Temperature-Dependent Mechanical Properties of a Metal-Organic Framework: Creep Behavior of a Zeolitic Imidazolate Framework-8 Single Crystal.

Zeolite Imidazole Framework-8 (ZIF-8) with a robust structure and high thermal stability is a strong candidate to act as the catalyst matrix for various chemical applications, especially for those at higher temperatures, like hydrogenation. In this study, the time-dependent plasticity of a ZIF-8 single crystal was explored by a dynamic indentation technique to explore its mechanical stability at higher temperatures. The thermal dynamic parameters for the creep behaviors, like activation volume and activation energy, were determined, and possible mechanisms for the creep of ZIF-8 were then discussed. A small activation volume implies the localization of the thermo-activated events, while high activation energy, high stress exponent , and weak dependence of the creep rate on temperature all favor pore collapse over volumetric diffusion as the creep mechanism.