Electron microscopy for nano-chemistry of metal-organic frameworks and zeolites

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Microporous materials, with pores less than two nanometres in size, are central materials technologies for chemical separations and catalysis and, increasingly, show promise for energy storage applications. The high surface areas of microporous materials make them key candidates for applications from carbon dioxide capture to use in membranes for ion transport or separation of toxic species and water filtration. However, direct, nanoscale measurement of the microstructure in these materials (from microns down to individual atoms) is largely absent due to limited analytical tools. Critically, it is these structures that control the transport of fluids, gases, and ions for engineering materials-based technologies. This project will establish a mechanistic understanding of chemical transport in microporous materials at the nanoscale. The project will involve preparing and modifying microporous materials, drawn from zeolites (microporous silicate materials) and metal-organic frameworks (MOFs) and designing analytical microscopy tools to unveil the corresponding nanoscale chemical changes. The project will involve combining synthesis, materials processing, and multiple cutting-edge electron microscopy and focused ion beam techniques as well as machine learning and artificial intelligence-guided data processing. Zeolites and MOFs are highly prone to electron beam damage, and so a central objective will be the development of techniques that probe the local, nanoscale chemistry while minimising and monitoring changes under the electron beam.The project will build on recent work on the two- and three-dimensional imaging of composition using energy dispersive spectroscopy, structure using scanning electron diffraction, and nanoscale optical properties in MOFs to determine the coordination chemistry at metal centres. By using a combination of spectroscopy, tomography, and diffraction techniques, the student will develop analytical science tools to determine the positions and distribution of metal sites and coordination in microporous materials at the nano- to atomic-scale, crucial for materials improvements in catalysis and chemical separations technologies.