Engineering mechanical and electrical properties of novel metal-organic framework composites

Lead Research Organisation: University of Oxford
Department Name: Engineering Science

Abstract

The project concerns the physical properties of an emergent class of nanoscale porous materials, called metal-organic frameworks (MOFs). We shall focus on understanding the basic mechanical characteristics of MOFs and their composite systems, using nanoindentation methods, dynamic mechanical analysis and large strain uniaxial deformation. Mechanical studies will be accompanied by electrical conductivity characterisation using DC and AC measurements and frequency sweep dielectric measurements. Aforementioned experiments will be performed in conjunction with theoretical studies, such as ab initio density functional calculations (molecular scale) and finite-element modelling (continuum scale).
Complex physico-chemical interactions and structure-property relationships will be investigated and established for representative MOF-based materials, thin films, monoliths and membrane composite systems.

MOFs are one of the most promising material because of their structural diversity, crystalline porosity, ease to produce and they can fulfil the growing demands of the microelectronics such as good chemical and thermal stability. As the size of the devices decreases into the integrated circuits, the probability of electron crossing to the other side increases that will lead to the noise. This can be reduced by using a MOF material that is an insulator and has a low dielectric properties. By doing this we can incorporate more active devices into the integrated circuit without having any cross talk and current leakage. There is only a few research going on in this direction but significant experimental and theoretical work is needed to improve it so that is can be used commercially.

This project falls within the EPSRC Engineering research area.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512333/1 01/10/2017 30/09/2021
2261373 Studentship EP/R512333/1 01/10/2017 30/09/2021 Arun Singh Babal
 
Description We achieved the following results during our investigation on dielectrics of MOF materials through this award:
1) We studied the dielectric property of HKUST-1 and MIL-100 powder pellets in the broadband frequency region (MHz and THz) for low-k applications. The activated MOF showed dielectric value well below the conventionally used silicon oxide and its compounds (k˜4). From our investigation we observed that dielectric constants of MOF materials can be modified through the application of pelleting pressure and temperature, indicating its dependency on the structural deformation, sample amorphization, and densification which are associated with the free volume and framework polarizability.
2) Additionally, we also investigated the effect of guest encapsulation on MOF's electronic properties. The increased temperature and pressure resulted in a steep increase in the dielectric properties. They could function as a tunable dielectric for development into high-frequency applications targeting photonic sensors and THz communication devices.
3) We also established a way to study dielectrics of the HKUST-1 MOF single crystal (?150 µm) for the first time. We also studied the effects of adsorption and desorption of different guest molecules (iodine, methanol, ethanol, and water). Unlike other guests that we studied, the adsorption of non-polar iodine resulted in a change in the optical property (turquoise to brown color) whereas the dielectric constant value remains unchanged. We carried out the frequency sweep from 100 Hz to 2 MHz and also studied the cyclic response of crystal for 1 MHz frequency. Using this technique, we can detect different vapors based on the changes in electronic properties.
4) Currently, we are carrying out experiments by drop-casting the MOF films on the surface of interdigitated electrodes (IDE electrode) and studying the changes in the electronic signal with adsorption and desorption of different guest vapors. The aim of this study is to build a solvent specific gas sensor.
Exploitation Route We studied the dielectric properties of the MOF material which is not well established yet. Due to the high porosity and tunability of these materials, we can modify the MOF properties to meet specific industrial requirements. Our study showed that MOF materials show a low-k dielectric property in the broadband frequency spectrum that can be utilized in miniaturizing the IC circuits by employing them as an interlayer dielectric material. Additionally, the MOF research community also gets benefits from our single crystal dielectric setup, which can study the electronic properties of different MOF single crystals. The setup can also be used to sense different vapors by their adsorption in the MOF pores resulting in the changed electronic property.
Sectors Chemicals,Electronics,Other

 
Description Researchers Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact This event was designed specifically for the research community in Engineering to come together and share their work. This was a great chance to find out what research activity there is in the Department.
Year(s) Of Engagement Activity 2019
 
Description 6th International Conference on Metal-Organic Frameworks (MOF 2018) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact It was an international MOF conference, where all the esteemed scientists related to this filed gathered and shared their research work. This helped me in planning my future plans.
Year(s) Of Engagement Activity 2018
URL https://www.aconf.org/conf_120906.html
 
Description Oxford Photonics Day 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact This was an event organized to generate awareness in researchers towards industrial applications. It helped us to understand what are the industrial demands and how to effectively present your research to others.
Year(s) Of Engagement Activity 2019