Izadyar Mohammad, Rezaeian Mojtaba, Victorov Alexey
Computational Chemistry Research Laboratory, Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
Department of Chemistry, St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg 199034, Russia.
Phys Chem Chem Phys. 2020 Sep 16;22(35):20050-20060. doi: 10.1039/d0cp03612a.
In this article, 20 ns molecular dynamic (MD) simulations and density functional theory (DFT) were used to investigate the absorption of CO2 molecules by some functionalized 1,8-diazabicyclo[5,4,0]-udec-7-ene (DBU)-based ILs. According to the MD results, the highest coordination number for NC is observed in the case of [DBUH+][Im-], which indicates that the functionalization of the imidazole anion by different alkyl groups decreases the interaction ability of the anion with CO2 molecules. The addition of water molecules to the ILs decreases the ability of the anion to interact with CO2 because of the hydrogen bond formation between the imidazole anions and water. Two different paths were proposed for CO2 absorption by the ILs, and the effect of alkyl groups on the kinetics and thermodynamics of the reaction was analyzed by using the M06-2X functional at the 6-311++G(d,p) level of theory in the gas phase and water. On the basis of the results, CO2 absorption is more favorable in [DBUH+][Im-], thermodynamically. Kinetic parameters show that the alkylation of the imidazole anion by ethyl, propyl, iso-propyl, and phenyl groups decreases the rate of CO2 absorption, because of the steric and electron-withdrawing effect of different alkyl groups. In the presence of water molecules, the lowest activation Gibbs energy is related to [DBUH+][Im-], which confirms the greater ability of this IL in CO2 absorption.
在本文中，采用20 ns分子动力学（MD）模拟和密度泛函理论（DFT）研究了一些功能化的基于1,8 - 二氮杂双环[5,4,0] - 十一碳 - 7 - 烯（DBU）的离子液体对CO₂分子的吸收情况。根据MD结果，在[DBUH⁺][Im⁻]的情况下观察到NC的最高配位数，这表明咪唑阴离子被不同烷基功能化会降低阴离子与CO₂分子的相互作用能力。向离子液体中添加水分子会降低阴离子与CO₂相互作用的能力，这是因为咪唑阴离子与水之间形成了氢键。提出了两种不同的离子液体吸收CO₂的路径，并在气相和水中，使用理论水平为6 - 311++G(d,p)的M06 - 2X泛函分析了烷基对反应动力学和热力学的影响。基于这些结果，从热力学角度来看，[DBUH⁺][Im⁻]中CO₂的吸收更有利。动力学参数表明，咪唑阴离子被乙基、丙基、异丙基和苯基烷基化会降低CO₂的吸收速率，这是由于不同烷基的空间位阻和吸电子效应。在存在水分子的情况下，最低的活化吉布斯自由能与[DBUH⁺][Im⁻]相关，这证实了这种离子液体在吸收CO₂方面具有更强的能力。
