significantly enhanced the cyclic CO2 adsorption of AEV/PEI adsorbents through the interlayer functionalization of VMT, and is promising for various practical CO2 capture and separation processes.