Collaborative Research: Tailoring the Catalytic Properties of Pd Single Atoms Using Covalent Organic Frameworks

催化剂广泛用于工业过程中，以提高能源效率并将化学反应导向所需的产物。 该项目研究了一类重要的工业反应-选择性氢化-的新型催化剂设计，用于许多应用，如塑料，香料和药品的生产。 贵金属钯（Pd）广泛用于选择性氢化反应。 该项目旨在最大限度地利用孤立原子形式的贵金属，并通过将其锚定到共价有机框架（COF）来调整其特性，COF是高度结晶的多孔材料，具有金属原子的特定结合位点。 研究人员将使用一套基于实验室和同步加速器的表征技术合成和表征催化剂。 将测试催化剂用于乙炔选择性氢化成乙烯，以确定结合位点如何影响Pd原子的活性和选择性。 除了研究之外，该项目还包括对研究生和本科生的教育，以及两个机构之间研究人员的交叉培训，并集中努力增加催化科学中代表性不足的群体的参与。该项目旨在使用共价有机框架（COF）作为支持体/配体来定制Pd单原子的性质，因此避免了与传统的用于乙烯半氢化的金属氧化物负载的纳米颗粒催化剂相关的活性和选择性之间的折衷。 重点领域包括1）COF结合位点和二级配体对Pd电子性质的影响，2）氢活化，3）与吸附物的结合和4）催化剂活性/选择性。 这些工作将通过精确的催化剂合成、先进的表征技术（现场/操作中X射线光谱法、微量热法）和详细的动力学测量来完成。 该项目将确定基于Pd金属单原子设计催化剂的可能性和局限性。这项研究的跨学科性质，以及研究和教育计划的整合将导致一批学生获得关于多相催化和先进的实验室和同步加速器为基础的表征技术的独特教育经验。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Catalysts are used widely in industrial processes to improve energy efficiency and direct chemical reactions toward desired products. The project examines novel catalyst designs for an important class of industrial reactions – selective hydrogenations - used for many applications such as the production of plastics, fragrances and pharmaceuticals. The precious metal palladium (Pd) is widely used for selective hydrogenation reactions. The project aims to maximize utilization of the precious metal in the form of isolated atoms, and tailor their properties by anchoring them to covalent organic frameworks (COFs), which are highly crystalline porous materials with specific binding sites for the metal atoms. The investigators will synthesize and characterize the catalysts using a suite of laboratory- and synchrotron-based characterization techniques. The catalysts will be tested for the selective hydrogenation of acetylene to ethylene to determine how the binding sites affect the activity and selectivity of the Pd atoms. Beyond the research, the project involves education of graduate and undergraduate students with cross-training of researchers between the two institutions and focused efforts to increase participation of underrepresented groups in catalysis science.The project aims to tailor the properties of Pd single atoms using covalent organic frameworks (COF) as the support/ligand, and thus circumvent trade-offs between activity and selectivity associated with traditional metal oxide supported nanoparticle catalysts for the semi-hydrogenation of ethylene. Areas of focus include 1) the effects of the COF binding sites and secondary ligands on the Pd electronic properties, 2) hydrogen activation, 3) binding with adsorbates and 4) catalyst activity/selectivity. Those thrusts will be accomplished through precise catalyst synthesis, advanced characterization techniques (in-situ/operando X-ray spectroscopies, microcalorimetry) and detailed kinetic measurements. The project will identify the possibilities and limitations for designing catalysts based on Pd metal single atoms. The interdisciplinary nature of this research, and the integration of research and education plans will lead to a cadre of students obtaining a unique educational experience on heterogeneous catalysis and advanced lab- and synchrotron-based characterization techniques.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.