Additive-free synthesis of house-of-card NaX zeolite for supporting amine: An efficient adsorbent for SO2 removal

The efficient adsorption of sulfur dioxide (SO 2 ) 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 SO 2 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 SO 2 adsorption capacity (10.58 mmol/g) and cyclic stability, as well as great selectivity of SO 2 /N 2 (1673) and SO 2 /CO 2 (219) due to the strong affinity of CT towards SO 2 . Moreover, co-feeding with water vapor benefits the adsorption of SO 2 on CT/X-HCL owing to the enhanced chemisorption of hydrated CT for SO 2 . This research provides new insights into the construction of hierarchical zeolite for efficient adsorption and separation of SO 2 .