Charge Separation in Metal-Organic Framework Enables Heterogeneous Thiol Catalysis

Area of Science:

• Materials Science
• Catalysis
• Photochemistry

Background:

• Heterogeneous catalysis offers advantages in product separation and catalyst recyclability.
• Metal-organic frameworks (MOFs) are promising materials for catalysis due to their tunable structures and high surface areas.
• Radical catalysis enables unique chemical transformations but often requires specific initiation methods.

Purpose of the Study:

• To develop a novel photoinduced heterogeneous catalyst for thiol-mediated reactions.
• To investigate the mechanism of radical generation and catalysis within a MOF structure.
• To demonstrate the practical applicability of this new catalytic system.

Main Methods:

• Synthesis and characterization of the metal-organic framework Zr-TPDCS-1.
• Photochemical irradiation of the MOF in the presence of various organic substrates and boron, silicon, phosphorus, and sulfur sources.
• Control experiments to elucidate the reaction pathway and radical generation.
• Gram-scale reaction optimization and product isolation.

Main Results:

• The MOF Zr-TPDCS-1 effectively catalyzed borylation, silylation, phosphorylation, and thiolation reactions upon photoirradiation.
• Evidence suggests that light induces electron transfer within the MOF, generating thiyl radicals that initiate catalysis.
• Control experiments confirmed the involvement of thiyl radicals and a radical reaction pathway.
• Gram-scale reactions achieved high efficiency with convenient product separation and a turnover number of approximately 3880.

Conclusions:

• Photoinduced MOF-enabled heterogeneous thiol catalysis is achieved for the first time.
• The MOF Zr-TPDCS-1 acts as an efficient photocatalyst for various element radical generation and subsequent organic transformations.
• The demonstrated high turnover number and ease of product separation highlight the significant potential for practical applications in heterogeneous radical catalysis.