RUI: Evaluation of Ligand Effects in Molybdenum Catalyzed Deoxydehydration Reaction

在化学系化学催化计划的资助下，加州州立理工大学波莫纳分校(Cal Poly Pomona)的Alex John博士正在研究使用金属催化剂，这种催化剂能够从有机底物中移除两个相邻的羟基(即羟基)，并将它们替换为碳-碳双键。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流程，而约翰博士正在开发的催化剂是基于钼的，相对便宜。通过实验和计算相结合的方法，约翰博士正在全面了解影响催化活性的因素，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用作化学原料的分子，以减少对化石资源的依赖。纤维素生物质衍生材料含有丰富的羟基，包括邻近的羟基。这项研究主要是由约翰博士实验室的本科生进行的，包括STEM地区代表不足的少数族裔。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，当他们进入劳动力大军时，他们做好了更好的准备。生物质作为可持续化学原料潜在利用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。在这方面，脱氧脱水反应是理想的，因为它将乙二醇转化为作为平台化学品的烯烃。John博士正在探索在脱氧脱水(DODH)反应中以模块配体为载体的定义明确的氧钼络合物的用途。利用一系列已知与氧钼核具有不同配位的配体合成了氧钼配合物，并在该反应中进行了测试，以优化催化活性。通过评估DODH活性作为配体结构(空间/电子/柔性)的函数，进一步探索了可行的氧代钼配合物。通过实验(动力学研究)和计算(密度泛函理论，DFT)相结合的研究，获得了机理上的见解，以了解配体对反应活性的影响的起源。从这项研究中产生的数据和获得的机械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族裔学生具有包容性。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 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.