Interlayer functionalization of silica nanosheets derived from natural clay for stable ionic liquids immobilization...

Supported ionic liquids (ILs) within porous supports are efficient carbon dioxide (CO₂) adsorbents and has become a promising alternative to solid amine adsorbents owing to their negligible volatility, excellent chemical/thermal stability, and non-corrosive nature. In this work, we explore the confinement of ILs within the hierarchical nanochannels of laminated silica nanosheets derived from low-cost vermiculite (AEV) for efficient CO₂ capture. A series of AEV/ILs (ILs confined within AEV) composites were synthesized via scalable wet impregnation approach, and the effects of several key factors, including ILs species, IL loading (10-50 wt%), adsorption temperature (25-65 °C), CO₂ partial pressure, and gas flow rate (50-100 mL/min), were systematically evaluated. Characterization data indicated that the ILs were successfully incorporated within the laminated porous network of AEV, leading to an intercalated confinement structure. Under atmospheric pressure and 35 °C in a 40 % CO₂/60 % N₂ flow, the AEV/BF₄-20 adsorbent (20 wt% 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]) loading within AEV) achieved a CO₂ uptake of 1.28 mmol/g, combined with rapid adsorption kinetics and stable recyclability, showing only an average capacity loss of 0.78 % per cycle over long-term testing. The hierarchical porous structure of AEV appears to promote efficient ILs dispersion and enhance CO₂ diffusion, thereby improving CO₂ capture performances. Furthermore, interactions between [BMIM][BF₄] and AEV nanosheets, together with multiscale adsorption pathways (surface, interlayer, intraparticle), are considered to synergistically enhance the CO₂ adsorption behavior. These low-cost raw materials, uncomplicated synthesis process and highly adsorption activity make AEV/ILs composites possible for large-scale production, showing great potential for various practical CO₂ capture and separation processes.