Two-Step Carbothermal Welding To Access Atomically Dispersed Pd₁ on Three-Dimensional Zirconia Nanonet for Direct...

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Developing stable, highly dispersed single-atom catalysts is crucial for efficient chemical transformations.
• Zirconium dioxide (ZrO2) nanostructures offer unique catalytic properties but often suffer from aggregation.
• Nitrogen-doped carbon (NC) can stabilize metal sites but requires effective integration with inorganic supports.

Purpose of the Study:

• To develop a novel carbothermal welding strategy for preparing atomically dispersed palladium (Pd) sites on a 3D ZrO2 nanonet (Pd1@ZrO2).
• To investigate the formation mechanism and catalytic performance of the Pd1@ZrO2 nanonet in indole synthesis.

Main Methods:

• A two-step pyrolysis strategy starting from UiO-66-NH2 metal-organic framework.
• Carbothermal reduction and welding under argon followed by oxidation in air.
• Characterization using various techniques to confirm structure, dispersion, and defects.

Main Results:

• Atomically dispersed Pd sites (Pd1) were successfully anchored on a 3D ZrO2 nanonet via carbothermal welding.
• The process involved transforming N-doped carbon (NC) and ZrO2 nanoclusters, followed by NC gasification and ZrO2 welding.
• Abundant oxygen defects on the ZrO2 nanonet facilitated atom trapping, leading to sintering-resistant Pd1@ZrO2.
• The catalyst exhibited excellent turnover frequency (1109.2 h-1) and 94% selectivity for direct indole synthesis.

Conclusions:

• The carbothermal welding strategy provides a robust method for creating highly stable single-atom catalysts on 3D nanonet supports.
• The Pd1@ZrO2 nanonet demonstrates significant potential as a semi-homogeneous catalyst for organic synthesis, specifically indole production.
• The defect engineering and atom trapping mechanism enhance catalyst longevity and performance.