Dynamic Confinement Approach for High Metal Loading Single-Atom Catalysts Based on Covalent Organic Frameworks

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Single-atom catalysts (SACs) provide well-defined active sites but face challenges in achieving high metal loadings without aggregation.
• Developing stable SACs with high metal content is crucial for advanced catalytic applications.

Purpose of the Study:

• To develop a synthetic strategy for ultra-high metal loading single-atom catalysts.
• To investigate the use of palladium polyphthalocyanine covalent organic frameworks (COFs) for high-performance catalysis.
• To explore the role of dynamic confinement in stabilizing single-atom catalysts.

Main Methods:

• Synthesized palladium polyphthalocyanine COFs using a mixed metal ionothermal approach with PdCl2/ZnCl2 or PdCl2/ZnCl2/NaCl.
• Employed theoretical simulations to understand the dynamic confinement of palladium atoms within the COF framework.
• Evaluated catalyst performance under continuous flow conditions over 24 hours.

Main Results:

• Achieved ultra-high palladium loadings up to 22.2 wt% in COFs with atomically dispersed Pd ions.
• Demonstrated that the crystalline framework dynamically confines Pd atoms, preventing dimerization and ensuring long-term stability.
• Catalysts exhibited stable performance with yields up to 90% in continuous flow reactions.

Conclusions:

• The developed synthetic strategy enables ultra-high metal loading SACs.
• Dynamic confinement within crystalline organic supports is key to achieving stable and high-performing SACs.
• This work sets a new benchmark for SACs and offers a promising approach for catalyst design.