CAREER: Promoting Selective Electrochemical CO2 Reduction by Controlling a Catalyst's Primary, Secondary, and Outer Coordination Spheres

将二氧化碳(CO2)转化为增值产品，作为一种将太阳能和风能等间歇性能源作为化学燃料进行储存的手段，具有至关重要的意义。二氧化碳转化的挑战之一是，该反应最活跃的催化剂往往会同时产生许多不同的产物，如一氧化碳、甲醇、甲烷、乙烯和副产物氢气(H2)。虽然将二氧化碳还原为这些化学品中的任何一种都是可取的，但由于产品分离和分离方面的问题，非选择性地产生多种产品是不理想的。以天然酶为灵感，McCrory博士正在创建合成系统，在该系统中，催化剂嵌入聚合物中，控制活性部位环境和反应物输送，以促进选择性地将二氧化碳还原为单一产品。拟议的研究具有重大的更广泛的社会影响，因为它为开发用于二氧化碳回收和能量储存的新催化剂系统提供了一个框架。与此同时，麦克罗里博士致力于通过一项分三步走的教育计划提高密歇根州的能源素养，包括1)科学交流方面的研究生培训，2)通过公共活动中的互动演示进行社区推广，以及3)在密歇根大学自然历史博物馆开发和实施一个以可再生能源储存为重点的展览。通过这种方法，麦克罗里博士正在努力让更广泛的社区更好地参与能源政策和使用决策。在化学部化学催化计划的资助下，密歇根大学安娜堡分校的查尔斯·C·L·麦克罗里博士正在通过控制催化剂活性中心周围的初级、次级和外部配位球来合成用于选择性二氧化碳还原的新的电催化材料。这一建议的中心假设是，分子电催化剂对二氧化碳还原等多电子转化的反应活性和选择性不仅可以通过改变金属中心周围的配体骨架来调节，还可以通过改变催化剂S的化学环境来控制H+和底物向金属活性中心的输送。为了验证这一假设，麦克罗里博士将带有大环配体的平面过渡金属络合物包裹在配位聚合物中。用多种光谱和电分析技术研究了聚合物-催化剂体系的配位环境、电子结构和催化活性。通过系统地修改配体、聚合物和反应条件，McCrory博士独立地控制围绕金属中心的初级、次级和外部配位球，并确定每个配位球对整体催化活性和产品选择性的影响。从这项研究中获得的知识对于开发选择性减少二氧化碳的新催化剂-聚合物复合系统至关重要，并对设计用于可再生能源储存和二氧化碳减排的新电催化系统具有重大的更广泛的社会影响。此外，麦克罗里博士正在努力提高密歇根州的能源素养，方法是为普通公众设计与可再生能源储存相关的互动演示，并在密歇根大学自然历史博物馆开发一个展览，突出可再生能源储存方面的进展和挑战。综上所述，该提案的研究和综合教育部分突出了一种克服能源储存和二氧化碳转化方面的挑战的新方法，并将影响这些重要问题在科学和社会层面上的解决方式。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。

The conversion of carbon dioxide (CO2) into value-added products is of fundamental importance as a means of storing intermittent energy sources like solar and wind as chemical fuels. One of the challenges in CO2 conversion is that the most active catalysts for this reaction tend to simultaneously produce a number of different products such as carbon monoxide, methanol, methane, ethylene, and the side product hydrogen gas (H2). While the reduction of CO2 to any one of these chemicals is desired, the non-selective generation of multiple products is non-ideal due to problems in product separation and isolation. Using natural enzymes as inspiration, Dr. McCrory is creating synthetic systems in which catalysts are embedded within polymers that control the active site environment and reactant delivery to facilitate selective CO2 reduction to single products. The proposed research has significant broader societal impact in that it provides a framework for the development of new catalyst systems for CO2 recycling and energy storage. Concurrently, Dr. McCrory is focused on increasing energy literacy in Michigan using a 3-step education plan involving 1) graduate student training in scientific communication, 2) community outreach through interactive demonstrations at public events, and 3) the development and implementation of an exhibit at the University of Michigan Natural History Museum focused on renewable energy storage. Through this approach, Dr. McCrory is working to enable the broader community to better engage in energy policy and usage decisions. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Charles C. L. McCrory of the University of Michigan, Ann Arbor is synthesizing new electrocatalytic materials for selective carbon dioxide reduction by controlling the primary, secondary, and outer coordination spheres surrounding the catalyst's active site. The central hypothesis for this proposal is that the reactivity and selectivity of molecular electrocatalysts for multi-electron transformations such as CO2 reduction can be modulated not only by modifying the ligand framework surrounding the metal center, but also by modifying the catalyst?s chemical environment to control H+ and substrate delivery to the metal active site. To test this hypothesis, Dr. McCrory is encapsulating planar transition metal complexes with macrocyclic ligands inside of coordinating polymers. The coordination environment, electronic structure and catalytic activity of the resulting polymer-catalyst systems are studied using a variety of spectroscopic and electroanalytical techniques. Through systematic modifications of the ligand, polymer, and reaction conditions, Dr. McCrory is independently controlling the primary, secondary, and outer coordination spheres surrounding the metal center and determining the effect of each coordination sphere on the overall catalytic activity and product selectivity. The knowledge gained from this study is crucial for the development of new catalyst-polymer composite systems for selective CO2 reduction and has significant broader societal impact in the design of new electrocatalytic systems for renewable energy storage and CO2 mitigation. In addition, Dr. McCrory is working to increase energy literacy in Michigan through the design of interactive demonstrations relevant to renewable energy storage for the general public and the development of an exhibit at the University of Michigan Natural History Museum highlighting progress and challenges in renewable energy storage. Together, the research and integrated education components of this proposal highlight a new approach to overcoming challenges in energy storage and carbon dioxide conversion and will impact the way these important issues are addressed, both at the scientific and societal level.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.