Computational Modeling of Carbon Monoxide Dehydrogenase Model Systems for Carbon Dioxide Fixation

项目摘要 大气中的二氧化碳浓度已经达到了迄今为止的最高水平，这是迫在眉睫和可怕的。 对环境和人类健康的所有领域造成的后果。基于这些迫在眉睫且日益严重的威胁， 迫切需要将我们目前的基础设施从化石燃料过渡到可再生能源。在……里面 在此背景下，太阳能或可再生电力可用于推动二氧化碳和水的催化转化 转化为富含能量的化学物质(类似于生物系统)，能量无限期地储存在化学键中 按需使用。二氧化碳的化学还原为其他化学能更高的碳化合物 将关闭碳循环，并提供与现有基础设施兼容的化学燃料。然而， 现有的二氧化碳催化剂往往存在过电位高、循环频率低、底物质量差等问题。 在H2O存在下的选择性。相比之下，一氧化碳脱氢酶(CODH)酶，如 嗜氢羧酸杆菌镍一氧化碳脱氢酶II能提取能量 以高速率和高选择性地将CO可逆转化为CO2 同时在热力学势能附近运行。Ni-CODHCh II的晶体结构揭示了一个 铁-硫团簇与镍原子结合，称为C-团簇。这个C星团的一个结构特征是 存在Fe3S4团簇，它将镍和铁原子连接在一起。这次合作的刘易斯酸碱 Pair被认为是第二个非常规活动的关键特征。这项提议的长期目标是 是利用计算化学与互补的实验努力相结合来设计 创新的催化剂，模仿选择性CODH酶的基本结构特征和功能 在H2O存在下，二氧化碳转化为一氧化碳。我们建议通过以下方式实现这一目标 具体目标：(I)研究大环氧化还原活性配体支持的地球丰富的物质；和(Ii) 通过使用次级分子中的带电官能团来催化一氧化碳的产生 协调球体。更具体地说，这项提案概述了合理设计创新催化剂的计划 用于根据热力学和动力学性质将二氧化碳转化为一氧化碳。这些原则一直是 在多相催化中被确定为关键。例如，在萨巴蒂尔原理中， 关键中间体中金属的底物结合能与总催化剂速率有关。对.的使用 分子催化剂将使我们能够调整这些关键的键能，以实现最佳值。在这 背景下，电子结构计算将提供一种直接的方法来研究关键的热力学 以及开发具有(I)高选择性的分子催化剂所需的动力学性质 需要的产品；和(Ii)长时间的快速动力学。这些目标的成功实现将产生 基于基本热力学和动力学性质的下一代设计通用指南 用于将二氧化碳还原为CO或任何高价值C1产品的分子催化剂。

Project Abstract Atmospheric CO2 concentrations have reached their highest to date, which holds immediate and dire consequences for the environment and all areas of human health. Based on these imminent and growing threats, there is an urgent need to transition our current infrastructure from fossil fuels to renewable energy sources. In this context, solar energy or renewable electricity could be used to drive the catalytic conversion of CO2 and H2O into energy-rich chemicals (similar to biological systems) whereby energy is stored indefinitely in chemical bonds for on-demand use. The chemical reduction of CO2 to other carbon compounds with higher chemical energy would close the carbon cycle and deliver chemical fuels that are compatible with existing infrastructure. However, existing CO2 catalysts often suffer from very high overpotentials, low turnover frequency and poor substrate selectivity in the presence of H2O. In contrast, carbon monoxide dehydrogenase (CODH) enzymes, such as the nickel-carbon monoxide dehydrogenase II from Carboxydothermus hydrogenoformans are able to extract energy from their environments in order to carry out the reversible conversion of CO to CO2 at high rates and selectivity while operating near the thermodynamic potential. Crystal structure of Ni-CODHCh II reveals the presence of an iron-sulfur cluster combined with a nickel atom, called C-cluster. One structural feature of this C-cluster is the presence of a Fe3S4 cluster, which bridges the nickel and iron atoms together. This cooperative Lewis acid-base pair is considered a key feature for the exceptional activity of Ni-CODHCh II. The long-term goal of this proposal is to employ computational chemistry in combination with complementary experimental efforts to design innovative catalysts that mimic essential structural features and functions of CODH enzymes for the selective conversion of CO2 to CO in the presence of H2O. We propose to accomplish this goal through the following specific aims: (i) To investigate earth-abundant materials supported by macrocyclic redox-active ligands; and (ii) To catalyze the production of carbon monoxide through the use of charged functional groups in the secondary coordination sphere. More specifically, this proposal outlines a plan for the rational design of innovative catalysts for CO2-to-CO conversion based on thermodynamic and kinetic properties. These principles have been established as critical in heterogeneous catalysis. For instance, in the Sabatier principle, the magnitude of the substrate binding energy at the metal in critical intermediates is related to the overall catalyst rate. The use of molecular catalysts will allow us to tune these crucial bond energies in order to achieve optimal values. In this context, electronic structure calculations will provide a straightforward approach to study the key thermodynamic and kinetic properties that are required in the development of molecular catalysts with (i) high selectivity for the desired product; and (ii) fast kinetics over a long period of time. Successful completion of these aims will produce general guidelines based on fundamental thermodynamic and kinetic properties for the design of next generation molecular catalysts for CO2 reduction to CO or any high value C1 product.