Soft-Pillared@Magadiite: influence of the interlayer space and amine type on CO₂ adsorption

Layered silicates are versatile materials that can be grafted with different organosilanes for several applications. Despite this, there are few studies on the use of layered silicate-based materials in CO₂ adsorption. In this regard, the present study describes the synthesis of organo-magadiite followed by simultaneous grafting with two organosilanes ((3-glycidyloxypropyl)trimethoxysilane (GPTS) and N¹-(3-trimethoxysilylpropyl)diethylenetriamine (TMSPETA)) to prepare an adsorbent labeled Soft-Pillared@Magadiite. The adsorbents were characterized through XRD, ¹³C- and ²⁹Si-NMR, TGA/DTG, and elemental analyses of carbon, hydrogen, and nitrogen (CHN). The results suggest that this adsorbent has an expanded interlayer space (3.05 nm) that is larger than the interlayer space when the layered material is grafted with the organosilanes separately, and it may display improved CO₂ adsorption. The CO₂ adsorption was evaluated by TGA, CO₂-TPD, and DSC. Moreover, the adsorption isotherms were fitted using a pseudo-second order, a fractional order, and Avrami models. The optimum adsorption temperature of Soft-Pillared@Magadiite was 25 °C, and the adsorption capacity and efficiency were 0.36 mmol g^-1 and 0.15, respectively, obtained using 5 vol% CO₂ in He for 3 h. The CO₂-TPD shows that the desorption of CO₂ occurs below 90 °C, and from DSC, it is found that thermodynamic parameters, specifically sensible heat and heat of regeneration, are low as compared to those of aqueous MEA solution; the current technology indicates that Soft-Pillared@Magadiite has a good potential for CO₂ adsorption.