In-situ TEM liquid cell synthesis of metal-organic framework nanocubes

Researchers at the National Univerity of Singapore (NUS) and the University of Illinois at Chicago (UIC) have demonstrated direct evidence of the nonclassical nucleation pathways in the open-framework materials (MOFs) during the liquid crystallization process. Using Hummingbird Scientific’s Liquid TEM holder, they show that zeolitic imidazolate framework-8 MOF nanocrystals undergo a three-step pathway before fully crystallizing into cubic shape. The three-step process shown are 1) liquid-liquid phase separation into solute-rich and solute-poor regions, 2) direct condensation into an amorphous aggregate, and 3) crystallization to form cubic MOF (See Figure below). The results have been published in the prestigious journal, Proceedings of the National Academy of Sciences of the United States (PNAS).

In-situ TEM nucleation of cuboidal ZIF-8 nanocrystals demonstrating a three-pathway nucleation mechanism: (1) Phase Separation (2) Condensation, (3) Crystallization. Image Copyright © 2021 National Academy of Sciences.

Reference: Xiangwen Liu, See Wee Chee, Sanoj Raj, Michal Sawczyk, Petr Král, and Utkur Mirsaidov. “Three-step nucleation of metal–organic framework nanocrystals,” PNAS (2021).  Full paper

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