Pd–PPy nanocomposite on the surface of carbon nanotubes: synthesis and catalytic activity

摘要

In the presence of carbon nanotubes (CNTs), palladium (Pd)–polypyrrole (PPy)@CNT nanocomposites have beenrnsynthesized by way of one-pot and one-step colloidal synthesis from a solution of a palladium inorganic salt and organicrnpyrrole as monomeric precursor to PPy. This efficient method leads to the growth of nanoparticles of the palladiumrninorganic component distributed inside a polymer matrix supported on CNTs. After characterization, palladium–PPy@CNTrnnanocomposites have been employed as efficient heterogeneous catalysts for direct C–H bond functionalization towardrnC–C bond coupling formation. The notable catalytic activity of the palladium–PPy@CNT nanocomposite decreased withrnsuccessive catalytic cycles when using the same portion of the composite. This was attributed to palladium redistributionrninside the PPy matrix, which occurs by way of a specific mechanism involving the reaction solvent and the compositernduring C–C coupling reaction. This mechanism is recrystallization of palladium nanoparticles in conductive PPy matrix.rnNevertheless, the use of palladium–PPy@CNT nanocomposite in first cycle of investigated catalytic reaction facilitates C-Crnbond coupling formation: reaction occurs at lower temperature in comparison with homogeneous catalysts.