Metal-organic framework materials for low-k dielectrics and selective sensing applications

Thesis

Metal-organic frameworks (MOF) are fascinating hybrid materials, gained widespread attention from the scientific community since their emergence about three decades ago. The high porosity and tailorability of MOF structures make them an ideal candidate material for both low-k dielectrics and electrical sensing applications. In this work, an in-depth study on different MOFs was carried out to explore the influence of host-guest interaction and external stimuli including pelleting stress, operating temperature, and frequency, on MOF dielectrics. Additionally, a mechanism was proposed to identify the exceptional MOF materials for target guided electrical sensing and optimise the sensor preparation parameters to enhance its selectivity and sensitivity to revolutionise the conventional electrical sensors. Both polycrystalline (in the form of pellets) and single-crystal MOF samples were studied to gain a deeper insight into both areas.

First, the influence of different external stimuli (temperature, pressure and amorphization) on broadband dielectrics (Hz-MHz and THz) was investigated for both HKUST-1 and MIL-100 MOF systems, to gain a greater understanding of structure-property relation. Secondly, by leveraging the different synthesis approaches, the role of guest molecules was also analyzed for both the polycrystalline powder pellets and single-crystal HKUST-1 MOF systems in the Hz-MHz frequency range. The single-crystal study, which is independent of pelleting pressure and free of grain boundary influence, provided a greater insight into the MOFs intrinsic properties. Thirdly, the impact of host-guest interaction dependent electrical response was materialised in the form of proof-of-concept electrical sensor applications.

Overall, this work consolidates the candidacy of MOFs as an efficient low-k material and also expands its future portfolio to the realm of ultra-trace highly sensitive electrical sensing.

Authors: Babal, AS

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Interdigitated Electrodes; Impedance Response; Dielectric Response; Metal-Organic Frameworks; Iodine Sensing
• Subjects: Functional Materials; Porous Materials; Engineering Science; Electrical Sensors; Materials Chemistry