Efficient conversion of CO2 into quinazoline-2,4(1H,3H)-diones by glutarimide-based ionic liquids: Relationship among catalytic activity, CO2 absorption capacity, and the interaction force of cations and anions

Abstract

The harsh reaction condition, especially for the high carbon dioxide (CO₂) pressure, is an obstacle for the carboxylation cyclization reaction of CO₂ with 2-aminobenzonitrile due to the inertness of CO₂. Ionic liquids represent an important class of catalysts for this process, however, there is lack of efficient strategy to screen the robust ionic liquids. Herein, 11 ionic liquids including three novel glutarimide-based ionic liquids are synthesized to catalyze the aforementioned reaction. Among them, [BZTMA][GLU] achieves a yield of 98.6% for quinazoline-2,4(1H,3H)-dione even under atmospheric pressure, with the following reaction conditions: 2-aminobenzonitrile (1 mmol), [BZTMA][GLU] (0.8 mmol), 70 °C, 8 h, and 1 mL of DMSO. Interestingly, the catalytic performance is related with the interaction of cation and anion and the amount of CO₂ absorption. Specifically, when the interaction between the anion and cation less than −6.35 kcal mol⁻¹, and the CO₂ absorption by the ionic liquid exceeds 1.37 mol CO₂ per mol IL, the catalytic yield will be greater than 98.6%. This relationship facilitates the efficient screening of new ionic liquids. The actual catalytic species is [BZTMA][GLU] and the –NH₂ group is activated, which is verified by combination of ¹H NMR spectra, Fourier transform infrared spectroscopy (FT-IR), and density functional theory (DFT) calculations. This work firstly reports the new strategy to screen the robust ionic liquid for the title reaction, which is favorable to the efficient identification of high-performance ionic liquids.