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为探究溶剂对合成有机金属框架化合物的影响机制,采用实验和DFT理论计算相结合的方法,研究溶剂N,N-二甲基甲酰胺(DMF)和N-甲基-2-吡咯烷酮(NMP)对溶剂热法合成有机金属框架材料[Zn4O(BDC)3]8的影响及溶剂与框架间的微观作用机制。粉末X射线衍射(XRD)和扫描电镜(SEM)结果表明,NMP在[Zn4O(BDC)3]8孔道中的吸附力较DMF的弱,NMP分子更容易从框架中脱除;热重(TG)和热重-红外联用(TGA/FT-IR)结果表明,以DMF为溶剂合成的[Zn4O(BDC)3]8的热分解温度和热稳定性较高;氮气等温吸附实验(BET)发现,以NMP为溶剂合成的[Zn4O(BDC)3]8的气体吸附性能更强,兰缪尔比表面积高于用DMF合成的[Zn4O(BDC)3]8。调控介电常数设定溶剂分别为NMP和DMF,用COSMO溶剂化方法对溶剂分子与框架化合物基本结构单元Zn4O(BDC)3间相互作用模型进行几何优化计算,发现溶剂设定为NMP时Zn4O(BDC)3优化结构的总能量较溶剂设定为DMF时的高8.6405 k J/mol,这说明DMF分子与Zn4O(BDC)3间的结合力强于NMP分子的,溶剂化作用降低了Zn与O间的离子性;用DMol3在GGA-BLYP/DN水平计算了DMF、NMP或DEF溶剂分子在[Zn4O(BDC)3]8晶体孔道中的相互作用,与DMF相比,NMP在孔道中能量状态稳定性较差,在能量状态角度上NMP应最容易从框架材料孔道中脱除。研究结果说明NMP更有利于合成性质良好的[Zn4O(BDC)3]8,与DMF相比NMP与框架结构基元间的作用力较弱。
In order to explore the mechanism of the effect of solvents on the synthesis of organometallic framework compounds, the solvent N, N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) Effect of Solvothermal Synthesis of Organometallic Framework Material [Zn4O (BDC) 3] 8 and Mechanism of Microcosmic Action between Solvent and Framework. The results of powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the adsorption capacity of NMP in [Zn4O (BDC) 3] 8 channels is weaker than that of DMF and the NMP molecules are more easily removed from the framework. ) And TGA / FT-IR showed that the thermal decomposition temperature and thermal stability of [Zn4O (BDC) 3] 8 synthesized with DMF were higher than those of the other samples. The nitrogen adsorption isotherm (BET) It was found that [Zn4O (BDC) 3] 8 synthesized with NMP was more gas-adsorptive and had a higher Langmuir surface area than [Zn4O (BDC) 3] 8 synthesized with DMF. The control dielectric constant was set as NMP and DMF respectively. The COSMO solvation method was used to optimize the interaction model between solvent molecules and Zn4O (BDC) 3, the basic structural unit of the framework compound. The results showed that when the solvent was set to NMP, BDC) 3 has a higher total energy of 8.6405 kJ / mol than that of DMF when the solvent is set to DMF, indicating that the binding between DMF molecules and Zn4O (BDC) 3 is stronger than that of NMP molecules. Solvation reduces Zn and O; the interaction of DMF, NMP or DEF solvent molecules in the channel of [Zn4O (BDC) 3] 8 was calculated at the level of GGA-BLYP / DN with DMol3. Compared with DMF, the energy of NMP in the channel State stability is poor, NMP should be most easily removed from the channel of the framework material in the energy state. The results show that NMP is more conducive to the synthesis of good [Zn4O (BDC) 3] 8, compared with the DMF NMP and the weak interaction between the framework of structural motifs.