Mesoporous Silica Skin on Clay Nanotubes for Carbon Capture

Amine-based adsorbents are considered extremely promising candidates for their efficacy in CO₂ capture. In this study, we explore the enhancement of CO₂ adsorption capacity through the development of a hierarchically porous material containing a mesoporous silica coating on halloysite nanotubes (HNTs), a naturally occurring clay material. The generation of a mesoporous MCM-41 skin on HNTs increases the surface area from about 60 to 400 m²/g while maintaining structural integrity. This significant increase in the surface area helps enhance amine loading. The synthesis of the MCM-41/HNT (MHNT) composite particles was achieved via an aerosol-assisted method, allowing rapid coating formation of a spindle-shaped skin on the HNT external surface and leading to a hierarchical porosity that supports both large pores in the HNT lumen and small pores in the MCM-41 coating. Poly-(ethylenimine) (PEI)-loaded MHNT adsorbents exhibit superior CO₂ adsorption capacities compared to adsorbents of PEI loaded into pristine HNT, with a 27% increase in the adsorption capacity. This work underscores the effectiveness of mesoporous skin in increasing amine adsorption efficiency on clay-based adsorbents, providing a pathway for the development of high-capacity, durable materials in carbon capture technologies.