Earth abundant element catalysts - Fe, B, Al not feeble compounds for polymer production and conversion of carbon dioxide

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Discovery of new catalysts is key to the production of energy, chemicals and materials in an environmentally-friendly way. Our research program focuses on using earth-abundant elements at the centre of our catalysts by targeting aluminum, iron and boron. We will use our catalysts to build new molecules from carbon dioxide, and to prepare renewable and degradable polymers. Studying earth-abundant elements in catalysis is challenging but allows chemists to access mechanistically distinct reactions compared with precious metals, and so some of our discoveries will be unforeseen. We recently discovered a metal-free process for converting carbon dioxide to either cyclic carbonate or polycarbonate products upon reaction with suitable epoxides. This works at atmospheric pressure and turnover frequencies in excess of 1200 per hour have been observed. Preliminary results show that we can exploit the inherent reactivity of boranes to yield functional polymers in a one-pot, sequential tandem catalytic process, and we will explore these reactions further during the next 5 years. We will also develop new homogeneous catalysts based on aluminum and iron coordination compounds. The iron compounds themselves will show oxidation state dependent reactivity, and introduction of ferrocene (an iron molecule) into aluminum and boron compounds will lead to redox-switchable catalyst systems where different catalytic behaviours can be turned on and off. The switching may also affect physical properties such as solubility and adsorption on surfaces, which could be used to easily separate homogeneous catalysts from products. Incorporation of such catalyst behaviours could decrease the time required for commercial processes that use carbon dioxide. In our work using new catalysts for the reactions of carbon dioxide with epoxides and aziridines, including those derived from biological feedstocks (e.g. terpenes, amino acids), we will develop a fundamental understanding of our catalyst systems through in situ IR spectroscopic reaction monitoring, UV-Vis titrations (in the case of iron), and multinuclear NMR studies (including boron and aluminum). The nitrogen-analogs of epoxides, aziridines, have been studied to a much lesser extent by researchers worldwide, and can potentially be prepared from renewable amino alcohols. We anticipate that our boron and aluminum catalyst systems will be more active in the reactions of aziridines and carbon dioxide compared with more commonly studied transition metal catalysts. Furthermore, expanding the scope of co-reagents in these reactions so aziridines are more widely employed or polymer modification can be achieved in a tandem process is critically important. In addition to fundamental scientific discoveries, this research program will attract and train the next generation of green chemistry researchers who will make a considerable impact in Canadian science, technology and education.