Surfactant‐Free Palladium Nanoparticles Encapsulated in ZIF‐8 Hollow Nanospheres for Size‐Selective Catalysis in Liquid‐Phase Solution

Abstract

Encapsulation of surfactant‐free Pd nanoparticles (NPs) in the metal–organic framework material ZIF‐8 hollow nanospheres was achieved. Pd@ZIF‐8 hollow nanospheres showed excellent size‐selective catalytic properties in the liquid‐phase hydrogenation of olefins. As a result of the uniform pore size of the ZIF‐8 shell (apertures of 3.4 Å), the catalyst showed high activity for the hydrogenation of 1‐hexene (1.9×8.2 Å) but very low activity for larger molecules such as cis‐cyclooctene (5.3×5.5 Å), trans‐stilbene (4.2×11.3 Å), and triphenylethylene (9.1×9.2 Å). Other surfactant‐free noble‐metal nanoparticles could also be employed to produce NPs@MOFs for catalysis.

Ultrasmall Metal Nanoparticles Confined within Crystalline Nanoporous Materials: A Fascinating Class of Nanocatalysts

“…Moreover, the size, composition and configuration of encapsulated metal clusters can also be controlled according to practical needs. With this method, core–shell structured metal clusters@MOF catalysts can be synthesized for various types of MOFs, such as ZIF‐8, UiO‐66 and MIL‐101. [6d]…”

“…Lu et al reported an effective encapsulation method to incorporate MNPs with various sizes and compositions within ZIF‐8 crystals using PVP as a protective agent. [67c] Typically, the preformed MNP sols were first mixed with an aqueous solution of PVP, and the PVP‐stabilized MNPs were then transferred into the MOF synthetic solution. Because of the surface functionalization with PVP, the size and shape of the MNPs could be easily controlled in the polar solvents during MOF syntheses.…”

“…A) Reproduced with permission. [67c] Copyright 2012, Nature Publishing Group. B) Synthetic route to generate sandwich MIL‐101@Pt@MIL‐101, comprising Pt NPs sandwiched between a core and a shell of MIL‐101.…”

“…Recently, Wang et al reported a surfactant‐free method for the incorporation of Pt NPs within ZIF‐8. [67b] In the synthesis process, the 2‐methyl imidazole played a critical role, acting as both the stabilizer of the NPs and the conjunction linker of ZIF‐8. Without an additional reduction procedure or removal of the surfactant, small Pt NPs with a diameter of ≈2.0 nm were encapsulated within the frameworks of ZIF‐8.…”

Recent Advances of MOFs and MOF‐Derived Materials in Thermally Driven Organic Transformations

“…Compared to supported NPs that are often found on the internal and external MOF surface, completely encapsulating the NPs can offer enhanced activity/selectivity in catalytic reactions ,. For these so‐called core–shell structures, the nanoparticles are typically made before the subsequent MOF synthesis . This smart architecture provides a convenient way to afford desired molecules, because the identity and orientation of the approaching substrate is strongly influenced by the MOF pore architecture.…”