Catalytic performance of palladium nanoparticles encapsulated within nitrogen-doped carbon during Heck reaction

Abstract The Confinement effect is an effective strategy for enhancing the performance of catalysts during various reactions. We developed a strategy to encapsulating Palladium nanoparticles with a dopamine-derived N-doped multilayer carbon shell to catalyze the Heck reaction between iodobenzene and carbon–carbon double-bond compounds (styrene and methyl acrylate). The catalytic performances of Pd nanoparticles encapsulated within a N-doped carbon layer (Pd@N-C) and those attached to the external surface of such a layer (Pd/N-C) were evaluated and compared. Pd@N-C exhibited a lower reaction activation energy (78 kJ/mol) than that of Pd/N-C (106 kJ/mol). Thus, the activity of Pd@N-C during the Heck reaction between iodobenzene and methyl acrylate was approximately 20 times higher than that of Pd/N-C-200. The results of thermal filtration and recycling tests indicated that Pd@N-C showed a lower degree of leaching than that of Pd/N-C-200 owing to the spatial restriction effect of the cavity in the case of the former. Hence, the superior catalytic performance of Pd@N-C can be ascribed to the confinement of the Pd nanoparticles within the N-doped carbon layer. Finally, we used these catalysts to synthesize a range of para-substituted iodobenzene derivatives, thus demonstrating the potential of Pd-encapsulating catalysts for use in the Heck reaction on the technical scale.