Efficient and green strategy for the chemical conversion and fixation of CO₂ is an attractive topic. In this work, we reported an efficient catalytic system of organic base coupled ionic liquids that could catalyse the synthesis of quinazolinones via cyclization of 2-aminobenzonitriles with CO₂ under mild conditions (e.g., 60 °C, 0.1 MPa). It was found that 1,8-diazabicyclo[5.4.0]undec-7-ene coupled 1-butyl-3-methylimidazole acetate ionic liquids (DBU/[Bmim][OAc]) displayed excellent performance in catalysing the reactions of CO₂ with 2-aminobenzonitriles, and a series of quinazolinones were obtained in high yields at atmospheric pressure. Moreover, the ILs had high stability and reusability, and can be reused at least five times without considerable decrease in catalytic activity. This protocol could also be conducted on a gram scale, and may have promising and practical applications in the production of quinazolinones.