Developing NH 3 separation technology with high efficiency is very meaningful for the advancement of the NH 3 synthesis process. In this work, a new class of deep eutectic solvents (DESs) were designed by pairing N,N,N′,N′-tetramethyl-1,3-propanediamine dihydrochloride ([TMPDA]Cl 2 ) with phenol (PhOH) at the molar ratios of 1:3∼7. [TMPDA]Cl 2 + PhOH DESs have multiple weak-acidic groups and viscosities of as low as 48.1 cP at 298.2 K. They also exhibit excellent performance for the separation of NH 3 , showing not only efficient and selective but also reversible absorption of NH 3 . Especially, the solubilities of NH 3 in [TMPDA]Cl 2 + PhOH DESs at low pressures can reach 4.49 mol/kg of NH 3 at 298.2 K and 13.3 kPa, being superior to those of most of the DESs and ILs reported in the literature. The mechanism of NH 3 absorption was further elucidated by quantum chemistry calculations and 1 H NMR spectra. It is validated that the efficient absorption of NH 3 in DESs origins from the strong interaction of multiple weak-acidic groups of DESs with NH 3 .
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 crownether-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 (NH 3 ). Thus, the hydroxyl sites chelated with Li + , as well as the chelation-unsaturated Li + , provide the multiple sites for chemical absorption of NH 3 in Li-TEG-chelated ILs. Moreover, the absorption of NH 3 in Li-TEGchelated ILs is totally reversible, with the NH 3 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.
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