Carbon Dioxide Activation Center (CADIAC), Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark.
Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
J Am Chem Soc. 2020 Mar 4;142(9):4265-4275. doi: 10.1021/jacs.9b11806. Epub 2020 Feb 24.
Electrocatalysis is a promising tool for utilizing carbon dioxide as a feedstock in the chemical industry. However, controlling the selectivity for different CO reduction products remains a major challenge. We report a series of manganese carbonyl complexes with elaborated bipyridine or phenanthroline ligands that can reduce CO to either formic acid, if the ligand structure contains strategically positioned tertiary amines, or CO, if the amine groups are absent in the ligand or are placed far from the metal center. The amine-modified complexes are benchmarked to be among the most active catalysts for reducing CO to formic acid, with a maximum turnover frequency of up to 5500 s at an overpotential of 630 mV. The conversion even works at overpotentials as low as 300 mV, although through an alternative mechanism. Mechanistically, the formation of a Mn-hydride species aided by in situ protonated amine groups was determined to be a key intermediate by cyclic voltammetry, H NMR, DFT calculations, and infrared spectroelectrochemistry.
电催化是利用二氧化碳作为化学工业原料的一种很有前途的工具。然而，控制不同 CO 还原产物的选择性仍然是一个主要挑战。我们报告了一系列具有精心设计的联吡啶或菲咯啉配体的锰羰基配合物，如果配体结构含有策略性定位的叔胺，就可以将 CO 还原为甲酸，如果配体中没有胺基或胺基远离金属中心，则可以将 CO 还原为甲酸。经胺基修饰的配合物是用于将 CO 还原为甲酸的最活跃的催化剂之一，在 630 mV 的过电势下，最大周转频率高达 5500 s。即使在 300 mV 的过电势下，转化率也能达到 300 mV，尽管通过的是一种替代机制。通过循环伏安法、1H NMR、DFT 计算和红外光谱电化学，确定了由原位质子化的胺基辅助形成的 Mn-氢化物物种是关键中间体。
