Green Encapsulation of Palladium on Defective Hierarchical UiO-66 Under Solvent-Free Conditions for Efficient Olefin Hydrogenation Catalyst

Abstract

Highly dispersed palladium nanoparticles (Pd NPs) embedded within a hierarchical UiO-66 structure, referred to as Pd@U-12, have been successfully synthesized via a green, straightforward of solid-solid thermal (SST) method. This innovative SST technique enables uniform dispersion of Pd NPs, allowing their encapsulation within the hierarchical framework of UiO-66. The unsaturated sites in the host UiO-66 facilitate the coordination of Pd, which are subsequently reduced to nanoparticles during the SST process, forming Pd@U-12. The Pd NPs are highly dispersed on the hierarchical support (U-12) and serve effectively as catalytic sites for hydrogenation reactions. The optimally synthesized 20%Pd@U-12 demonstrated exceptional performance as a heterogeneous catalyst for the hydrogenation of cyclohexene, achieving 99% conversion with stable activity over five consecutive cycles. Notably, the SST method for encapsulating Pd NPs (Pd@U-12) offers several advantages, including rapid incorporation of metal nanoparticles within a short time, a green, solvent-free synthesis process, high dispersion and stability of the metal content within the host material. These features could significantly enhance the effectiveness of Pd@U-12 as a robust heterogeneous catalyst in various catalysis applications.