Synthesis and properties of pure and intergrown CHA/PHI zeolites from inorganic multi-cation colloidal suspensions

Abstract

The synthesis of zeolites using organic templates poses environmental and economic challenges, motivating the search for alternative approaches while still maintaining a high degree of control over the properties of the final crystalline product. In this study we expand the scope of multi-inorganic cation zeolite chemistry, exploring the synthesis and structural characterisation of pure nanocrystalline chabazite (CHA) and phillipsite (PHI), and intergrown CHA/PHI zeolites (Si/Al = 2.1–2.3). By applying the experimental reference intensity ratio (RiR) method to X-ray diffraction (XRD) data, we gained insights into the crystallisation pathways of the pure and intergrown phases. Detailed microscopy, textural and elemental analyses reveal the unique characteristics of zeolites obtained from simultaneous CHA and PHI crystallisation, resulting in different intergrown CHA/PHI particles depending on the varied synthesis parameters. CO₂ and N₂ adsorption analyses reveal low N₂ uptake in the intergrown samples, indicating their potential suitability for selective CO₂/N₂ gas separation applications. This work contributes to advancing sustainable and tailorable synthesis methodologies for zeolite-based materials for gas separation processes.