Precise Modulation of Zeolite Acidity by Alkali Metal Ions for Enhancing Catalytic Performance in CO Cycloaddition Reactions.

The CO cycloaddition route is an effective way to achieve efficient conversion and utilization of CO. Zeolites with diverse topologies and tunable acidic sites can efficiently promote the cycloaddition reaction of CO with epoxides. The exchangeable cations in zeolites have a great influence on the performance of the CO cycloaddition, but there are few studies on it. In this paper, the effects of different alkali metal cation (Li, Na, and K)-exchanged zeolites on the cycloaddition reaction of CO were studied to reveal the function of alkali metal cations. The promotion effect of different alkali metal ions on the catalytic performance of the CO cycloaddition reaction gradually increases in the sequence of K < Na < Li. Based on the optimized reaction conditions and zeolite topologies, Li- zeolite could achieve up to 95.99% yield of styrene carbonate, which could still be maintained at as high as 91.67% after five catalytic cycles. The computational results revealed that the ring-opening of styrene oxide is the rate-determining step of the catalytic cycle and Li- has a lower reaction activation energy. This work will further deepen our understanding of the effect of alkali metal ions in zeolite on CO cycloaddition reactions.