Chelation-activated multiple-site reversible chemical absorption of ammonia in ionic liquids

Developing new and facile strategies for multiple-site reversible chemical absorption of pollutant gases is of wide interests in chemical engineering research. Herein, a series of lithium (Li)-triethylene glycol (TEG)-chelated ionic liquids (ILs) with crown-ether-like cation and different anions were designed. The Li-TEG-chelated ILs were prepared in quantitative yields by simply mixing equimolar TEG and Li salts. It is found that the chelation of TEG with Li+ activates the hydroxyl sites in TEG for strong interaction with ammonia (NH3). Thus, the hydroxyl sites chelated with Li+, as well as the chelation-unsaturated Li+, provide the multiple sites for chemical absorption of NH3 in Li-TEG-chelated ILs. Moreover, the absorption of NH3 in Li-TEG-chelated ILs is totally reversible, with the NH3 solubilities remaining unchanged after eight times of recycling. The results obtained herein can provide useful guidance for the construction of gas absorbents with high capacity and excellent reversibility.