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

Zhao, Yaqian, Li, Yunxing, Pang, Huan, Yang, Cheng, Ngai, To
Journal of colloid and interface science 2019 v.537 pp. 262-268
borohydrides, catalysts, catalytic activity, coordination polymers, hexane, hydrophilicity, hydrophobicity, interdisciplinary research, nanocomposites, nanoparticles, p-nitrophenol, palladium, polymerization, pyrroles, sodium, solvents
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.