关键词: 离子液体, 模拟, 挥发性有机物, 吸收, 密度泛函理论

Abstract:

In order to expand and explore the potential applications and mechanism analysis of ionic liquids in the field of volatile organic compounds (VOCs) absorption, diethyl ether, acetone and dichloromethane were used as representatives of VOCs, through the quantum chemistry calculation module DMol3 in Materials Studio software, at the DNP/GGA/PW91 level. VOCs absorption sites of single-molecule and multi-molecule, hydrogen bonds, absorption energies (E_abs) and charge of three quaternary phosphine ionic liquids (PILs) were simulated and calculated, namely tributyl(propyl)phosphonium tetrafluoroborate ([P₄₄₄₃][BF₄]), tributyl(propyl)phosphonium bis(trifluoromethyl-sulfonyl)imide ([P₄₄₄₃][Tf₂N]), tributyl(propyl)phosphonium tetrafluoroacetate ([P₄₄₄₃][CF₃COO]). Accompanied by charge transfer, hydrogen bonds are formed between PILs and three types of VOCs. The dominant role of PILs in absorbing different types of VOCs is different. In the process of absorbing VOCs, anions and cations have different effects on the absorption. The results shown that the anions of PILs have little effect on the absorption of ether and acetone. The hydrogen bonds formed by the anions of PILs and α-H of ether are weak. The absorption sites of PILs for acetone are mainly the cation α-H or β-H and carbonyl O, and anions play a major role in the absorption of methylene chloride. The main role of PILs and methylene chloride is the hydrogen bond formed by the basic active site of the anion and the H of methylene chloride. The E_abs of [CF₃COO]^- for methylene chloride are obviously prominent. [P₄₄₄₃]⁺ ion pairs generally have three similar absorption active sites, and the space for accommodating VOCs molecules is mainly provided by cations. According to the analysis of the double ion pair spatial structure of PILs shows that the absorption sites of [P₄₄₄₃]⁺-based ILs having larger cations and smaller ion symmetry are not easily covered by hydrogen bonds. Among them, PILs composed of weakly alkaline and larger anions are more easily exposes its absorption sites. Experimental studies further show that compared with imidazole ionic liquids, PILs exhibit excellent VOCs absorption capabilities.

Key words: ionic liquids, simulation, volatile organic compounds, absorption, density functional theory