Highly Efficient Absorption of NO by Amine-Based Functional Deep Eutectic Solvents

To explore new reversible and environmentally friendly solvents for the capture of nitric oxide (NO), a series of amine-based functional deep eutectic solvents (DESs) were designed via ammonium salts (triethylenetetramine chloride-[TETA]Cl and tetraethylenepentamine chloride-[TEPA]Cl) and polyhydric alcohols (ethylene glycol-EG, 1,3-propanediol-PG, glycerol-Gy, and polyethylene glycol 2000-PEG). All of the DESs prepared showed good absorption capacities for 10 vol % NO. EG-[TEPA]Cl DES ( n EG / n [TEPA]Cl = 3:1) had the highest absorption capacity of 10 vol % NO, 0.327 g NO per g DES at 30 °C. Moreover, the EG-[TEPA]Cl DES ( n EG / n [TEPA]Cl = 3:1) showed excellent reusability for at least 5 recycles. The comparison of FT-IR and UV–vis spectra of DESs before and after NO absorption was made to study the absorption mechanism. The results indicated that the absorption of NO by the DESs was mainly a chemical process. One mole of amine group in HBA could react with two moles of NO to produce R 1 R 2 N–(NO)–NO, where both R 1 and R 2 belong to alkyl groups. This efficient and reusable absorption of NO in the functional DESs was expected to provide a new idea for the capture of NO.