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Division of Labor between Cobalt Nanoparticles and Oxide Supports in Reductive Amination
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DOI：10.1021/acscatal.6c03939.png)
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Abstract
En 中文
Supported metal catalysts dominate heterogeneous catalysis, yet the individual functions of metal nanoparticles and their supports remain largely inferred rather than experimentally isolated. Here, we provide direct mechanistic evidence that oxide supports—not cobalt nanoparticles (Co NPs) themselves—govern the reaction pathway in the reductive amination of aldehydes. Ligand-free hcp-Co NPs synthesized via a hydrosilane-assisted method preferentially catalyze hydrogenation, yielding benzyl alcohol. In striking contrast, when Co NPs are supported on or physically contacted with oxides, the formation of alcohol is completely suppressed and benzylamine is obtained in >90% yield. Systematic spatial-separation experiments reveal that interparticle contact between Co and oxides is essential. Kinetic studies, NH3-TPD analyses, and adsorption experiments demonstrate that oxides strongly promote condensation between aldehydes, ammonia, and in situ amines, thereby generating imines that are subsequently hydrogenated on Co. CO-IR confirms that the electronic structure of Co remains essentially unchanged. These results unambiguously establish that oxides act as condensation promoters rather than electronic modifiers, providing a mechanistic foundation for the rational design of Co-based reductive amination catalysts.
Keywords:
Aldehydes
Catalysts
Condensation
Organic reactions
Oxides
Co nanoparticles
oxide supports
hydrogenation
reductive amination
division of labor
Journal
IF:
13.1
Papers:
1.6W
Citations:
15.0W
Organization
Cited Papers