One-Pot synthesis of amino acid-based functional hyper-crosslinked ionic polymers as heterogeneous catalysts for efficient fixation of CO2 with epoxides

Abstract

The exploitation of multifunctional heterogeneous catalysts for efficient CO2 fixation has been an urgent task in recent years. Herein, three novel amino acid-based hyper-crosslinked ionic polymers (HIPs) with different pendant groups have been constructed via simultaneously Friedel-Crafts alkylation and quaternization reactions in a one-pot manner. The obtained HIPs showed a luxuriant meso/microporous morphology and perfect thermal and chemical stability that are of great importance for practical application. Furthermore, they also showed an excellent CO2 uptake capacity up to 25.17 cm3/g that benefits from N-rich porphyrin units and the amino pendant in the polymer skeleton. Meanwhile, the obtained amino acid-based HIPs can efficiently catalyze the cycloaddition of various epoxides with CO2 under mild conditions without solvents, cocatalysts, and transition metals. Among them, the HIP-His-1 shows the best performance to achieve 99 % product yield with 99 % selectivity for pure CO2 and can also convert diluted CO2 (15 %CO2 and 85 %N2) with satisfactory performance. Moreover, it also shows an exciting reusability which can maintain 91 % of its catalytic yield and 99 % of the selectivity after 5 cycles. The cooperative effects of hydrogen-bond donors (HBDs) and nucleophilic anions during the catalytic process are proposed based on theoretical calculations and this will provide new inspiration for the design and application of HIPs on CO2 conversion.