Palladium nanoparticles in situ generated in metal–organic films for catalytic applications

Abstract

Palladium nanoparticles were first in situ generated in metal–organic films for catalytic applications. Layer-by-layer assembly of metal–organic films consisting of rigid-rod chromophores connected by terminal pyridine moieties to palladium centers on solid substrates was presented. Bipyridyl and polypyridyl ligands were used as building blocks to explore the influence of different ligand structures on catalytic properties. Metal–organic films were characterized by UV-Vis spectra, atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results show that the deposition mechanism of metal–organic films is perfect layer-by-layer self-assembling with complete surface coverage and regular growth. Moreover, the catalytic activity toward the hydrogenation of olefin was investigated. Based on XPS and TEM, the catalytic activity toward the hydrogenation of olefin was ascribed to the in situ formation of Pd nanoparticles from Pd ions in metal–organic films. This film material is an active catalyst for the hydrogenation of olefin under mild conditions. Furthermore, catalytic results indicated that monodentate bipyridyl ligands exhibited superior catalytic activity than tridentate polypyridyl ligands. Catalytic activity is related to the loading amount of catalysts and permeability. More importantly, this study points toward the potential application of metal–organic films as heterogeneous catalysts with easy separation and good recyclability.