Effect of mono- and divalent extra-framework cations on the structure and the internal surface area

Chabazite (CHA), one of the most common zeolite framework types, has been studied extensively in selective gas sorption. This is due to the remarkable capacity of this zeolite to accommodate cations within the unique CHA framework. Here, we report a systematic study on a series of chabazite zeolites exchanged by divergent extra-framework cations with valence and atomic radius difference. The results showed that chabazite (KNa-CHA) was synthesised successfully from zeolite Y, and six chabazite zeolites including K-CHA, Cs-CHA, Ca-CHA, Ba-CHA, Sr-CHA and Zn-CHA were prepared from the parent chabazite by ion exchange. These samples were examined by numerous techniques and it was found that the difference in valence and size between extra-framework cations exert a significant effect on the abundance of these cations positioned in the framework, resulting in differing nitrogen sorption ability measured in the synthesised chabazite zeolites. These findings will help to understand the molecular sieve of the zeolite countercation which is a promising mechanism to selectively sequester and separate gases.

Figure. a) 27Al NMR spectrum of all chabazite zeolites. b) Nitrogen isotherms at 77 K of all chabazite zeolites

This work has been published in CrystEngComm