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-molecules, hydrogen bonds, absorption energies (E_abs) and charge of three quaternary phosphine ionic liquids (PILs) were simulated and calculated, which are tributyl(propyl)phosphonium tetrafluoroborate ([P₄₄₄₃][BF₄]), tributyl(propyl)phosphonium bis(trifluoromethyl-sulfonyl)imide ([P₄₄₄₃][Tf₂N]), and 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 showed 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. Analysis of the double ion pair spatial structure of ionic liquids shows that PILs composed of weakly basic and larger anions are more likely to expose their 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

摘要：

为拓展和探究离子液体在挥发性有机物（VOCs）吸收领域的潜在应用和机理，以乙醚、丙酮和二氯甲烷为VOCs代表，模拟计算了三种季类离子液体（PILs），即三丁基（丙基）季四氟硼酸盐（[P₄₄₄₃][BF₄]）、三丁基（丙基）季双三氟甲基磺酰亚胺盐（[P₄₄₄₃][Tf₂N]）、三丁基（丙基）季三氟乙酸盐（[P₄₄₄₃][CF₃COO]）吸收单分子和多分子VOCs的活性位点、氢键、吸收能（E_abs）、电荷等。研究表明，PILs与三种VOCs之间均形成了氢键并伴随电荷转移，阴离子对乙醚和丙酮吸收的影响不显著；阴离子对二氯甲烷的吸收则起主要作用，[CF₃COO]^-的E_abs值明显较大。[P₄₄₄₃]⁺类离子对一般具有3个类似的吸收活性位点，其容纳VOCs分子的空间主要由阳离子提供。离子液体的双离子对空间结构分析表明，由碱性弱且体积较大阴离子组成的PILs更容易暴露其吸收位点。实验研究进一步表明，相比咪唑类离子液体，PILs表现出优异的VOCs吸收能力。

关键词: 离子液体, 模拟, 挥发性有机物, 吸收, 密度泛函理论