Pd Nanoparticles Supported on Ultrapure ZnO Nanopowders as Reusable Multipurpose Catalysts

Herein, we report the synthesis and application of a highly active and versatile Pd/chemical vapor synthesis-ZnO (Pd/CVS-ZnO) catalytic system. The two-step preparation of the catalyst includes chemical vapor synthesis (CVS) of ultrapure ZnO nanotetrapods, followed by the liquid-phase in situ reduction of a Pd precursor and deposition of polycrystalline Pd nanoparticles (∼6 nm). The as-synthesized catalyst was characterized using standard instrumental techniques. The catalyst was successfully applied in four chemical reactions: Suzuki–Miyaura cross-coupling, reduction of nitroarenes, decarbonylation, and hydrodebromination of aromatic compounds, of which, the latter two are reported for the first time for the Pd/ZnO catalytic system. The catalyst showed excellent activity within a wide range of substrates, delivering the products in high yields (70–99%). The recyclability of the Pd/CVS-ZnO catalyst was tested through two different approaches. First, the catalyst recyclability was examined in all four reactions, reusing the catalyst up to four times in the Suzuki–Miyaura cross-coupling reaction, as well as the reduction of 4-nitrobenzonitrile, without a significant loss of yield. Furthermore, the catalyst was successively used in three different reactions, showing a high degree of stability and delivering excellent product yields in all cases. In addition to its excellent activity, versatility, and stability, the Pd/CVS-ZnO catalytic system also exhibits excellent recyclability over consecutive runs, which makes it a promising candidate for future application in complex industrial processes.