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

催化剂在工业过程中被广泛使用，以提高能源效率并直接进行化学反应以获得所需的产品。该项目考察了一类重要的工业反应--选择性加氢--的新型催化剂设计，该反应用于塑料、香水和药品的生产等许多应用。贵金属钯(Pd)被广泛用于选择性加氢反应。该项目旨在最大限度地利用孤立原子形式的贵金属，并通过将它们锚定在共价有机骨架(COF)上来调整它们的性质，COF是一种高度结晶的多孔材料，具有特定的金属原子结合位置。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来合成和表征催化剂。将对这些催化剂进行乙炔选择加氢合成乙烯的测试，以确定结合位置如何影响钯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，两个机构之间的研究人员交叉培训，并集中努力增加未被充分代表的基团在催化科学中的参与。该项目旨在利用共价有机骨架(COF)作为载体/配体来定制Pd单原子的性质，从而避免传统的金属氧化物负载纳米粒子催化剂在乙烯半加氢反应中的活性和选择性之间的权衡。研究的重点包括1)COF结合部位和二次配体对Pd电子性质的影响，2)氢活化，3)与吸附物的结合，4)催化剂的活性/选择性。这些推力将通过精确的催化剂合成、先进的表征技术(原位/操作手X射线光谱分析、微量热分析)和详细的动力学测量来实现。该项目将确定设计基于Pd金属单原子的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，将使一批学生获得关于多相催化和先进的基于实验室和同步加速器的表征技术的独特教育经验。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.