Interlayer functionalization of silica nanosheets derived from natural clay for stable ionic liquids immobilization and efficient carbon dioxide capture.

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.