An interfacial etching approach was developed for the synthesis of monodisperse and ultrasmall thiolated palladium nanoclusters (Pd NCs) using Zr-UiO-66-NH₂ metal–organic frameworks (MOFs) as sacrificial templates. The Pd NCs were originally synthesized inside the cavities of the MOFs (Pd@UiO-66-NH₂). The Pd NCs released from the MOFs have a strikingly small size with narrow distribution (1.1±0.1 nm), amounting to a cluster size of ca. 40 Pd atoms. The ¹H NMR spectrum indicates that thiol is the only capping agent for these Pd NCs. We derived the composition of the thiolated Pd NCs using thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. Moreover, the Pd NCs size can be tuned by using MOF templates with different cavity sizes. The thiolated Pd NCs are catalytically active in a model Suzuki–Miyaura coupling reaction.

The host–guest interaction between metal ions (Pt²⁺ and Cu²⁺) and a zirconium metal–organic framework (UiO-66-NH₂) was explored using dynamic nuclear polarization-enhanced ¹⁵N{¹H} CPMAS NMR spectroscopy supported by X-ray absorption spectroscopy and density functional calculations. The combined experimental results conclude that each Pt²⁺ coordinates with two NH₂ groups from the MOF and two Cl⁻ from the metal precursor, whereas Cu²⁺ do not form chemical bonds with the NH₂ groups of the MOF framework. Density functional calculations reveal that Pt²⁺ prefers a square-planar structure with the four ligands and resides in the octahedral cage of the MOF in either cis or trans configurations.

To establish the structure–catalytic property relationships of heterogeneous catalysts, a detailed characterization of the three-dimensional (3D) distribution of active sites on a single catalyst is essential. Single-particle catalysis of a modular multilayer catalytic platform that consists of a solid silica core, a mesoporous silica shell, and uniformly distributed Pt nanoparticles sandwiched in between these layers is presented. The first 3D high-resolution super-localization imaging of single fluorescent molecules produced at active sites on the core-shell model nanocatalysts is demonstrated. The 3D mapping is aided by the well-defined geometry and a correlation study in scanning electron microscopy and total internal reflection fluorescence and scattering microscopy. This approach can be generalized to study other nano- and mesoscale structures.

To establish the structure–catalytic property relationships of heterogeneous catalysts, a detailed characterization of the three-dimensional (3D) distribution of active sites on a single catalyst is essential. Single-particle catalysis of a modular multilayer catalytic platform that consists of a solid silica core, a mesoporous silica shell, and uniformly distributed Pt nanoparticles sandwiched in between these layers is presented. The first 3D high-resolution super-localization imaging of single fluorescent molecules produced at active sites on the core-shell model nanocatalysts is demonstrated. The 3D mapping is aided by the well-defined geometry and a correlation study in scanning electron microscopy and total internal reflection fluorescence and scattering microscopy. This approach can be generalized to study other nano- and mesoscale structures.

We report the synthesis, structural characterization, thermal stability study, and regeneration of nanostructured catalysts made of 2.9 nm Pt nanoparticles sandwiched between a 180 nm SiO₂ core and a mesoporous SiO₂ shell. The SiO₂ shell consists of 2.5 nm channels that are aligned perpendicular to the surface of the SiO₂ core. The nanostructure mimics Pt nanoparticles that sit in mesoporous SiO₂ wells (Pt@MSWs). By using synchrotron-based small-angle X-ray scattering, we were able to prove the ordered structure of the aligned mesoporous shell. By using high-temperature cyclohexane dehydrogenation as a model reaction, we found that the Pt@MSWs of different well depths showed stable activity at 500 °C after the induction period. Conversely, a control catalyst, SiO₂-sphere-supported Pt nanoparticles without a mesoporous SiO₂ shell (Pt/SiO₂), was deactivated. We deliberately deactivated the Pt@MSWs catalyst with a 50 nm deep well by using carbon deposition induced by a low H₂/cyclohexane ratio. The deactivated Pt@MSWs catalyst was regenerated by calcination at 500 °C with 20 % O₂ balanced with He. After the regeneration treatments, the activity of the Pt@MSWs catalyst was fully restored. Our results suggest that the nanostructured catalysts—Pt nanoparticles confined inside mesoporous SiO₂ wells—are stable and regenerable for treatments and reactions that require high temperatures.