Design and Fabrication of Functional Microporous Materials

Lead Research Organisation: Imperial College London
Department Name: Department of Chemical Engineering

Abstract

Separation processes critically determine the efficiencies in chemical, energy and environmental processes, such as gas separation for large-scale energy and oil & gas industry (natural gas purification, CO2 separation, air separation, hydrocarbons separations in petrochemical industry, etc.), chemical separations, and water desalination and purification. We are developing a variety of synthetic and fabrication techniques for formation of membrane and nanofilms, for example, solution processing, interfacial polymerization, and mixed matrix membranes. We then perform extensive characterisation of the membranes to understand their structure and relationships with separation performance, and ultimately aim to develop more permeable and selective membranes for gas and chemical separations and commercialization in industry.

Publications

10 25 50

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512540/1 01/10/2017 31/03/2022
1966627 Studentship EP/R512540/1 01/10/2017 31/03/2022 Anthony Richard Houghton
 
Description Ellipsometry is a powerful technique that measures the change in polarisation of light as it reflects from a thin-film material structure. Through modelling and data processing, the optical properties (ie complex refractive index) and thickness of the thin-film can be measured. In combination with an environmental chamber, this instrument can measure the change of refractive index and or thickness upon exposure to different partial pressures of water or organic solvents. This leads to a method called Ellipsometric porosimetry (EP), where upon adsorption and desorption of such solvent vapours on a porous thin-film, the refractive index of the film changes. This can be converted to the uptake of the film and properties such as the diffusion kinetics, isotherms, surface areas and pore-size distributions (PSD) can be calculated. This is currently being investigated on a range of novel porous thin-film structures, in collaborations with other universities and institutes, such as silica, titania, indium and metal-organic framework thin-films, which have applications in catalysis, sensors, electronics, membranes and adsorbents. The main findings so far are on the silica and titania:
The porous silica thin-films by University of Southampton are prepared by "electrochemically assisted surfactant assembly" to fabricate thin-films of different pore sizes using surfactants of different chain lengths. Ellipsometric porosimetry has shown so far that increasing the surfactant chain length increases the pore size, as expected. This has been done in conjunction with X-ray techniques, however, the X-ray method becomes limited to calculating pore sizes as the length of the surfactant increases beyond a certain point, therefore EP is being used to unravel the pore sizes.
The porous titania thin-films are prepared with different thicknesses by spin-coating using a suspension of nano particles. The thickness is increased using a "layer by layer" format, where one layer is coated onto another. The change in thickness was then explored by SEM and ellipsometry. Each layer consisted of approximately 5 nm. The surface area/porosity and PSD of the different thin-films are also being investigated. These are noteworthy properties to know as porous titania is a commonly used material for catalysis or electrodes.
Other types of porous thin-films are still being investigated. There is also interest at looking how in-situ ellipsometry can be used to investigate the swelling of polymer films when exposed to water or organic solvent vapours. This includes both porous and non-porous polymers such as Polymers of Intrinsic Microporosity and Polyvinylpyrrolidone, respectively.
Exploitation Route Porous thin-films of novel materials such as MOFs, COFs, POCs, PIMs etc. has been growing field of research. In-situ ellipsometry offers a fast and non-destructive method to characterise porous thin-films to find out properties such as the diffusion kinetics, isotherms, surface areas and pore-size distributions. It is commonly used in both academia and industry to measure thin-film thickness, but not so much on porosity and swelling measurements. Shedding light into this technique would be important for research in many fields to characterise thin-films at different environmental conditions. Another key area of interest is also the stability of some thin-films when exposed to solvent vapours, in particular water. Whether it be biological films or organic solar cells, this technique would be very useful in understand how to optical properties and or thickness changes with environment.
Sectors Chemicals,Construction,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology