Additive-free Synthesis of House-of-card NaX Zeolite for Supporting Amine: an Efficient Adsorbent for SO2 Removal

The efficient adsorption of sulfur dioxide (SO2) is crucial for purifying exhaust gases, and zeolites are promising adsorbents due to their low cost and excellent stability. However, developing FAU-type zeolites with high adsorption capacities and selectivities remains challenging due to their narrow pores and limited adsorption sites. Herein, an additive-free synthesis strategy is proposed to facilely obtain NaX zeolites (X-HCL) with the house-of-card-like morphology. The hierarchical structure of X-HCL not only benefits the removal of SO2 through favorable spatial diffusion, but also promotes the loading of basic adsorption sites- [caprolactam] [tetrabutylammonium bromide] (CT) ionic liquid. The obtained CT/X-HCL adsorbent demonstrates remarkable SO2 adsorption capacity (10.58 mmol/g) and cyclic stability, as well as great selectivity of SO2/N2 (1673) and SO2/CO2 (219) due to the strong affinity of CT towards SO2. Moreover, co-feeding with water vapor benefits the adsorption of SO2 on CT/X-HCL owing to the enhanced chemisorption of hydrated CT for SO2. This research provides new insights into the construction of hierarchical zeolite for efficient adsorption and separation of SO2.