Calcium single atoms stabilized by nitrogen coordination in metal-organic frameworks as efficient solid base...

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Single-atom solid base catalysts (SASBCs) offer high activity and site utilization.
• Existing SASBC fabrication methods require high temperatures, leading to metal sublimation and support damage.
• Developing low-temperature synthesis routes for SASBCs is crucial.

Purpose of the Study:

• To develop a novel, low-temperature method for synthesizing single-atom solid base catalysts.
• To immobilize alkaline earth metal calcium (Ca) sites onto a nitrogen-rich metal-organic framework (UiO-67-BPY).
• To investigate the catalytic performance and stability of the synthesized Ca-based SASBC in base-catalyzed reactions.

Main Methods:

• Fabrication of Ca single-atom catalyst (Ca₁/UiO-67-BPY) by immobilizing Ca onto UiO-67-BPY at room temperature.
• Characterization of the catalyst's atomic structure, confirming Ca single atoms coordinated by two nitrogen atoms.
• Evaluation of the catalyst's performance in the Knoevenagel reaction between benzaldehyde and malononitrile.

Main Results:

• The Ca₁/UiO-67-BPY catalyst was successfully synthesized at room temperature.
• The catalyst exhibited an ordered structure with Ca single atoms anchored by framework nitrogen atoms.
• Achieved a high product yield of 87.2% in the Knoevenagel reaction.
• Demonstrated good catalytic stability over multiple reaction cycles.

Conclusions:

• A novel, low-temperature synthesis strategy for SASBCs was established.
• The Ca₁/UiO-67-BPY catalyst shows significant potential for base-catalyzed reactions due to its high activity and stability.
• This work provides new insights for designing efficient SASBCs for various catalytic applications.