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Pendant Hydrogen-Bond Donors in Cobalt Catalysts Independently Enhance CO2 Reduction
ACS Central Science ( IF 12.7 ) Pub Date : 2018-02-23 00:00:00 , DOI: 10.1021/acscentsci.7b00607
Alon Chapovetsky 1 , Matthew Welborn 2 , John M. Luna 1 , Ralf Haiges 1 , Thomas F. Miller 2 , Smaranda C. Marinescu 1
Affiliation  

The bioinspired incorporation of pendant proton donors into transition metal catalysts is a promising strategy for converting environmentally deleterious CO2 to higher energy products. However, the mechanism of proton transfer in these systems is poorly understood. Herein, we present a series of cobalt complexes with varying pendant secondary and tertiary amines in the ligand framework with the aim of disentangling the roles of the first and second coordination spheres in CO2 reduction catalysis. Electrochemical and kinetic studies indicate that the rate of catalysis shows a first-order dependence on acid, CO2, and the number of pendant secondary amines, respectively. Density functional theory studies explain the experimentally observed trends and indicate that pendant secondary amines do not directly transfer protons to CO2, but instead bind acid molecules from solution. Taken together, these results suggest a mechanism in which noncooperative pendant amines facilitate a hydrogen-bonding network that enables direct proton transfer from acid to the activated CO2 substrate.

中文翻译:

钴催化剂中悬挂的氢键供体独立地提高了CO 2的还原

生物启发的将质子侧链供体掺入过渡金属催化剂是将环境有害的CO 2转化为高能产物的一种有前途的策略。但是,对这些系统中质子转移的机理了解甚少。在本文中,我们提出了一系列在配体框架中具有变化的侧链仲和叔胺的钴配合物,目的是解开第一和第二配位球在CO 2还原催化中的作用。电化学和动力学研究表明,催化速率显示出对酸,CO 2的一级依赖性,和侧链仲胺的数量。密度泛函理论研究解释了实验观察到的趋势,并表明侧链仲胺不会将质子直接转移到CO 2上,而是会结合溶液中的酸分子。综上所述,这些结果表明了一种机制,其中不合作的侧基胺促进氢键网络,该网络使质子能够从酸直接转移到活化的CO 2底物上。
更新日期:2018-02-23
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