Integration of Noble Metal Nanocrystals in a Hollow Metal-Organic Framework Shell

Metal-organic frameworks (MOFs) encapsulatingnoble metalnanocrystals (NCs) have aroused great attention in catalysis, especiallyfor selective catalysis owing to the existence of strong interfacialinteractions and synergistic functions. In noble metal NCs@MOF, thecrystalline framework shell provides the molecular sieving effect,unsaturated metal sites, and functional channels. However, in manycases, it impedes the mass transfer and diffusion of precursors towardnoble metal NCs, thus resulting in suboptimal catalytic performanceand inefficient use of the noble metal catalysts. Integration of noblemetal NCs in a hollow MOF shell could address this concern. Herein,by using ZIF-67 as a self-sacrificial template, we reported a simplestrategy for synthesizing Pd@Hollow ZIF-67. Pre-formed Pd NCs areuniformly confined within a hollow ZIF-67 shell through the dissolutionof the interior of a ZIF-67 sacrificial template and re-growth ofa new ZIF-67 shell due to the competitive coordination of chlorideligands to cobalt ions in ethanol. This method can be easily extendedto fabricate other hollow hybrid materials including Au@Hollow ZIF-67,Pt@Hollow ZIF-67, and sandwich Pd@Hollow ZIF-67. The synthesis ofthese hollow hybrid nanostructures is expected to provide possibilitiesfor the development of a new category of organic-inorganichybrid materials for catalytic applications.

Automated summary

Metal-organic frameworks (MOFs) containing noble metal nanocrystals (NCs) show great potential in catalysis, especially for selective catalysis. However, the crystalline framework shell of MOFs can hinder the mass transfer and diffusion of precursors, leading to suboptimal catalytic performance. The integration of noble metal NCs in a hollow MOF shell can address this issue.