Atomically-Dispersed Co and Cu Catalysts for Reactions Involving C-H Activation

水力压裂技术极大地提高了天然气原料的可用性。国内天然气储量如此丰富，表明它可能成为取代石油生产大宗化学品的候选产品。使用生物质衍生的碳资源将是生产商品化学品的一种更环保的原料。然而，将天然气和生物质转化为商品化学品都需要催化升级反应，其中一个分子被选择性地转化为另一个更高价值的所需分子。为了使天然气和生物质在经济上与石油作为原料具有竞争力，这种催化转化必须具有高选择性（即避免不必要的副产品）和廉价性。然而，今天的大多数催化剂使用昂贵的贵金属，只有适度的选择性，并且往往需要能源密集型的高温高压条件。将替代化学原料转化为增值化学品的经济催化过程的发展将大大受益于从低成本的地球丰富元素中提取的新催化剂的发现和工程。最近的观察表明，一些原子分散的、富含土壤的金属在碳载体上的活性和选择性接近贵金属催化剂，而成本要低得多。该项目旨在确定载氮碳中分离的钴和铜原子的原子和电子结构，并将这些特征与代表性催化反应中的催化性能联系起来。这个项目将把原子分散的钴和铜离子在载氮碳中的催化性能与活性催化位点的配位环境和化学状态联系起来。后者将采用高分辨率电子显微镜、原位x射线吸收光谱和原位x射线光电子能谱进行探测。反应性将通过醇氧化脱氢和碳氢化合物脱氢来评估。本研究结果将提供活性位点的结构模型，并为设计和合成新的、高度分散的、丰度高的金属原子催化剂提供通用规则。该项目涉及本科生和研究生的研究、培训和教育。与德国马克斯普朗克研究所和两个美国国家实验室的合作是该项目的一部分。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Hydraulic fracturing technology has dramatically increased the availability of natural gas feedstocks. This abundance of readily available domestic natural gas suggests it may be a candidate to displace petroleum in the production of commodity chemicals. Use of biomass-derived carbon resources would be an even more environmentally benign feedstock to produce commodity chemicals. Yet, the conversion of both natural gas and biomass into commodity chemicals requires a catalytic upgrading reaction, in which one molecule is selectively converted to a second desired molecule of higher value. For natural gas and biomass to be economically competitive with petroleum as a feedstock, this catalytic conversion must be both highly selective (i.e. unwanted byproducts are avoided) and inexpensive. However, most of today's catalysts use expensive precious metals, have only modest selectivity, and often require energy-intensive high temperature and pressure conditions. Development of economic catalytic processes that convert alternative chemical feedstocks into value added chemicals would benefit greatly by the discovery and engineering of new catalysts that are derived from low-cost earth-abundant elements. Recent observations suggest some atomically-dispersed, earth abundant metals on a carbon support approach the activity and selectivity of a precious metal catalyst, at much less expense. This project seeks to identify the atomic and electronic structure of isolated cobalt and copper atoms in nitrogen-loaded carbon and relate those characteristics to catalytic performance in representative catalytic reactions.This project will correlate the catalytic performance of atomically-dispersed cobalt and copper ions in nitrogen-loaded carbon to the coordination environment and chemical state of the active catalytic site. The latter will be probed with high resolution electron microscopy, in-situ X-ray absorption spectroscopy and in-situ X-ray photoelectron spectroscopy. Reactivity will be assessed via alcohol oxidative dehydrogenation and hydrocarbon dehydrogenation. Results from this study should provide structural models of the active sites and lead to generalized rules for designing and synthesizing new, highly-dispersed, earth-abundant metal atom catalysts. The project involves research training and education of undergraduate and graduate students. Collaborations with the Max Planck Institutes in Germany and two US national laboratories are part of the project.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.