RUI: Evaluation of Ligand Effects in Molybdenum Catalyzed Deoxydehydration Reaction

在化学系化学催化项目的资助下，加州州立理工大学波莫纳分校（calpoly Pomona）的亚历克斯·约翰博士正在研究金属催化剂的使用，这种催化剂能够从有机基质上去除两个相邻的OH（即羟基）基团，并用碳-碳双键取代它们。碳碳双键是有用的，因为它们可以转化为各种其他有机官能团。目前能够进行这种转化的催化剂是基于昂贵的金属，不适合大规模的工业过程，而约翰博士正在开发的催化剂是基于钼的，相对便宜。通过实验和计算方法的结合，John博士正在对影响催化活性的因素进行全面的了解，从而为这种转化开发出更好的催化剂。这项工作的最终目标是将纤维素生物质衍生材料转化为可以用作化学原料的分子，以减少我们对化石资源的依赖。纤维素生物质衍生材料具有丰富的羟基，包括相邻的羟基。这项研究主要由约翰博士实验室的本科生进行，包括STEM领域代表性不足的少数民族。参与这项研究的学生对困扰全球化学工业的问题有了更好的了解，并为他们进入劳动力市场做好了更好的准备。生物质作为一种可持续的化学原料的潜在利用面临的一个关键挑战是其高度功能化的性质，因此需要有效和选择性地使这种可持续资源去功能化的方法。脱氧脱水反应在这方面是理想的，因为它将乙二醇转化为烯烃，这是平台化学物质。John博士正在探索模块化配体支持的明确定义的氧钼配合物在脱氧脱水（DODH）反应中的应用。氧钼配合物利用一系列已知与氧钼核心表现出差异配位的配体被合成并在该反应中测试以优化催化活性。通过评估DODH活性作为配体结构（立体/电子/柔韧性）的函数，进一步探索可行的氧钼配合物。通过结合实验（动力学研究）和计算（密度泛函理论，DFT）研究来了解配体对反应性影响的起源，从而获得机理见解。从这项研究中获得的数据和机制见解对更广泛的无机，有机金属和催化社区具有普遍的兴趣。该提案对具有不同背景/技能水平的学生，特别是本科生和少数民族学生具有包容性。从事这项研究的学生正在发展各种合成，表征和分析技术的技术技能，并为进入STEM领域的未来劳动力做好更好的准备。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。

With funding from the Chemical Catalysis Program in the Division of Chemistry, Dr. Alex John of the California State Polytechnic University Pomona (Cal Poly Pomona) is studying the use of metal catalysts that are capable of removing two adjacent OH (i.e., hydroxyl) groups from an organic substrate, and replacing them with a carbon-carbon double bond. Carbon-carbon double bonds are useful as they can be converted to a variety of other organic functional groups. Current catalysts capable of performing this transformation are based on expensive metals and are not suitable for large-scale industrial processes, while the catalysts that Dr. John is developing are based on molybdenum and are relatively inexpensive. Using a combination of experimental and computational methods, Dr. John is developing a comprehensive understanding of factors that affect catalytic activity and thereby developing superior catalysts for this transformation. The ultimate goal of this work is to convert cellulosic biomass-derived materials, which have an abundance of hydroxyl groups, including adjacent hydroxyl groups, into molecules that can be used as chemical feedstocks in order to reduce our dependence on fossil resources. This research is primarily being carried out by undergraduate students in Dr. John's laboratory, including underrepresented minorities in STEM areas. Students involved in this research gain a better understanding of the issues plaguing the global chemical industry, and they are better prepared as they enter the workforce.A key challenge plaguing the potential utilization of biomass as a sustainable chemical feedstock is its highly functionalized nature, and hence methods for efficient and selective defunctionalization of this sustainable resource are needed. The deoxydehydration reaction is ideal in this regard, as it converts glycols into olefins that are platform chemicals. Dr. John is exploring the utility of well-defined oxo-molybdenum complexes supported over modular ligands in the deoxydehydration (DODH) reaction. Oxomolybdenum complexes utilizing an array of ligands that are known to exhibit differential coordination to the oxo-molybdenum core are being synthesized and tested in this reaction to optimize catalytic activity. Viable oxo-molybdenum complexes are probed further by evaluating DODH activity as a function of ligand structure (sterics/electronics/flexibility). Mechanistic insights are gained by a combination of experimental (kinetic studies) and computational (Density Functional Theory, DFT) investigations to understand the origin of ligand effects on reactivity. Data generated and mechanistic insights gained from this study are of general interest to the broader inorganic, organometallic, and catalytic communities. The proposal is inclusive for students, especially undergraduates and minority students, with diverse backgrounds/skill levels. Students engaged in this research are developing technical skills in a variety of synthetic, characterization, and analytical techniques, and are better prepared to enter the future workforce in STEM areas.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.