The Heptazine-Based Materials through Intrinsically Modification for the Cycloaddition of CO₂ and Bisepoxides

Area of Science:

• Materials Science
• Catalysis
• Green Chemistry

Background:

• Carbon nitride (CN) materials are attractive catalysts for CO2 utilization.
• Efficient conversion of CO2 into valuable products is a key goal in sustainable chemistry.
• Cycloaddition of CO2 with epoxides is a promising route to cyclic carbonates.

Purpose of the Study:

• To design and synthesize heptazine-related carbon nitride materials with varying polymerization degrees.
• To investigate the catalytic performance of these materials in the cycloaddition of CO2 with 1,4-butanediol diglycidyl ether (BDODGE).
• To elucidate the structure-activity relationship and reaction mechanism.

Main Methods:

• Intrinsic modification strategy to design heptazine-related carbon nitride catalysts.
• Catalytic testing of cycloaddition reaction at 140°C for 20 hours.
• Characterization of catalyst properties and analysis of reaction products.
• Proposed reaction mechanism based on experimental results.

Main Results:

• The carbon nitride catalyst prepared at 450°C (CN-450-W), containing melem hydrate, exhibited the best performance.
• Achieved 93.1% epoxide conversion and 99.3% cyclic carbonate selectivity without co-catalyst or solvent.
• High activity attributed to porous structure and synergistic effect of amino and -OH groups; water plays a crucial role.
• The CN-450-W catalyst demonstrated excellent recyclability.

Conclusions:

• Heptazine-related carbon nitride materials are effective catalysts for CO2 cycloaddition with bisepoxides.
• The catalyst prepared at 450°C shows superior performance due to its unique structure and active sites.
• Water is essential for maintaining catalyst structure and activity, enabling efficient and sustainable cyclic carbonate synthesis.