Controlled synthesis of metal-organic frameworks coated with noble metal nanoparticles and conducting polymer for enhanced catalysis

Abstract

The combination of noble metal nanoparticles (NM NPs) and metal-organic frameworks (MOFs) for enhanced properties in catalysis is a rapidly developing interdisciplinary research field. Herein we report a facile one-step approach to the deposition of functional nanocomposite shell composed of NM NPs and conducting polymer on the surface of particulate UiO-66. Our approach is based on the recently developed double solvents method involving a hydrophobic solvent (n-hexane) and a hydrophilic solvent (water). Particularly, the n-hexane was used in a large amount to suspend the UiO-66 particles with hydrophilic inner pores and promoted the enrichment of the water containing the palladium chloride (PdCl2) inside the pores of UiO-66 particles, because these two solvents are immiscible and the volume of water is smaller than the pore volume of the UiO-66 particles. After the introduction of hydrophobic pyrrole into the n-hexane, the UiO-66 particles are successfully coated with a nanocomposite shell, composed of Pd NPs and polypyrrole (PPy) resulting from the interfacial polymerization of pyrrole on the external surface of UiO-66 particles initiated by PdCl2 presented within the UiO-66 particles. Significantly, in such a unique structure, the prepared hybrid particles noted as UiO-66/Pd@PPy nanocomposite particles are demonstrated to be an excellent catalyst with both high activity and stability in the reduction reaction of p-nitrophenol and sodium borohydride. Furthermore, this synthetic method not only effectively controls the mass loading of Pd NPs and PPy on the UiO-66 particles but also enables the deposition of Au@PPy and Ag@PPy nanocomposite shells onto the surface of the UiO-66 particles.