Facile one-pot synthesis of superfine palladium nanoparticles on polydopamine-functionalized carbon nanotubes as a nanocatalyst for the Heck reaction

Heterogeneous Pd nanocatalysts are efficient catalysts for the Heck reaction but require multi-step, sophisticated procedures and harsh reaction conditions. In this work, a green and facile strategy has been developed to decorate Pd nanoparticles on polydopamine (PDA)-coated multi-walled carbon nanotubes (Pd/CNTs-PDA) via a one-pot method. The obtained nanoparticles were characterized by various techniques including transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, which proved that Pd NPs are well-dispersed on the PDA and between the surfaces of the PDA and CNTs. The resultant Pd/CNTs-PDA catalysts exhibit excellent catalytic reactivity toward the Heck reaction at low temperatures. Moreover, by DFT simulation, we found that during the PDA polymerization process, a large number of unsaturated -N= and C=O species are more active than the groups on the PDA end product to anchor Pd NPs. The results provide evidence that the catalyst synthesized by the onepot method exhibited good activity because sufficient active sites could be created to effectively promote Pd NPs dispersion during the dopamine polymerization process. Additionally, the Pd/CNTs-PDA catalyst was successfully employed in Heck cross-coupling reactions with various functionalized substrates. This method opens a window for the fabrication of high-performance nanocomposite catalysts under mild conditions using simple methods and has several potential applications. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.