触媒反応をリアルタイムで観測する技術（Watch a live catalytic event in real time）

2025-04-12 ノースウェスタン大学

＜関連情報＞

• https://news.northwestern.edu/stories/2025/04/watch-a-live-catalytic-event-in-real-time/
• https://www.cell.com/chem/abstract/S2451-9294(25)00131-7

シングルサイト不均一系触媒反応のメカニズム研究ツールとしての原子分解能イメージング Atomic-resolution imaging as a mechanistic tool for studying single-site heterogeneous catalysis

Yosi Kratish∙ Yiqi Liu∙ Jiaqi Li∙ … ∙ Takayuki Nakamuro∙ Eiichi Nakamura∙ Tobin J. Marks
Chem  Published:April 10, 2025
DOI:https://doi.org/10.1016/j.chempr.2025.102541

Graphical abstract

The bigger picture

Catalysis enormously benefits today’s society—from energy production, fertilizers, advanced materials, and fine chemicals to pharmaceuticals—where heterogeneous catalysts comprise a pivotal 85% of industrial processes. However, unraveling the atomistic intricacies of these processes remains challenging yet essential for creating greener, more atom-efficient next-generation catalysts. Here, we focus on studying the mechanism of sustainable H₂ production via catalytic alcohol dehydrogenation over a single-site carbon-bound MoO₂ catalytic center. We seek to visualize species along the mechanistic pathway through atomic-resolution transmission electron microscopy. Combining those results with data from other complementary experimental and theoretical characterization tools unveils the relationship of key intermediates along the complex dehydrogenation reaction pathway and provides essential clues for enhancing catalytic activity.

Highlights

• Organic intermediate dynamics are observed on the catalyst surface
• EXAFS, XANES, XPS, DFT, and kinetic analyses support the findings
• A new reaction pathway is proposed from experiments and theory

Summary

Heterogeneous catalysts dominate the chemical industry but, unlike homogeneous catalysts, typically feature diverse, incompletely defined active sites. Thus, describing their structure-activity relationships remains challenging. In contrast, molecularly defined single-site heterogeneous catalysts (SSHCs) are poised to address these challenges and provide new avenues for catalysis research and development. The present study explores eco-friendly H₂ production mediated by discrete MoO₂ sites supported on carbon nanohorns (CNHs) and active for alcohol dehydrogenation. Although informative, detailed extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS,) kinetic measurements, and density functional theory (DFT) analysis alone cannot provide a full molecular picture of the reaction pathway. Here, using single-molecule atomic-resolution time-resolved electron microscopy (SMART-EM), we propose the identification of four key catalytic intermediates anchored to CNHs and uncover a new reaction pathway involving alkoxide/hemiacetal equilibration and acetal oligomerization. These intermediates are inferred through a combination of theory and SMART-EM, showcasing the potential of SMART-EM as a complementary tool for exploring mechanistic hypotheses in catalysis.