Quest for the porosity-regulated high dielectric and conductive performance of MOF by introducing nanoparticles: Performance evaluation at elevated temperatures

Abstract

Metal-organic frameworks (MOFs) are among the novel materials that have drawn a lot of attention from the scientific and technological communities. There have been numerous reports of 3D MOFs in the scientific community, but due to distinct structural and electrical properties, scientists are particularly interested in zinc imidazole framework 8 (ZIF-8). Due to its characteristic low dielectric values, ZIF-8 is an excellent choice for low-dielectric applications. However, the incorporation of nanoparticles can increase the dielectric constant of ZIF-8. In this study, ZnO semiconducting nanoparticles are used as a filler of ZIF-8 due to their exceptionally high electron mobility, exciton binding energy, and wide band gap. We hypothesized that the incorporation of semiconducting nanoparticles (ZnO) inside ZIF-8 influences the porosity, pore size distributions, pore morphology, and interconnectivity of ZIF-8 which influences the polarization of pristine ZIF-8 and helps to increase the dielectric properties. ZnO has inherent ionic polarization which not only enhances the dielectric constant but also simultaneously decreases the dielectric loss which is essential for any dielectric materials. The dielectric constant was enhanced by 1.5 times after 5 wt% ZnO doping in ZIF-8 at room temperature and the enhancement was nearly five times at 150 °C. Simultaneously the dielectric loss decreases after ZnO doping compared to pristine ZIF-8. The tailoring of porosity, the number of pores, the presence of defects and oxygen vacancies are responsible for the modulated dielectric properties. The conductivity of ZIF-8 can also be tuned by the nanoparticles incorporation which indicates the larger production of drift electrons inside MOF in the presence of nanoparticles. The detailed morphological characteristics confirm the interaction between ZnO and ZIF-8. The result is a thorough understanding of the intrinsic and extrinsic electrical properties of ZIF-8 composites for future generations of technology. This work aimed to exploit possibilities of MOF towards high dielectric constant and low loss material by simple nanoparticle incorporation.