Biocompatible and recyclable amino acid binary catalyst for efficient chemical fixation of CO2

• Containing active N group and H-bond makes amino acids to be good co-catalyst.
• KI/L-tryptophan is highly efficient and applicable to a variety of epoxides.
• The synergetic catalysis of multiplex active groups was investigated.

In this work, the cycloaddition reactions of CO2 with various epoxides to form five-membered cyclic carbonates catalyzed by an efficient amino acid based biocompatible catalyst were investigated. It was found that the activity of amino acid could be obviously enhanced in the presence of alkali metal salts, and the l-tryptophan catalytic system was the most efficient among the catalysts employed. Based on the result, a possible mechanism for the synergetic effect of catalyst was proposed. The process reported here represents a simple, ecologically safer, cost-effective route to cyclic carbonates with high product quality, as well as easy catalyst recycling.

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