2.1 Materials
CO2 (99.99 mol%) was purchased from Nanjing Chuangda Gas Co., Ltd, China. Tetraethylammonium hydroxide ([N2222][OH], 25 wt% in methanol), Tetramethylammonium hydroxide ([N1111][OH], 25 wt% in methanol), malononitrile (CH2(CN)2, 99 wt%), and methanol (99.5 wt%) were supplied from Aladdin Chemical Reagent Co., Ltd. Ethylene glycol, (EG, 99 wt%), imidazole (Im, 99 wt%), 1-Ethylimidazole (Eim, 99 wt%), dimethyl2-(2-aminoethoxy)ethanol (DMEE, 99wt%), Tetramethylene sulfone (SUL, 99 wt%),were purchased from Shanghai Macklin Biochemical Co., Ltd. All the chemicals were used directly without further purification.