RUI: Evaluation of Ligand Effects in Molybdenum Catalyzed Deoxydehydration Reaction

Cal Poly Pomona Foundation, Inc., Pomona CA

Investigators

Abstract

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.