Zeolites are porous aluminosilicate materials widely employed in catalysis, adsorption, and separation technologies; however, directing their crystallization toward desired structural and functional properties remains a significant challenge due to the complexity of their synthesis. While the judicious selection of organic structure-directing agents (OSDAs) and/or heteroatom incorporation offer potential routes to design state-of-the-art zeolites, these strategies often come with economic, environmental, and practical drawbacks. As a more sustainable alternative, the use of metal ions as inorganic structure-directing agents (ISDAs) or growth modifiers has shown promise, though their influence on crystallization mechanisms remains poorly understood. Our group employs in situ high-temperature atomic force microscopy (AFM) to directly observe zeolite surface growth at near-molecular resolution. These studies reveal that zeolite crystallization primarily follows nonclassical pathways, such as particle attachment, with classical monomer-based layer-by-layer growth playing a lesser role.
In this presentation, we will discuss new insights into OSDA-free synthesis of zeolite faujasite (FAU) in the presence of metals (e.g., zinc), highlighting how the incorporation of these species affects crystallization dynamics and morphology, while also enhancing material stability and catalytic performance [1]. Additionally, we explore the accelerated, OSDA-free crystallization of chabazite (CHA) using a tailored combination of inorganic cations. We demonstrate how differences in ionic radii and solvation structures significantly influence crystal growth, offering a new approach to rational zeolite synthesis [2].
[1] Mallette, Adam J., et al. "Heteroatom manipulation of zeolite crystallization: stabilizing Zn-FAU against interzeolite transformation." JACS Au 2 (2022): 2295-2306
[2] Mallette, Adam J., et al. "Highly efficient synthesis of zeolite chabazite using cooperative hydration-mismatched inorganic structure-directing agents." Chemical Science 15 (2024): 573-583
