Molecular Cobalt Complexes with Pendant Amines for Selective Electrocatalytic Reduction of Carbon Dioxide to Formic Acid

作者：Souvik Roy, Bhaskar Sharma, Jacques Pécaut, Philippe Simon, Marc Fontecave, Phong D. Tran, Étienne Derat, Vincent Artero · 发表于：Journal of the American Chemical Society · 年份：2017 · DOI：10.1021/jacs.6b11474 · 被引用次数：348 · 研究领域：Carbon dioxide utilization in catalysis、CO2 Reduction Techniques and Catalysts、Asymmetric Hydrogenation and Catalysis

We report here on a new series of CO 2 -reducing molecular catalysts based on Earth-abundant elements that are very selective for the production of formic acid in dimethylformamide (DMF)/water mixtures (Faradaic efficiency of 90 ± 10%) at moderate overpotentials (500–700 mV in DMF measured at the middle of the catalytic wave). The [CpCo(P R 2 N R ′ 2 )I] + compounds contain diphosphine ligands, P R 2 N R ′ 2, with two pendant amine residues that act as proton relays during CO 2 -reduction catalysis and tune their activity. Four different P R 2 N R′ 2 ligands with cyclohexyl or phenyl substituents on phosphorus and benzyl or phenyl substituents on nitrogen were employed, and the compound with the most electron-donating phosphine ligand and the most basic amine functions performs best among the series, with turnover frequency >1000 s –1 . State-of-the-art benchmarking of catalytic performances ranks this new class of cobalt-based complexes among the most promising CO 2 -to-formic acid reducing catalysts developed to date; addressing the stability issues would allow further improvement. Mechanistic studies and density functional theory simulations confirmed the role of amine groups for stabilizing key intermediates through hydrogen bonding with water molecules during hydride transfer from the Co center to the CO 2 molecule.