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 (nEG/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 (nEG/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 R1R2N–(NO)–NO, where both R1 and R2 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.