Amine-functionalized metal-organic frameworks loaded with Ag nanoparticles for cycloaddition of CO2 to epoxides

With the advantages of low raw material cost and 100% atom utilization, the synthesis of high value-added chemical product cyclic carbonates by the cycloaddition of CO₂ to epoxides has become one of the most prospective approaches to achieve the industrial utilization of CO₂. In the reported catalytic systems, the complexity of the catalyst synthesis process, high cost, separation difficulties, and low CO₂ capture limit the catalytic efficiency and its large-scale application. In this paper, Ag nanoparticles loaded on polyethyleneimine (PEI)-modified UiO-66-NH₂ (Ag/PEI@UiO-66-NH₂) are successfully synthesized by in situ immersion reduction. The Ag nanoparticles and the amino groups on the surfaces of PEI@UiO-66-NH₂ contribute to the adsorption of CO₂ and polarization of C–O bonds in epoxides, thereby boosting the conversion capability for the CO₂ cycloaddition reaction. At the amount of propylene oxide of 0.25 mol and the catalyst dosage of 1% of the substrate, the yield and selectivity of propylene carbonate are up to 99%. In addition, the stability and recyclability of Ag/PEI@UiO-66-NH₂ catalyst are attained. The Ag/PEI@UiO-66-NH₂ catalyst also demonstrates a wide range of activity and distinctive selectivity toward cyclo-carbonates in the cycloaddition of CO₂ to epoxides. This work provides a guide to designing a highly efficient catalyst for in situ capture and high-value utilization of CO₂ in industrial applications.