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

新催化剂的发现是以环境友好的方式生产能源、化学品和材料的关键。我们的研究计划重点是通过瞄准铝、铁和硼，在我们的催化剂中心使用富含稀土的元素。我们将使用我们的催化剂从二氧化碳中构建新的分子，并制备可再生和可降解的聚合物。研究催化中富含稀土的元素是具有挑战性的，但与贵金属相比，化学家可以获得机械上不同的反应，因此我们的一些发现将是不可预见的。我们最近发现了一种无金属的方法，通过与合适的环氧化物反应，将二氧化碳转化为环状碳酸酯或聚碳酸酯产物。这是在大气压下工作的，已经观测到每小时超过1200次的周转频率。初步结果表明，我们可以利用硼烷固有的反应性，在一锅连续串联催化过程中生产功能聚合物，我们将在未来5年进一步探索这些反应。我们还将开发基于铝和铁配位化合物的新型均相催化剂。铁化合物本身将表现出氧化态相关的反应活性，而将二茂铁(一种铁分子)引入铝和硼化合物中将导致氧化还原可切换催化剂系统，其中不同的催化行为可以被打开和关闭。这种转换还可能影响表面的溶解度和吸附等物理性质，这些性质可以很容易地将均相催化剂与产品分离。这种催化剂行为的加入可以减少使用二氧化碳的商业过程所需的时间。在我们将新型催化剂用于二氧化碳与环氧化物和氮杂环丙烷的反应中，包括那些从生物原料(如萜烯、氨基酸)中提取的催化剂，我们将通过原位红外光谱反应监测、UV-Vis滴定(对于铁)和多核核磁共振研究(包括硼和铝)来对我们的催化剂体系有一个基本的了解。环氧化物的含氮类似物，氮杂环丙烷，世界各地的研究人员研究的程度要小得多，而且有可能从可再生的氨基醇中制备。我们预计，与通常研究较多的过渡金属催化剂相比，我们的硼和铝催化剂体系在氮杂环丙烷和二氧化碳的反应中将更加活跃。此外，扩大这些反应中共试剂的范围，以便更广泛地使用氮杂环丙烷或能够在串联过程中实现聚合物改性，这一点至关重要。除了基础科学发现，这项研究计划还将吸引和培养下一代绿色化学研究人员，他们将对加拿大的科学、技术和教育产生相当大的影响。

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.