Rational design of photocatalysts

光氧化还原催化由于其潜在的执行其他困难的化学转化，以及它的能力，可以利用可见光或近紫外光，可以有效地产生LED而获得了许多兴趣。虽然它已经在一系列应用中得到了证明，但光催化剂设计没有明确的概念，应用中使用的确切催化剂似乎是通过反复试验而不是由理解和合理的设计标准来指导的。该项目旨在将建模和实验工作结合起来，根据以下标准(其中包括)来设计和优化光催化剂的性能：-光吸收：可用于将基片的电子提升到激发轨道的能量将取决于从光催化剂转移到基片的能量，从而最终取决于光催化剂所吸收的能量。-吸附性能(多相催化剂)：将底物吸附到多相光催化剂上是将能量从催化剂转移到底物的先决条件。假设底物准备好与第二种试剂进行反应，第二种试剂在催化剂表面的吸附性能将影响反应路径和所需的催化剂表面。最后，产物(或试剂)从表面上的脱附将影响催化系统的性能，因为它将释放表面，以便下一组试剂分子转化为产物配位性质(异相催化剂)：底物与具有光催化活性的配位金属的配位将决定反应是否被催化以及催化循环是什么样子。-催化系统的电子特性：典型的氧化还原光催化系统包括一个用于还原反应的催化剂和另一个用于氧化反应的催化剂。这就要求电子可以从氧化催化剂移动到相应的位置，在那里进行相应的还原(并避免电子-空穴复合)。找出一对合适的催化剂，并以适当的方式将它们结合在一起，这样电子就可以根据需要移动，这将对光氧化还原催化系统的性能至关重要。(请注意，关闭催化循环还需要分子/离子/部分的传质。)这一博士课程将通过对上述(和其他重要的)参数建模，通过实验测试、验证和改进模型，来研究氧化还原-光催化系统的一到三个样本的关键方面。这将包括分析与产品和副产品有关的产品流，并开发基本反应网络的概念。一个目标将包括识别光催化系统中限制速度/性能的步骤或特征，并提出改进有效性和效率的措施(产率和选择性、周转次数等)。为了更好地利用该系统，并建议适当的催化剂组合和配方，该方案将致力于通过侧重于一种光催化系统，与REPACT中的另外两名学生发挥协同作用。其中一名学生正在研究氧化性光催化剂的合成和分析(Melanie Nutter)，另一名学生(Janusz Siwek)正在研究反应器设计和放大。

Photo-redox catalysis has gained a lot of interest due to its potential of performing otherwise difficult chemical conversions and its ability to use visible or near UV light, that can be efficiently generated with LEDs. While it has been demonstrated in a range of applications, there is no clear concept for photocatalyst design and the exact catalyst used in an application appears to be by trial and error rather than guided by understanding and rational design criteria. This project aims at combining modelling and experimental work to design and optimize photocatalyst performance based on the following criteria (among others): - Light absorption: the energy available for lifting electrons of a substrate into an excited orbital will depend on the energy transferred from the photocatalyst to the substrate and therefore ultimately on the energy absorbed by the photocatalyst. - Sorption properties (heterogeneous catalysts): The adsorption of a substrate to a heterogeneous photocatalyst is a prerequisite to the energy transfer from the catalyst to the substrate. Assuming that the substrate is then ready to perform the reaction with a second reagent, the sorption properties of the latter to the catalyst surface will affect the reaction pathway and the required catalyst surface. And finally the desorption of the product (or the reagents) from the surface will affect the performance of the catalytic system, as it will free up the surface for the next set of reagent molecules to be converted into product- Coordination properties (heterogeneous catalysts): The coordination of substrates to photocatalytically active coordination metals will determine, whether a reaction is catalyzed and how the catalytic cycle looks like. - Electronic properties of the catalytic system: a typical redox photocatalytic system includes one catalyst for the reduction and another one for the oxidation reaction. This entails that electrons can move from the oxidizing catalyst to the site, where the corresponding reduction is to be performed (and to avoid electron-hole recombination). Identifying an appropriate pair of catalysts and combining them in an appropriate way, so the electrons can move as required will be crucial for the performance of the photo-redox-catalytic system. (Note that also mass transport of molecules/ions/moieties will be required to close the catalytic cycle.) This Ph.D. programme will be looking at the critical aspects of one to three exemplars for redox-photocatalytic systems - By modelling the above (and significant other) parameters - By experimentally testing, verifying, refining the models. This will include analyzing the product stream with respect to products and side products and develop concepts for the underlying reaction network.One goal will include the identification of the rate-/performance-limiting steps or features in a photocatalytic system and suggest measures to improve the effectiveness and efficiency (yield and selectivity, turn-over number, etc.) of the system and suggest appropriate catalyst combinations and formulations,The programme will aim at leveraging synergies with two other students within React by focusing on one photocatalytic system. One of the students is working on the synthesis and analysis of an oxidizing photocatalyst (Melanie Nutter), the other one (Janusz Siwek) on reactor design and scale up.