C-C Coupling on Single-Atom-Based Heterogeneous Catalyst.

Area of Science:

• Heterogeneous catalysis
• Nanoparticle catalysis
• Organometallic chemistry

Background:

• Homogeneous C-C coupling catalysis faces challenges with catalyst separation and cost.
• Developing efficient heterogeneous catalysts is crucial for sustainable chemical synthesis.
• Titanium dioxide (TiO2) is a versatile material for catalyst support.

Purpose of the Study:

• To develop a highly active and reusable heterogeneous catalyst for Sonogashira C-C coupling reactions.
• To investigate the catalytic performance of single-atom palladium on TiO2 nanoparticles.
• To elucidate the reaction mechanism using density functional theory (DFT) calculations.

Main Methods:

• Synthesis of TiO2-based nanoparticle catalyst anchoring singly dispersed Pd atoms (Pd1/TiO2).
• Testing the catalyst's activity and selectivity across more than 10 Sonogashira C-C coupling reactions.
• Performing DFT calculations to understand the reaction mechanism at the atomic level.

Main Results:

• Pd1/TiO2 demonstrated high activity and selectivity for over 10 Sonogashira coupling reactions.
• A turnover rate of 51.0 diphenylacetylene molecules per Pd atom per minute was achieved at 60 °C.
• A low apparent activation barrier of 28.9 kJ/mol was observed, with no catalyst separation cost.

Conclusions:

• Single-atom palladium on TiO2 nanoparticles (Pd1/TiO2) is an effective heterogeneous catalyst for Sonogashira C-C coupling.
• The catalyst facilitates efficient C-C bond formation with facile separation and reuse.
• DFT calculations revealed a mechanism involving phenyl intermediate adsorbed on Pd1 and phenylacetylenyl on TiO2.