Ligand-centered copper, zinc, and metal-free hydrogen evolution catalysts

化学学部的化学催化项目支持Craig A. Grapperhaus和Pawel M. Kozlowski教授的项目。Grapperhaus教授和Kozlowski教授是路易斯维尔大学化学系的教员。他们正在开发用于氢的演化和氧化的新型配体中心电催化剂。氢是一种很有前途的替代无碳燃料，是工业和农业过程的重要组成部分。目前，95%的工业氢气来自不可持续的化石燃料裂解。本项目中的催化剂采用配体中心方法。配体是一种能将中心金属结合成络合物的小分子。以配体为中心的方法的一个主要优点是有机框架作为活性位点，允许开发无金属或由可持续过渡金属（例如铜）或非过渡金属（例如锌）促进的催化剂。该项目促进了可持续的析氢/氧化系统的开发，这些系统具有实际应用价值。它进一步加强了研究人员与康涅狄格州可再生能源中心之间的联系，该中心促进了肯塔基州高校、私营企业和致力于可再生能源解决方案的非营利组织之间的合作关系。研究生和本科生学习不同的技能组合，包括合成、表征、电化学和计算。该项目非常适合本科研究生，他们参与并对许多年轻的在职科学家感兴趣和关注的主题做出贡献。这个项目中的催化剂是一种新兴的以配体为中心的方法的前沿，它避免了传统的金属氢化物，这已经得到了很好的研究。相比之下，以配体为中心的方法仍然不发达，关于结构-活性关系的基本问题仍有待回答。在三种金属负载条件下制备了对称和不对称N2S2双硫代氨基脲催化剂：1)过渡金属（铜）；2)非过渡金属（锌）；3)不含金属的。通过改变配体和金属组分上的官能团来评价配体和金属对催化活性的影响。以配体为中心的氢析出/氧化所需的必要特征正在通过系统地“修剪”双硫代氨基脲框架来建立，包括基于较大配体片段的新催化剂的合成。利用在项目中获得的见解，第三代以配体为中心的催化剂被设计为“活性位点口袋”，将关键成分定位在适当的几何位置，以促进活性。该教育计划包括研究生和本科生培训，重点是少数民族和第一代大学生。

The Chemical Catalysis Program of the Chemistry Division supports the project by Professors Craig A. Grapperhaus and Pawel M. Kozlowski. Professors Grapperhaus and Kozlowski are faculty members of the Department of Chemistry at the University of Louisville. They are developing novel ligand-centered electrocatalysts for the evolution and oxidation of hydrogen. Hydrogen serves as a promising alternative carbon-free fuel and is an essential building block for industrial and agricultural processes. Currently, 95% of industrial hydrogen derives from unsustainable fossil-fuel cracking. The catalysts in this project employ a ligand-centered approach. Ligands are small molecules that bind a central metal into a complex. A major advantage of the ligand-centered approach is that the organic framework functions as the active site, allowing the development of catalysts that are metal-free or promoted by sustainable transition-metals (e.g. copper) or non-transition metals (e.g. zinc). The project facilitates the development of sustainable hydrogen evolution/oxidation systems, which have practical applications. It further strengthens connections between the researchers and the Conn Renewable Energy Center, a center that promotes partnerships among Kentucky's colleges and universities, private industries, and non-profit organizations dedicated to renewable energy solutions. Graduate students and undergraduate participants learn a diverse combination of skills including synthesis, characterization, electrochemistry, and computation. The project is well suited for undergraduate research students, who participate and make contributions on a topic of interest and concern to many young scientists-in-training.The catalysts in this project are at the forefront of an emerging ligand-centered approach that avoids traditional metal-hydrides, which have been well studied. In contrast, the ligand-centered approach remains underdeveloped, and fundamental questions regarding structure-activity relationships remain to be answered. Symmetric and asymmetric N2S2 bis-thiosemicarbazone catalysts are prepared under three metal loading conditions: 1) transition metal (copper); 2) non-transition metal (zinc); 3) metal-free. The functional groups on the ligands and metal-component are varied to evaluate ligand- and metal effects on catalytic activity. The requisite features required for ligand-centered hydrogen evolution/oxidation are being established through a systematic "trimming" of the bis-thiosemicarbazone framework involving the synthesis of new catalysts based on fragments of the larger ligand. Using insights developed during the project, a third-generation of ligand-centered catalysts are under design as "active site pockets" that position key components in the proper geometric positions to promote activity. The educational plan includes graduate and undergraduate training with an emphasis on minority and first-generation college students.