Hydroxyl-functionalized polyethyleneimine on graphene/vermiculite-derived porous silica nanosheets to achieve highly stable CO2 capture

Solid amine adsorbents play an important role in separating CO 2 from flue gas and can be used in post-combustion CO 2 capture. However, their effective regeneration capabilities and long-term stability remain significant challenges. Herein, a hydroxyl-functionalized polyethyleneimine on graphene/vermiculite-derived porous silica nanosheets with good structural tunability was reported as a solid amine adsorbent. The optimized adsorbent possesses a high working capacity (1.50 mmol/g) and long-term stability in practical temperature swing adsorption processes. After 20 adsorption-desorption cycles, the adsorption capacity decreases by only 3.2%, demonstrating good cyclic stability. The formation of hydrogen bonds between the hydroxyl groups of glycerol and the amino groups of polyethyleneimine significantly reduces the irreversible conversion of amine groups to urea groups, thereby greatly enhancing the cycling stability of the adsorbent. The incorporation of graphene enhances the thermal conductivity of porous silica nanosheets by 42.8%, allowing for rapid thermal transmission and preventing local overheating during the CO 2 adsorption process. The combined strategy of amine functionalization and porous support design in this work offers an effective approach to improving the cycling stability of solid amine adsorbents.