Droplet-Based Microfluidics Reveals Insights into Cross-Coupling Mechanisms over Single-Atom Heterogeneous Catalysts

Area of Science:

• Catalysis
• Materials Science
• Organic Chemistry

Background:

• Single-atom heterogeneous catalysts (SACs) are promising sustainable alternatives to metal complexes for organic transformations.
• Understanding the working structure and dynamics of SACs is crucial for catalyst design but remains challenging.
• Suzuki-Miyaura cross-coupling is a vital organic transformation where SACs could offer advantages.

Purpose of the Study:

• To investigate the in-situ working structure and catalytic mechanism of a palladium SAC in Suzuki-Miyaura cross-coupling.
• To compare the electronic structure of active palladium centers in SACs with homogeneous systems.
• To elucidate the role of ligands and bases in stabilizing the active sites of palladium SACs.

Main Methods:

• Utilized droplet-based microfluidics for in-situ reaction monitoring.
• Employed X-ray absorption spectroscopy (XAS) to probe the electronic structure of palladium.
• Investigated a palladium SAC supported on exfoliated carbon nitride.

Main Results:

• Confirmed a surface-catalyzed mechanism for the Suzuki-Miyaura cross-coupling reaction using the palladium SAC.
• Revealed distinct electronic structures of active palladium centers in the SAC compared to homogeneous palladium complexes.
• Gained insights into the stabilizing effects of ligands and bases on the palladium SAC.

Conclusions:

• Established a valuable framework for the in-situ mechanistic study of SACs in organic synthesis.
• Demonstrated the potential of palladium SACs as efficient and sustainable catalysts for Suzuki-Miyaura cross-coupling.
• Highlighted the importance of understanding catalyst structure and dynamics for advancing SAC design.