Highly Efficient Nitric Oxide Absorption by Environmentally Friendly Deep Eutectic Solvents Based on 1,3-Dimethylthiourea

In this work, a series of 1,3-dimethylthiourea (1,3-DMTU)-derived environmentally friendly deep eutectic solvents (DESs) were reported and used for nitric oxide (NO) capture. The DESs were synthesized by mixing 1,3-DMTU with different hydrogen bond donors at different molar ratios, and their NO absorption performances were investigated. All of the DESs possessed excellent NO absorption performance. Notably, the absorption capacity of 1,3-DMTU/P4444Cl (3:1, molar ratio) DES is 4.25 mol/mol. 1,3-DMTU had a paramount effect on the performance of DESs, and the NO absorption capacity of these DESs increased with the increase of the molar ratio of 1,3-DMTU/P4444Cl in DESs. Moreover, the 1,3-DMTU-derived DESs showed good reusability; they could be recovered and reused 5 times. Through a combination of experimental results, quantum chemical calculation, proton nuclear magnetic resonance, and Fourier transform infrared spectroscopy investigation, the absorption mechanism was proposed and the easy deprotonation of 1,3-DMTU in DES was demonstrated to promote the bonding of NO.