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

微孔材料，孔径小于2纳米，是化学分离和催化的核心材料技术，并且越来越多地显示出储能应用的前景。微孔材料的高表面积使其成为二氧化碳捕获、离子传输或有毒物质分离膜和水过滤等应用的关键候选者。然而，由于分析工具的限制，对这些材料的微观结构（从微米到单个原子）进行直接的纳米级测量在很大程度上是不存在的。至关重要的是，正是这些结构控制着流体、气体和离子在工程材料技术中的传输。该项目将在纳米尺度上建立对微孔材料中化学传输的机制理解。该项目将涉及制备和修饰从沸石（微孔硅酸盐材料）和金属有机框架（MOFs）中提取的微孔材料，并设计分析显微镜工具来揭示相应的纳米级化学变化。该项目将结合合成、材料处理、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引导的数据处理。沸石和mof非常容易受到电子束的损伤，因此一个中心目标将是开发探测局部纳米级化学的技术，同时最小化和监测电子束下的变化。该项目将以最近的工作为基础，利用能量色散光谱对成分进行二维和三维成像，利用扫描电子衍射对结构进行成像，并利用mof的纳米级光学特性来确定金属中心的配位化学。通过结合使用光谱学、断层扫描和衍射技术，学生将开发分析科学工具，以确定纳米到原子尺度上微孔材料中金属位点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.