Effect of Crystallite Size on the Flexibility and Negative Compressibility of Hydrophobic Metal-Organic Frameworks.

Johnson, Liam J W; Mirani, Diego; Le Donne, Andrea; Bartolomé, Luis; Amayuelas, Eder; López, Gabriel A; Grancini, Giulia; Carter, Marcus et al. · Nano Lett · 2023

basic_science · Level V

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Abstract

Flexible nanoporous materials are of great interest for applications in many fields such as sensors, catalysis, material separation, and energy storage. Of these, metal-organic frameworks (MOFs) are the most explored thus far. However, tuning their flexibility for a particular application remains challenging. In this work, we explore the effect of the <i>exogenous</i> property of crystallite size on the flexibility of the ZIF-8 MOF. By subjecting hydrophobic ZIF-8 to hydrostatic compression with water, the flexibility of its empty framework and the giant negative compressibility it experiences during water intrusion were recorded <i>via in operando</i> synchrotron irradiation. It was observed that as the crystallite size is reduced to the nanoscale, both flexibility and the negative compressibility of the framework are reduced by ∼25% and ∼15%, respectively. These results pave the way for <i>exogenous</i> tuning of flexibility in MOFs without altering their chemistries.