What Is the Smallest Zeolite That Could Be Synthesized?**

Abstract

Zeolites with a few unit cells are promising as catalyst and adsorbents. The quest to synthesize the smallest zeolites has recently resulted in 4 to 8 nm nanozeolites, about 2 to 4 unit cells. These findings pose the question of what is the smallest zeolite that could be obtained by hydrothermal synthesis. Here we address this question using molecular simulations and thermodynamic analysis. The simulations predict that amorphous precursors as small as 4 nm can crystallize zeolites, in agreement with the experiments. We find that interfacial forces dominate the structure of smaller particles, resulting in size‐dependent compact isomers that have ring and pore distributions different from open framework zeolites. The instability of zeolites smaller than 3±0.5 nm precludes a classical mechanism of nucleation from solution or through assembly of small nanoslabs.

Full‐scale modeling of chemical experiments

“…Using the above model, they reported a series of researches on zeolites' nucleation and crystallization dynamics process. For example, they described the unclassical nucleation process, which focuses on the effect of the stability of interphase, and they also confirmed the critical nucleus size [19–22] . Even though people can observe the crystallization process in tens of nanometers and several microseconds by using the coarse‐grained model, there are still limitations to the above models because they cannot describe the polymerization process of aluminosilicates.…”

“…For example, they described the unclassical nucleation process, which focuses on the effect of the stability of interphase, and they also confirmed the critical nucleus size. [19][20][21][22] Even though people can observe the crystallization process in tens of nanometers and several microseconds by using the coarse-grained model, there are still limitations to the above models because they cannot describe the polymerization process of aluminosilicates. For more macroscopic crystal structure evolution, Trueman studied the transformation of crystal grain structure by KMC, which agrees with experimental results.…”