A heterogeneous single-atom palladium catalyst surpassing homogeneous systems for Suzuki coupling

Area of Science:

• Heterogeneous catalysis
• Materials science
• Organic synthesis

Background:

• Palladium-catalyzed cross-coupling reactions are vital in fine-chemical synthesis but face challenges with homogeneous catalysts, including difficult product purification and limited catalyst reusability.
• Previous attempts to immobilize homogeneous catalysts on solid supports often resulted in poor stability, leading to metal leaching and reduced performance.
• Supported palladium nanoparticles, while heterogeneous, often exhibit insufficient activity under mild reaction conditions, risking substrate or product degradation.

Purpose of the Study:

• To develop a novel single-atom heterogeneous catalyst that overcomes the limitations of existing palladium-based catalytic systems.
• To achieve high chemoselectivity and broad functional group tolerance comparable to homogeneous catalysts.
• To demonstrate robust stability and reusability in flow conditions for practical applications in chemical synthesis.

Main Methods:

• Anchoring single palladium (Pd) atoms onto exfoliated graphitic carbon nitride (ECN) to create a single-atom heterogeneous catalyst (Pd-ECN).
• Evaluating the catalytic performance of Pd-ECN in Suzuki coupling reactions.
• Assessing catalyst stability and reusability under flow conditions.

Main Results:

• The Pd-ECN catalyst demonstrated high chemoselectivity and broad functional group tolerance, matching state-of-the-art homogeneous catalysts for Suzuki couplings.
• The catalyst exhibited robust stability in flow, indicating minimal metal leaching or aggregation.
• The adaptive coordination environment within the ECN support structure was shown to facilitate catalytic steps.

Conclusions:

• Single-atom palladium anchored on exfoliated graphitic carbon nitride (Pd-ECN) effectively combines the advantages of homogeneous and heterogeneous catalysis.
• Pd-ECN presents a stable, highly selective, and reusable catalytic system suitable for challenging cross-coupling reactions.
• Nanostructuring single atoms within solid hosts offers a promising strategy for heterogenizing difficult catalytic processes.