Ionic-Liquid-Functionalized UiO-66 Framework: An Experimental and Theoretical Study on the Cycloaddition of CO₂ and...

Area of Science:

• Materials Science
• Catalysis
• Green Chemistry

Background:

• Metal-organic frameworks (MOFs) like UiO-66-NH2 offer tunable properties for catalysis.
• Ionic liquids (ILs) can enhance catalytic activity and selectivity.
• Efficient CO2 utilization is crucial for sustainable chemistry.

Purpose of the Study:

• To develop novel bifunctional heterogeneous catalysts for epoxide cycloaddition with CO2.
• To investigate the synergistic effects of ILs and MOFs in catalysis.
• To elucidate the reaction mechanism using computational methods.

Main Methods:

• Modification of UiO-66-NH2 with imidazolium-based ionic liquids (ILA and ILB) via condensation.
• Catalytic testing of the synthesized ILA@U6N and ILB@U6N catalysts for CO2 cycloaddition.
• CO2 adsorption capability assessment.
• Periodic Density Functional Theory (DFT) calculations for mechanistic studies.

Main Results:

• The synthesized ILA@U6N and ILB@U6N catalysts demonstrated excellent CO2 adsorption and catalytic activity.
• ILA@U6N showed superior performance in the cycloaddition of epoxides to CO2, producing cyclic carbonates under mild, solvent-free conditions.
• Enhanced activity was attributed to the synergistic effect between Lewis acidic Zr4+ centers and Br- ions.
• A detailed DFT study provided insights into reaction intermediates, transition states, and pathways.

Conclusions:

• The facile modification of UiO-66-NH2 with ILs yields effective bifunctional heterogeneous catalysts.
• The developed catalysts offer a promising route for sustainable CO2 utilization in cyclic carbonate synthesis.
• The study highlights the importance of catalyst design and computational methods for understanding catalytic mechanisms.