Structure evolution of single-site Pt in a metal-organic framework

Area of Science:

• Materials Science
• Catalysis Science
• Nanotechnology

Background:

• Single-atom catalysts (SACs) offer unique catalytic properties due to maximized atom utilization and distinct electronic structures.
• Advanced characterization techniques are crucial for understanding SACs at the atomic scale.
• Metal-organic frameworks (MOFs) provide tunable platforms for anchoring single metal sites.

Purpose of the Study:

• To investigate the structural evolution and activation of isolated single platinum (Pt) sites within a bipyridine-functionalized MOF.
• To elucidate the role of high-temperature helium treatment in Pt activation and carbon monoxide (CO) insertion.
• To correlate structural changes with catalytic activity using advanced spectroscopic and microscopic methods.

Main Methods:

• In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with CO as a probe molecule.
• X-ray photoelectron spectroscopy (XPS) for electronic structure analysis.
• Aberration-corrected scanning transmission electron microscopy (AC-STEM) for atomic-scale imaging.
• Dynamic nuclear polarization-enhanced solid-state nuclear magnetic resonance (DNP-NMR) spectroscopy for structural dynamics.

Main Results:

• High-temperature helium treatment is essential for activating the isolated Pt sites and facilitating CO insertion.
• The study reveals the dynamic structural transformations occurring at the Pt single-atom sites during activation.
• Combined spectroscopic and microscopic data provide a comprehensive understanding of Pt site evolution.

Conclusions:

• The findings highlight the critical role of thermal treatment in preparing and activating Pt SACs within MOFs.
• Understanding the structural evolution is key to designing more efficient single-atom catalysts.
• This work demonstrates the power of combining multiple advanced characterization techniques for atomic-level catalyst research.