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

Abstract

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.