(730a) In Situ Observation of Zeolite Crystallization By Multivariant Pathways

Zeolites are nano porous crystalline aluminosilicates with various commercial applications. To modulate the final physicochemical properties of the product during zeolite synthesis, it is essential to understand the underlying fundamental nucleation and crystal growth mechanism and the governing parameters. Despite significant efforts, these processes are not well understood owing in part to the inherent complexity of zeolite crystallization.^1,2 In this regard, our group has developed a protocol for solvothermal in situ atomic force microscopy (AFM) to capture the dynamics of zeolite surfaces at near molecular resolution under realistic growth conditions.Using this technique, we have identified methods to selectively control the pathways of growth and crystallization kinetics.^3,4

Here, we will present in situ AFM study of industrially relevant aluminosilicates (e.g., zeolite A and zeolite X) where we observe distinct growth regimes as a function of synthesis conditions. Zeolites A and X are used as commercial molecular sieves as well as an active catalysts in industrial reactions. We have used AFM to identify diverse modes of zeolite crystallization ranging from 3D gel-like islands to 2D layer-by-layer growth.⁵ Here we will discuss surface growth at low supersaturation where layer generation occurs via three distinct regimes. Our findings also reveal unique pathways of growth using inorganic and organic structure-directing agents with markedly different kinetics. Comparisons of zeolites A and X will highlight conditions leading to crystallize by either classical or non-classical mechanisms wherein an improved understanding of the dynamics of zeolite crystallization at high spatiotemporal resolution establishes a foundation for the rational design of porous materials.

References:

1. Davis et al.; Nature Materials 5 (2006) 400-408.
2. Anderson et al.; Nature 544 (2017) 456-459.
3. Lupulescu, A. I.; Rimer, J. D.; Science 344 (2014) 729-732.
4. Olafson et al., Chemistry of Materials 28 (2016) 8453-8465.
5. Kumar et al.; Nature Communications. 9 (2018) 1-19.