CO2 reduction by a Mn electrocatalyst in the presence of a Lewis acid: a DFT study on the reaction mechanism
CO2 reduction by a Mn electrocatalyst in the presence of a Lewis acid: a DFT study on the reaction mechanism
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DOI：
10.1039/c9se00213h
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发表时间：
2019-07-01
影响因子：
5.6
通讯作者：
Sharma, Akhilesh K.
中科院分区：
文献类型：
--
作者：
Isegawa, Miho;Sharma, Akhilesh K.
加入刘易斯酸（Mg 2+）已被证明可提高均相电催化剂还原CO2的效率。最近，报道了涉及在Mg（OTf）（2）存在下具有大体积联吡啶配体[Mn（mesbpy）（CO）（3）MeCN]（mesbpy = 6，6 ′-二均三甲苯基-2，2 ′-联吡啶）的Mn电催化剂的CO2还原方案（Sampson等人，J. Am.化学会，2016，138，1386-1393）。然而，缺乏对该反应的详细机理理解。在这里，我们提出的反应机理的基础上，来自密度泛函理论（DFT）计算的热力学和动力学数据的细节。密度泛函理论计算表明，Mg（OTf）（2）的主要作用是通过刘易斯对结合稳定两电子还原的Mn中间体.此外，Mg（OTf）（2）使得反应在化学上和动力学上可行。在我们提出的机制中，两个分子CO2和Mg（OTf）（2）有助于C-O键断裂反应。Mg（OTf）（2）在该催化过程中的作用对于设计用于在温和反应条件下转化CO2的新型多金属催化剂具有重要意义。
The addition of a Lewis acid (Mg2+) has been shown to improve the efficiency of CO2 reduction by homogeneous electrocatalysts. Recently, a CO2 reduction protocol involving a Mn electrocatalyst with a bulky bipyridine ligand [Mn(mesbpy)(CO)(3) MeCN](mesbpy = 6,6 '-dimesityl-2,2 '-bipyridine) in the presence of Mg(OTf)(2) was reported (Sampson et al., J. Am. Chem. Soc., 2016, 138, 1386-1393). However, a detailed mechanistic understanding of this reaction is lacking. Here we present the details of the reaction mechanism based on thermodynamic and kinetic data derived from density functional theory (DFT) calculations. The DFT calculations demonstrate that the primary role of Mg(OTf)(2) is to stabilize a two-electron reduced Mn intermediate through Lewis pair binding. Furthermore, Mg(OTf)(2) makes the reaction thermodynamically and kinetically feasible. In our presented mechanism, two molecules of CO2 and Mg(OTf)(2) contribute to the C-O bond cleavage reaction. The demonstrated roles of Mg(OTf)(2) in this catalytic process are important for the design of novel multimetallic catalysts for CO2 conversion under milder reaction conditions.