Spectroscopic identification of acid-base pairs in solid catalysts

Area of Science:

• Catalysis
• Materials Science
• Spectroscopy

Background:

• Solid catalysts often rely on both acidic and basic sites for their function.
• Understanding the spatial arrangement of these acid-base pairs is crucial for catalyst performance.
• Previous methods lacked the resolution to precisely characterize these interactions.

Purpose of the Study:

• To systematically characterize acid-base pairs in solid catalysts.
• To reveal the spatial correlations between acidic and basic sites.
• To guide the rational design of bifunctional acid-base catalysts.

Main Methods:

• Utilized advanced two-dimensional homonuclear or heteronuclear correlation solid-state nuclear magnetic resonance (NMR) spectroscopy.
• Employed pyridine-d5 or trimethylphosphine as probes for acid sites.
• Used pyrrole as a probe for base sites, co-adsorbing probes onto the catalyst surface.

Main Results:

• Successfully established the spatial proximity of probe molecules representing acid and base sites.
• Demonstrated the capability of 2D ssNMR to reveal spatial correlations in acid-base pairs.
• Provided detailed characterization of the acid-base site landscape on solid catalysts.

Conclusions:

• The study successfully characterized acid-base pairs in solid catalysts using advanced 2D ssNMR.
• The findings highlight the importance of spatial proximity for bifunctional catalyst design.
• This methodology offers a powerful tool for optimizing catalyst performance.