Quantifying Microenvironment Effect on Metal Electronic Structure With Experimentally Accessible Descriptor: Examples...

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• The chemical microenvironment significantly influences metal nanoparticle (NP) electronic structures.
• Current understanding of these effects is largely qualitative due to a lack of quantitative descriptors.

Purpose of the Study:

• To develop a quantitative descriptor for the electronic influence of metal-organic frameworks (MOFs) on incorporated platinum nanoparticles (Pt NPs).
• To correlate this descriptor with catalytic activity in ammonia borane methanolysis.

Main Methods:

• Synthesis of reticular MOFs (MIP-206-X) with varying functional groups.
• Incorporation of Pt NPs into MOFs to create Pt@MIP-206-X.
• X-ray absorption near edge structure (XANES) to determine Pt d-orbital occupancy.
• Quantification of electronic contribution as Δe.
• Isotopic analyses and DFT calculations.

Main Results:

• The descriptor Δe accurately quantifies the electronic contribution from MOFs to Pt NPs.
• Δe shows a strong linear correlation with catalytic activity for ammonia borane methanolysis.
• A larger Δe enhances methanol adsorption on Pt, facilitating O─H bond cleavage as the rate-determining step (RDS).

Conclusions:

• The developed descriptor Δe provides a quantitative measure of the MOF's electronic impact on Pt NPs.
• This descriptor enables accurate prediction and optimization of catalytic performance.
• The study elucidates the mechanism of enhanced activity through strengthened methanol adsorption and promoted O─H bond cleavage.