A MOF@MOF S-scheme Heterojunction with Lewis Acid-Base Sites Synergistically Boosts Cocatalyst-Free CO₂ Cycloaddition

Area of Science:

• Materials Science
• Catalysis
• Green Chemistry

Background:

• Photocatalytic cycloaddition of CO2 and epoxides is a key strategy for CO2 utilization.
• Development of high-performance photocatalysts is crucial for efficient CO2 conversion.
• Existing photocatalysts often require co-catalysts, limiting their practical application.

Purpose of the Study:

• To design and synthesize a novel S-scheme heterojunction photocatalyst for CO2 cycloaddition.
• To investigate the mechanism of the photocatalytic reaction and the role of active sites.
• To achieve high yield and efficiency in CO2 utilization without co-catalysts.

Main Methods:

• Construction of an S-scheme heterojunction: MIL-125@ZIF-67 modified by amino groups.
• In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for reaction monitoring.
• In-situ electron paramagnetic resonance (EPR) spectroscopy to study reaction intermediates and mechanisms.

Main Results:

• Achieved a cyclic carbonate yield of 99% without any co-catalyst.
• Demonstrated efficient photogenerated electron migration from Lewis acid (Co) sites to epoxide.
• Showcased activation of CO2 by Lewis base (amino groups) sites, facilitating cycloaddition.

Conclusions:

• The developed MIL-125@ZIF-67 photocatalyst exhibits superior performance for CO2 cycloaddition.
• Synergistic effects of dual-active sites (Lewis acid and Lewis base) enhance catalytic activity.
• This work provides a promising strategy for designing efficient heterogeneous photocatalysts for CO2 utilization.