Understanding the Mechanism of C-X hydrogenolysis Catalyzed by Supported Metal Nanoparticles

在化学系化学催化项目的资助下，巴纳德学院的奥斯汀教授、缅因州大学的弗雷德里克和施瓦茨教授以及休斯顿大学的格雷博教授将研究如何催化减少碳-卤键。这项工作与环境的化学有关。特别是，许多现代杀虫剂含有这样的碳-卤键(碘、溴、氯或氟)。这些分子的设计部分是因为它们是稳定的，但这种稳定性也可能在预计的产品生命周期结束时成为一种负担。这个合作团队将使用一系列方法来学习如何选择性地还原去除这些分子中的卤素。该团队还将研究能够打破这些键的催化剂，以准确地了解它们如何进行这一重要的化学作用，并建立计算模型来设计更具实用性的新催化剂。团队的所有成员都致力于使科学工作者多样化。PIs将致力于招募女性进入科学界，特别是通过巴纳德学院新成立的4+1项目，该项目为项目参与者提供机会，在完成巴纳德学院的专业本科学位后，仅在一年内就完成哥伦比亚大学的化学工程硕士学位。被选中的学生将在缅因州大学的化学工程实验室和休斯顿大学的计算化学工程实验室，以及在巴纳德学院和哥伦比亚大学的材料表征实验室工作，以便他们将学习这一多学科努力的所有方面。这个研究项目将测试几个关于负载金属纳米颗粒催化芳香族C-X键氢解性质的机械假说。芳香族化合物中C-X键氢解的反应速率数据显示，对X的同一性缺乏敏感性，这意味着C-X键的断裂不是速率决定的。该团队假设，表面化学在卤代芳香族化合物的脱卤化过程中起着关键作用，其方式与类似的烷基-X物种的化学非常不同。合作团队将研究在日益复杂的系统上C-X键氢解的详细步骤，并使用来自这些研究的数据来为密度泛函理论(DFT)计算提供信息，并允许联合实验/计算团队建立微观动力学模型。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。

With funding from the Chemical Catalysis Program of the Chemistry Division, Professors Austin of Barnard College, Frederick and Schwartz of University of Maine, and Grabow of University Houston will study how to catalytically reduce off carbon-halogen bonds. The work is of relevance to the chemistry of the environment. In particular, a number of modern pesticides contain such carbon-halogen (iodine, bromine, chlorine, or fluorine) bonds. These molecules have been designed in part because they are stable, but that stability can also becomes a liability at the end of the projected product life cycle. This collaborative team will use a range of approaches to learn how to selectively reductively remove the halogens from these molecules. The team will also study catalysts that can break these bonds to understand precisely how they carry out this important chemistry, and build computational models to design new catalysts of greater practicality. All of the members of the team are committed to diversifying the scientific workforce. The PIs will work to recruit women into science, and into this research team in particular, through a newly formed 4 + 1 program at Barnard College, that provides program participants with the opportunity to complete a master's degree in chemical engineering at Columbia University in just one year after completing their specialized undergraduate degree at Barnard College. The selected students will spend time in a chemical engineering lab at the University of Maine and a computational chemical engineering lab at the University of Houston, in addition to time working at Barnard College and in the materials characterization labs at Columbia University, so that they will learn all of the facets of this multidisciplinary effort.This research project will test several mechanistic hypotheses about the nature of aromatic C-X bond hydrogenolysis catalyzed by supported metal nanoparticles. Reaction rate data for C-X bond hydrogenolysis in aromatic compounds shows a surprising lack of sensitivity to the identity of X, implying that C-X bond breaking is not rate-determining. The team hypothesizes that surface chemistry plays a critical role in dehalogenation of halogenated aromatic compounds in ways that are very different from the chemistry for the analogous alkyl-X species. The collaborative team will study the detailed steps of C-X bond hydrogenolysis on systems of increasing complexity and use data from those studies to inform density functional theory (DFT) calculations and allow for the joint experimental/computational team to build micro-kinetic models.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.