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]CI 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 degrees C. Moreover, the EG-[TEPA]Cl DES (nEG/n([TERA]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 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.