Zn-MOF-74负载ILs的结构稳定性和吸附研究

离子液体（ILs）作为一种新型绿色溶剂应用广泛，以多孔材料MOFs作为支撑体负载ILs，不仅有望降低离子液体的高粘性，而且有助于提高材料的吸附分离能力，但要如何选择适合MOFs体系来负载ILs是一个难点。本文采用密度泛函理论（DFT），利用VASP和Gaussian 09 程序对负载IL（[Emim][BF4]）的Zn-MOF-74的结构稳定性进行系统研究，从几何结构、电荷分析、相互作用等方面将Zn-MOF-74@[Emim][BF4]复合体系与[Emim][BF4]和Zn-MOF-74比较分析。计算结果表明，负载[Emim][BF4]的Zn-MOF-74体系中，IL的阴离子与Zn-MOF-74的开放金属位点Zn发生强相互作用， Zn、F1原子之间因库仑力成键，造成了MOF-74配位构型的改变。IL的负载扰乱了Zn-MOF-74结构的对称性，增强了离子间相互作用。Zn-MOF-74 @[Emim][BF4]复合体系形变过程伴随着电荷转移，其吸附能为-1.032 eV，绘制的差分电荷以及相互作用图验证MOF和IL之间发生了化学吸附。进一步探讨负载离子液体的Zn-MOF-74吸附能力，研究了CO2在复合体系中吸附作用机制。

Probing the Structural Stability and Adsorption Property of Zn-MOF-74 Supported Ionic Liquids

Ionic liquids (ILs) are widely used as a new green solvent. Taking porous material MOFs as supports in ILs can prospectively reduce the high viscosity of ILs and contribute to improve the adsorption and separation capacity of material. However, how to choose the appropriate MOFs systems to support ILs is a difficult point. In this research, the structure stability of Zn-MOF-74 which supports ionic liquid [Emim][BF4] has been studied by VASP and Gaussian 09 packages. Comparing Zn-MOF-74@[Emim][BF4] materials with pure [Emim][BF4] and pure Zn-MOF-74, a thorough research has been explored from geometric structure, Bader charges, electron density difference and interactions diagrams. Results showed that Zn-MOF-74 is structurally unstable compared with before when [Emim][BF4] is present in the crystal structure. The strong interaction generates between the Zn atom and [BF4]? anion of [Emim][BF4], and the Zn and F1 are bonded by Coulomb forces caused the change of MOF coordination configuration. The loading of IL disrupts the symmetry of Zn-MOF-74 structure and enhances the interionic interactions. After deformation, the charge transfers between Zn-MOF-74 and [Emim][BF4] and the adsorption energy is -1.032 eV. The chemical adsorption between MOF and IL is verified by the electron density difference analyze and the electron interaction. In order to investigate the adsorption capacity of Zn-MOF-74@[Emim][BF4] composites, the mechanism was studied for CO2 adsorption.