CAS: Rational Design of Chiral Frustrated Lewis Pair Frameworks for Metal-free Heterogenous Asymmetric Hydrogenation

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Shengqian Ma of the University of North Texas is studying a new type of metal-free porous solid catalyst to accomplish challenging chemical transformations historically limited to rare and expensive metals. This new catalyst class may overcome deficiencies of both existing catalysts, providing a robust framework to facilitate precise tunability. By fine-tuning electron-poor (Lewis acid) and electron-rich (Lewis base) moieties, as well as the microscopic environment surrounding them, the so-called frustrated Lewis pairs embedded in an easily tailorable framework will allow non-metals to achieve metal-like reactivity. Moreover, as a metal-free material, this new class of catalyst will be well-positioned for use in pharmaceutical and food industries, inherently circumventing rigorous purification otherwise necessary to remove potentially toxic metals. This project will support research efforts of a broad team, with researchers spanning high-school, undergraduate, and graduate levels. Students will be trained to utilize an exhaustive set of cutting-edge instrumentation for synthesis, characterization, analysis, and modelling, setting the foundation for impactful careers in critical STEM disciplines. With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Shengqian Ma of the University of North Texas is studying a new class of metal-free heterogeneous catalysts for asymmetric hydrogenation reactivity based on frustrated Lewis pairs (FLPs) confined within the nanospace of covalent organic frameworks (COFs). The project will build upon Professor Ma’s recent advances in the field, systematically quantifying primary, secondary, and tertiary sphere chiral induction effects towards achieving high enantioselectivity for traditionally promiscuous substrates such as the asymmetric hydrogenation of tetrasubstituted enamides – a key challenge in the synthesis of emerging pharmaceuticals. Strategies will be developed to rationally tailor COF-supported FLP microenvironments followed by systematic evaluation of the resulting enantioselective and chemoselective hydrogenation of an established set of substrates. Additionally, in situ spectroscopy supported by computational modelling will elucidate outstanding questions in FLP-based hydrogenation catalysis, leveraging methods pioneered in Professor Ma’s group. Insights garnered from this project will be directly applicable to other framework-based systems for asymmetric catalysis and beyond. This project will involve researchers spanning high-school, undergraduate, and graduate levels, setting the foundation for their impactful careers in critical STEM disciplines. 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.