Modification of silica using piperazine for immobilization of palladium nanoparticles: a study of its catalytic activity as an efficient heterogeneous catalyst for Heck and Suzuki reactions

An efficient heterogeneous palladium catalyst system has been developed based on immobilization of Pd nanoparticles on silica-bonded N-propylpiperazine (SBNPP) substrate. SBNPP substrate can stabilize the Pd nanoparticles effectively so that it can improve their stability against aggregation. Also, grafted piperazine species onto the silica backbone prevents the removing of Pd nanoparticles from the substrate surface. It seems that the high recyclable capability of Pd-SBNPP catalysts is resulted from these two characteristics. Transmission electron microscopy (TEM) of catalyst is shown the size of Pd nanoparticles in Pd-SBNPP average of 20 nm. Furthermore, X-ray photoelectron spectroscopy (XPS) of Pd-SBNPP is shown the presence of Pd(0) in the structure of this catalyst. Overall, TEM, XPS and XRD experiments strongly suggested that Pd nanoparticles were formed and immobilized on silica-functionalized piperazine. The catalytic activity of this catalyst was investigated in the Heck and Suzuki reactions. The catalyst could be recycled several times without appreciable loss in catalytic activity.