Indra Sandipa, Subramanian Ranga, Daschakraborty Snehasis
Department of Chemistry, Indian Institute of Technology Patna, Bihar 801106, India.
J Phys Chem B. 2022 May 26;126(20):3705-3716. doi: 10.1021/acs.jpcb.2c00076. Epub 2022 May 11.
Unrestricted emission of volatile organic compounds (VOCs)─a threat to human health and the environment─can be controlled to a large extent by the capturing mechanism. Few recent experimental studies explored the efficacy of the deep eutectic solvent (DES), a designer solvent with some fascinating properties, as a VOC-capturing medium. Through the partition coefficient measurement, it was found that the choline chloride-based DESs exhibit excellent VOC-capturing potencies. However, a molecular picture of the above absorption process is still lacking. Here, we study the molecular mechanism of the absorption of two commonly occurring VOCs, toluene and acetaldehyde, in two different choline chloride-based DESs with varying donor molecules, urea, and levulinic acid via the molecular dynamics simulation technique. Strong absorption of the VOCs is observed in both the DESs. The free energy profile for the absorption process has been explored using the umbrella sampling method. The VOCs are preferentially solvated near the liquid/vapor interface. The simulated partition coefficients for the VOCs from the vapor to the liquid phase show good agreement with the experimental results. Detailed analyses of the spatial and orientational structure of the VOCs and different components of DESs are performed to elucidate the interaction among them. The above analyses have indicated that DES is a better VOC-capturing medium compared to a room-temperature ionic liquid, which is more extensively studied in the literature.
挥发性有机化合物（VOCs）的无节制排放对人类健康和环境构成威胁，而通过捕获机制可在很大程度上对其进行控制。最近很少有实验研究探索深共熔溶剂（DES）作为VOC捕获介质的效果，DES是一种具有一些迷人特性的定制溶剂。通过分配系数测量发现，基于氯化胆碱的DES表现出优异的VOC捕获能力。然而，上述吸收过程的分子层面情况仍不明确。在此，我们通过分子动力学模拟技术研究了两种常见VOC（甲苯和乙醛）在两种不同的、含有不同给体分子（尿素和乙酰丙酸）的基于氯化胆碱的DES中的吸收分子机制。在这两种DES中均观察到对VOC的强烈吸收。使用伞形采样方法探索了吸收过程的自由能分布。VOC优先在液/气界面附近被溶剂化。VOC从气相到液相的模拟分配系数与实验结果吻合良好。对VOC的空间和取向结构以及DES的不同成分进行了详细分析，以阐明它们之间的相互作用。上述分析表明，与文献中研究更为广泛的室温离子液体相比，DES是一种更好的VOC捕获介质。
