| Summary: | Emerging nanoporous materials, such as metal-organic frameworks (MOFs), are promising low-k dielectrics central to next-generation electronics and high-speed communication. Hitherto, the dielectric characterization of MOFs is scarce, with very limited experimental data for guiding new materials design and synthesis. Herein we demonstrate the efficacy of highresolution synchrotron infrared (IR) specular reflectance experiments, to study the dynamic dielectric properties of a flexible MOF structure: bi-stable MIL-53(Al) that exhibits switching between a large pore (LP) and a narrow pore (NP) architecture. We show the ratio of LP:NP content of a polycrystalline sample can be changed via increased mechanical stress applied for pelletizing the MIL-53(Al) powder. We quantify the frequency-dependent dielectric constants over ~1 to 120 THz, identifying all dielectric transitions as a function of stress and phase mixtures, showing how porosity modifies MOF’s dielectric properties.
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