Zeolitic Imidazolate Framework Cores Decorated with Pd Nanoparticles and Coated Further with Metal–Organic Framework Shells (ZIF-8@Pd@MOF-74) as Nanocatalysts for Chemoselective Hydrogenation Reactions

The selective hydrogenation of Ar–C═C in the presence of Ar–NO2 is a long-standing challenge because of the uncontrolled nonselective nature of hydrogenation. In this study, the core–shell nanocatalyst ZIF-8@Pd@MOF-74 is developed for the preferential reduction of the Ar–C═C group. The ZIF-8 core can act as an effective support for Pd nanoparticles (NPs), and the MOF-74 shell can prevent Pd NPs from leaching and oxidation. Compared with Pd/C and ZIF-8@Pd catalysts, our ZIF-8@Pd@MOF-74 nanocatalyst shows enhanced activity and selectivity for conversion of nitrostyrene to 1-ethyl-4-nitrobenzene (>98% yield) without the use of pressured hydrogen, and the turnover frequencies (TOF) can reach 330 h–1. Theoretical and experimental results reveal that the high chemoselectivity is attributed to the preferential adsorption and activation of the Ar–C═C on the MOF-74 shell. Given its outstanding catalytic performance under mild conditions and facile preparation protocol, it would be of considerable interest to develop other MOFs@MNPs@MOFs core–shell nanocatalysts.