Bimetallic PdAu Nanoparticles in Amine-Containing Metal-Organic Framework UiO-66 for Catalytic Dehydrogenation of Formic Acid

Ultrafine and well-dispersed PdAu bimetallic nanoparticles (ca. 1.4 nm) are successfully immobilized on amine-containing UiO-66 frameworks (NH2-UiO-66) via a double-solvent impregnation method. By virtue of the double-solvent strategy, the incorporated PdAu nanoparticles (NPs) are mainly present in the alloy state and distributed inside the cavities of NH2-UiO-66 near the window of the cages. The resulting PdAu/UiO-66 catalysts exhibit much higher catalytic activity and stability for the dehydrogenation of formic acid than the catalyst prepared by the conventional single-solvent impregnation method. The composition-optimized Pd0.8Au0.2/UiO-66-D catalyst affords a very high turnover frequency value of 722 h(-1) at 298 K, which is among the highest one in the metal-organic framework-supported Pd-based NP catalysts ever reported under similar reaction conditions. The exceptional catalytic activity and stability of Pd0.8Au0.2/UiO-66-D could be mainly attributed to the formation of highly dispersed PdAu alloy NPs, the suitable electronic structure of Pd species adjusted by the alloy effect, and the metal-support interaction, as well as the abundant amine groups that can promote the activation of the formic acid molecule by forming HCOO- under mild conditions.