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

孔径小于2纳米的微孔材料是化学分离和催化的核心材料技术，越来越显示出储能应用的前景。微孔材料的高比表面积使其成为从二氧化碳捕获到用于离子传输或分离有毒物质和水过滤的膜的关键候选材料。然而，由于有限的分析工具，这些材料中的微结构(从微米到单个原子)的直接纳米级测量在很大程度上是缺乏的。关键的是，正是这些结构控制着基于工程材料的技术中的流体、气体和离子的传输。该项目将在纳米尺度上建立对微孔材料中化学传输的机理理解。该项目将涉及从沸石(微孔硅酸盐材料)和金属有机骨架(MOF)中制备和修改微孔材料，并设计分析显微镜工具来揭示相应的纳米级化学变化。该项目将涉及综合、材料加工、多种尖端电子显微镜和聚焦离子束技术，以及机器学习和人工智能指导的数据处理。沸石和MOF非常容易受到电子束的破坏，因此一个中心目标将是开发技术，在探测局部纳米级化学的同时，最小化和监测电子束下的变化。该项目将建立在最近的工作基础上，使用能量色散光谱对组成进行二维和三维成像，使用扫描电子衍射进行结构，以及MOF中的纳米级光学性质来确定金属中心的配位化学。通过使用光谱学、层析成像和衍射技术的组合，学生将开发分析科学工具，在纳米到原子尺度上确定微孔材料中金属位置和配位的位置和分布，这对催化和化学分离技术中的材料改进至关重要。

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.