Titov Kirill, Zeng Zhixin, Ryder Matthew R, Chaudhari Abhijeet K, Civalleri Bartolomeo, Kelley Chris S, Frogley Mark D, Cinque Gianfelice, Tan Jin-Chong
Multifunctional Materials and Composites (MMC) Laboratory, Department of Engineering Science, University of Oxford , Parks Road, Oxford OX1 3PJ, United Kingdom.
Department of Chemistry, NIS and INSTM Reference Centre, University of Turin , via Pietro Giuria 7, 10125 Torino, Italy.
J Phys Chem Lett. 2017 Oct 19;8(20):5035-5040. doi: 10.1021/acs.jpclett.7b02003. Epub 2017 Oct 4.
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 high-resolution synchrotron infrared (IR) specular reflectance experiments to study the dynamic dielectric properties of a flexible MOF structure: bistable MIL-53(Al) that exhibits switching between a large pore (LP) and a narrow pore (NP) architecture. We show that 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.
新兴的纳米多孔材料，如金属有机框架材料（MOF），是下一代电子学和高速通信中极具前景的低介电常数电介质。迄今为止，MOF的介电特性研究较少，用于指导新材料设计和合成的实验数据非常有限。在此，我们展示了高分辨率同步辐射红外（IR）镜面反射实验在研究柔性MOF结构——双稳态MIL-53(Al)的动态介电特性方面的有效性，该材料在大孔（LP）和窄孔（NP）结构之间呈现切换。我们表明，通过增加用于压制MIL-53(Al)粉末的机械应力，可以改变多晶样品中LP:NP含量的比例。我们在约1至120太赫兹范围内量化了频率相关的介电常数，确定了所有介电转变与应力和相混合物的函数关系，展示了孔隙率如何改变MOF的介电特性。
