The cycloaddition between CO

2

and epoxides to produce cyclic carbonate is an attractive and efficiency pathway for the utilization of CO

2

as C1 source. The development of catalyst to mediate cycloaddition between CO

2

and epoxides at low temperature and pressure is still a challenge. Herein

a series of polypyrazoles with glass transition temperature (

T

g

) in the range of 42.3–52.5 ℃ were synthesized and served as catalyst to mediate the cycloaddition of CO

2

and epoxides by the assistant of tetrabutylammonium bromide. The catalytic behaviors of polypyrazole on the model cycloaddition of CO

2

to epichlorohydrin

including the reaction parameters optimization and versatility were investigated in detail

and excellent yield (99.9%) and selectivity (99%) were obtained under the optimized reaction conditions of 70 ℃ and 1.0 MPa for 6.0 h. Noteworthily

the polypyrazole acts as homogeneous catalyst during reaction (higher than

T

g

). And under room temperature

polypyrazoles can be easily separated and recovered

which is a promising feature of a heterogeneous catalyst. Furthermore

the reaction mechanism was proposed. The DFT calculation suggested that the formation of hydrogen bond between pyrazole and epoxide greatly reduced the energy barrier

which play an important role in promoting CO

2

cycloaddition.