Strong Electronic Metal-Support Interaction between Iridium Single Atoms and a WO 3 Support Promotes Highly Efficient and Robust CO 2 Cycloaddition.

The carbon dioxide (CO ₂ ) cycloaddition of epoxides to cyclic carbonates is of great industrial importance owing to the high economical values of its products. Single-atom catalysts (SACs) have great potential in CO ₂ cycloaddition by virtue of their high atom utilization efficiency and desired activity, but they generally suffer from poor reaction stability and catalytic activity arising from the weak interaction between the active centers and the supports. In this work, Ir single atoms stably anchored on the WO ₃ support (Ir ₁ -WO ₃ ) are developed with a strong electronic metal-support interaction (EMSI). Superior CO ₂ cycloaddition is realized in the Ir ₁ -WO ₃ catalyst via the EMSI effect: 100% conversion efficiency for the CO ₂ cycloaddition of styrene oxide to styrene carbonate after 15 h at 40 °C and excellent stability with no degradation even after ten reaction cycles for a total of more than 150 h. Density functional theory calculations reveal that the EMSI effect results in significant charge redistribution between the Ir single atoms and the WO ₃ support, and consequently lowers the energy barrier associated with epoxide ring opening. This work furnishes new insights into the catalytic mechanism of CO ₂ cycloaddition and would guide the design of stable SACs for efficient CO ₂ cycloaddition reactions.
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