SusChEM: Rigid and Flexible Linker Systems for Superior Immobilized Catalysts

美国国家科学基金会化学催化项目支持德克萨斯农工大学Janet Bluemel教授对均相和固定化镍分子催化剂的研究，以阐明金属络合物分解形成纳米颗粒的过程。镍(0)催化剂通过磷化氢连接剂固定在表面上，这些连接剂从广泛的单、二、三叉戟配体中选择，包括灵活的烷基链或刚性的四苯基元素核心。配体的战略性选择有助于区分表面二聚化和团聚，这是最终纳米颗粒形成的关键步骤。以苯乙炔的环三聚化反应为模型反应，研究了固定化催化剂的选择性和活性，并监测了潜在的纳米颗粒形成。利用31P T1弛豫时间和HRMAS NMR数据量化了金属配合物在表面上从一个不协调的磷化氢连接体迁移到下一个的动力学。还研究了Ni(0)以外的金属配合物和不同的催化反应，以探索模型催化体系所获得的见解的一般适用性。固定化催化剂具有改善工业规模化学过程的潜力，因此，该项目可以通过提供具有优越活性，选择性和寿命的非贵金属催化剂的制备和使用的一般方法来改善大规模化学合成的环境可持续性。参与该项目的研究生和本科生接受跨学科培训，并获得非晶材料表征的先进技术经验。化学催化项目支持德克萨斯农工大学Janet Bluemel教授比较均相催化剂和固定化催化剂的差异。在均相催化过程中，金属催化剂可以形成纳米颗粒，导致非均相催化剂在溶液中悬浮。从固定化催化剂开始，同样的过程导致纳米颗粒在表面形成。这种不可控的情况是不可取的，因为它是不可预测的，通常是不可预防的，并且可能改变催化剂的选择性或缩短其寿命，降低催化剂的可回收性。本研究项目研究均相和固定化分子镍催化剂，以阐明金属催化剂分解（如在表面分解或在溶液中团聚）形成纳米颗粒的相关过程。该项目通过提供具有优越活性、选择性和寿命的非贵金属催化剂的制备和使用的一般方法，有可能改善大规模化学合成的环境可持续性。参与该项目的研究生和本科生接受跨学科培训，进行国际合作，并获得先进分析技术的经验。

The NSF Chemical Catalysis Program supports the efforts of Professor Janet Bluemel of Texas A&M University to investigate homogeneous and immobilized molecular nickel catalysts in order to clarify the processes by which metal complexes decompose to form nanoparticles. Nickel(0) catalysts are immobilized on surfaces via phosphine linkers chosen from a broad range of mono-, di-, and tridentate ligands that incorporate flexible alkyl chains or rigid tetraphenylelement cores. Strategic ligand selection helps discriminate between dimerization on the surface and agglomeration as the crucial step in the eventual nanoparticle formation. The cyclotrimerization of phenylacetylene is used as a model reaction to study the selectivity and activity of the immobilized catalysts and to monitor potential nanoparticle formation. The dynamics of metal complex migration from one uncoordinated phosphine linker to the next on the surface is quantified using 31P T1 relaxation times and HRMAS NMR data. Metal complexes other than Ni(0) and different catalytic reactions are also investigated to probe the general applicability of the insights gained with the model catalytic system. Immobilized catalysts have the potential to improve industrial scale chemical processes and thus, this project may improve the environmental sustainability of large scale chemical synthesis by providing general methodologies for the preparation and use of non-precious metal catalysts with superior activities, selectivities, and lifetimes. Graduate and undergraduate students involved in the project receive interdisciplinary training and gain experience in advanced techniques for the characterization of amorphous materials.The Chemical Catalysis Program supports the efforts of Professor Janet Bluemel of the Texas A&M University to compare differences in homogeneous and immobilized catalysts. During homogeneous catalysis, nanoparticles can form from the metal catalyst resulting in a suspension of heterogeneous catalysts in solution. Starting from immobilized catalysts, the same process leads to nanoparticle formation on the surface. This uncontrollable scenario is undesirable because it is not predictable, not generally preventable, and may change the selectivity of the catalyst or shorten its lifetime, diminishing the recyclability of the catalyst. This research project investigates homogeneous and immobilized molecular nickel catalysts in order to clarify the processes associated with metal catalyst decomposition (e.g. decomposition on the surface or agglomeration in solution) to form nanoparticles. This project has the potential to improve the environmental sustainability of large scale chemical synthesis by providing general methodologies for the preparation and use of non-precious metal catalysts with superior activities, selectivities, and lifetimes. Graduate and undergraduate students involved in the project receive interdisciplinary training, collaborate internationally, and gain experience in advanced analytical techniques.