Efficient absorption of low pressure NH3 by non-ionic phenol-based deep eutectic solvents with multiple acidic sites

In chemical industry, efficient absorption of ammonia (NH3) from industrial exhaust remains a challenge and significant issue for resource utilization and pollution control. Present study proposed a new strategy to design non-ionic deep eutectic solvents (DESs) using phenolic analogues. Several phenol-based DESs with multiple acidic sites were constructed by paring catechol (Cat) or resorcinol (Res) with phenol (PhOH) and investigated as feasible NH3 absorbents from physical property, NH3 absorption performance, and mechanism analysis. Among the as-obtained DESs, Res/PhOH (1:3) demonstrated attractive NH3 absorption capacity at 303.15 K (11.862 mol/kg at 101.3 kPa, and 6.391 mol/kg at 5.0 kPa), surpassing most DESs and ionic liquids (ILs) reported in the literatures. Meanwhile, it displayed good reversibility, satisfactory thermal stability, and high NH3/CO2 selectivity. The mechanism of NH3 absorption was further elucidated using FTIR and NMR spectra, and Quantum chemistry calculation, and inferred as the strong and multiple interaction between NH3 and weakly acidic sites of DESs.