Polymetric pseudo liquid behavior of ionic cyclic polypyrazoles for efficient CO2 cycloaddition reaction under mild conditions.

A sustainable and green system of "heating pseudoliquid catalysis and cooling heterogeneous recovery" is constructed by cyclic polypyrazoles integrated with bromoethane, and used for efficient and stable cycloaddition of CO 2. [Display omitted] • Cyclic polypyrazoles integrated with bromoethane with low glass transition temperature. • Ionic cyclic polypyrazoles for efficient CO 2 cycloaddition with epoxides under mild conditions. • Sustainable and green system of "heating pseudoliquid catalysis and cooling heterogeneous recovery. The capture and conversion of CO 2 into value-added chemicals has become an imminent research topic in both scientific and industrial area. The cycloaddition of CO 2 with C1 resource such as epoxides to produce cyclic carbonates is an promising and efficiency pathway for CO 2 utilization. The development of catalyst for CO 2 cycloaddition with epoxides at low pressure is still a challenge. Herein, we reported the preparation of cyclic polypyrazoles integrated with bromoethane, which can serve as hydrogen bonding donor and nucleophilic groups, respectively, for activation of the epoxides and subsequent cycloaddition of CO 2. The as-obtained ionic cyclic polypyrazoles (ICPP) could exist in the form of polymetric pseudo liquid during reaction and then turns into heterogenous state after reaction due to the low glass transition temperature. By changing the reaction temperature and ratio of catalyst to epoxides, an optimized performance which show a epoxides conversion over 90 % and a selectivity of 99 % to cyclic carbonate was realized under 0.1 MPa in the absence of cocatalysts and additives. The catalyst can be facilely recovered due to its high stability, and no obvious decrease in conversion was observed after five successive runs. This work provides a sustainable and green process for CO 2 cycloaddition, and also highlights the potential of using ionic cyclic polypyrazole for conversion of CO 2 into value-added chemicals. [ABSTRACT FROM AUTHOR]