The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4-Vinyl-Pyridine)

The reactivity of palladium acetate inside a poly(4-vinylpyridine-co-divinylbenzene) polymer is strongly influenced by the establishment of interaction between the Pd precursor and the pyridyl functional group in the polymer. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and simultaneous X-ray absorption near edge structure (XANES) and small angle X-ray scattering (SAXS) techniques have been applied to monitor the reactivity of palladium acetate in the presence of H-2 and CO as a function of temperature. H-2 reduces palladium acetate to Pd nanoparticles and acetic acid. The pyridyl groups in the polymer play a vital role both in stabilizing the formed acetic acid, thus allowing its detection by means of DRIFTS, and the final Pd nanoparticles, which are extremely small and mono-dispersed. On the contrary, CO does not reduce palladium acetate. Rather, it forms Pd2+ carbonyl adducts, which favor the detachment of the acetate ligands and their thermal degradation. These adducts are well observable by means of SAXS because they cause an important local change of the electronic density.