RII Track-4:NSF: Design of zeolite-encapsulated metal phthalocyanines catalysts enabled by insights from synchrotron-based X-ray techniques

非均相催化剂用于广泛的工业，包括化学和汽车行业，以使反应能够在温和的条件下进行，对所需产物具有更高的选择性。这些材料具有难以定义的复杂结构，因此难以进一步改进。在该项目中，将开发具有明确结构的模型催化剂，以确定这些材料的哪些方面有利于催化。使用世界上只有少数实验室可用的最先进的X射线技术（称为同步加速器），研究小组将精确确定这些材料在反应过程中的结构。这些测量在大学实验室是不可能的。通过这个项目，一名研究生和一名教授将获得执行这些测量和分析所得数据的专业知识，使研究人员能够与亚拉巴马州的不同合作者分享他们的知识。通过这些努力，该项目将增加亚拉巴马研究人员获得同步加速器X射线技术的机会，使该州在吸引联邦资金和私人投资进行科学研究方面更具竞争力。这个研究基础设施改善轨道-4 EPSCoR研究员项目将提供奖学金的助理教授和培训的研究生在亚拉巴马塔斯卡卢萨大学。这项工作将与SLAC国家加速器实验室的研究人员合作进行，合理设计多相催化剂所需的结构功能关系的发展需要在原子水平上详细了解无机固体的结构，包括金属原子的电子结构和原子之间的局部连接作为工艺条件的函数。实验规模的技术可以量化金属结合位点的数量，但不能识别和量化反应过程中它们的结构特征（氧化态，配位数和金属-配体键距）。这些测量的最佳技术是基于同步加速器的X射线吸收光谱（XAS），其中定量XAS数据是在工作催化剂上收集的，同时测量反应速率。该项目将通过深入参观SLAC国家加速器实验室（SLAC）的斯坦福大学同步辐射光源（SSRL），对沸石封装的金属酞菁配合物（MPC）的结构及其介导的化学反应有一个基本的了解。结合XAS与原位广角X射线散射（WAXS）和红外光谱测量允许监测两个主要结合位点的结构，限制它们的沸石孔的结构，以及催化过程中存在的中间体。研究团队将通过与这些技术领域的公认专家合作，获得XAS和WAXS方面的专业知识。在该提议中表征的材料避免了对于许多其他基于沸石、掺杂碳和MOF的催化剂不可避免的主要结合位点的局部构型中的不均匀性。这些催化剂将比溶液中的类似MPC络合物更稳定，从而允许在单位点催化剂上的气相化学。据我们所知，这将是首次使用八面沸石封装的MPC配合物，用于与N2 O的气相氧化反应，因此首次测量这些催化剂在该反应期间的原位或操作XAS光谱。通过了解这些材料在反应条件下的结构和稳定性，我们将描述多相单-该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

Heterogeneous catalysts are used in a wide range of industries, including the chemicals and automotive sectors, to enable reactions to proceed under milder conditions with higher selectivity towards desired products. These materials have complex structures that are difficult to define, and therefore difficult to further improve. In this project, model catalysts will be developed that have well defined structures, in order to determine which aspects of these materials are beneficial for catalysis. Using state-of-the-art X-ray techniques available only at a handful of laboratories in the world (known as synchrotrons), the research team will precisely determine the structures of these materials during reaction. These measurements are not possible in university laboratories. Through this project, a graduate student and a professor will gain expertise in performing these measurements and analyzing the resultant data, allowing the researchers to share their knowledge with diverse collaborators across the state of Alabama. Through those efforts, this project will increase access to synchrotron-based X-ray techniques for researchers in Alabama, allowing the state to be increasingly competitive in attracting federal funding and private investment in scientific research. This Research Infrastructure Improvement Track-4 EPSCoR Research Fellows project will provide a fellowship to an Assistant Professor and training for a graduate student at the University of Alabama Tuscaloosa. This work would be conducted in collaboration with researchers at the SLAC National Accelerator Laboratory.Development of structure function relationships necessary for rational design of heterogeneous catalysts requires detailed knowledge of the structure of inorganic solids at the atomic level, including of the electronic structures of metal atoms and the local connectivity between atoms as a function of process conditions. Laboratory-scale techniques can quantify the number of metal binding sites but cannot identify and quantify their structural features (oxidation states, coordination numbers, and metal-ligand bond distances) during reaction. The best technique for these measurements is operando synchrotron-based X-ray absorption spectroscopy (XAS), wherein quantitative XAS data are collected over a working catalyst while reaction rates are measured simultaneously. The project will develop a fundamental understanding of the structure of zeolite-encapsulated metal-phthalocyanine complexes (MPCs) and the chemistries they mediate by taking extended visits to the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC National Accelerator Laboratory (SLAC). Combining XAS with in situ wide angle x-ray scattering (WAXS) and infrared spectroscopy measurements allows monitoring of the structure of both the primary binding sites, the structure of the zeolitic pores that confine them, and the intermediates present during catalysis. The research team will gain expertise in XAS and WAXS by working with recognized experts in these techniques. The materials characterized in this proposal avoid heterogeneities in local configurations of primary binding sites that are unavoidable for many other zeolite-, doped-carbon-, and MOF-based catalysts. These catalysts will be more stable than analogous MPC complexes in solution, allowing for gas-phase chemistry over single-site catalysts. This will be the first use of faujasite zeolite encapsulated MPC complexes, to our knowledge, for gas-phase oxidation reactions with N2O, and thus the first measurements of in situ or operando XAS spectra of these catalysts during this reaction. By gaining an understanding of the structure and stability of these materials under reaction conditions, we will describe catalysis over heterogeneous single-atom complexes without distractions from variation in the local configuration of the primary binding sites and the pores that confine them.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.