Mg-MOF-74在Knoevenagel缩合反应中的催化性能研究

Study on catalytic performance of Mg-MOF-74 in the Knoevenagel condensation reaction

在溶剂热条件下,使用四水合乙酸镁和2,5-二羟基对苯二甲酸合成Mg-MOF-74,通过元素分析、扫描电子显微镜(SEM)、X衍射衍射光谱(XRD)、红外光谱(FT-IR)和热重(TG)表征方法,分析和确定其结构和性质。碱土金属中心和酚酸氧配体的结合,极大地增强了金属有机骨架化合物(MOFs)材料的碱性。为了探索Mg-MOF-74的催化活性,将其用于催化苯甲醛与氰基乙酸乙酯的Knoevenagel缩合反应,生成(E)-α-氰基肉桂酸乙酯。通过改变反应时间、溶剂类型、底物浓度、催化剂的量、搅拌速率和反应温度等条件来提高转化率。在较温和的条件下,反应的转化率达到94.5%,选择性大于99.5%。催化剂易于从溶液中分离出来,表现出良好非均相性。在5次循环实验之后,催化效果没有明显的降低。

Under solvothermal conditions,Mg-MOF-74 was synthesized by magnesium acetate and 2,5-dihydroxyterephthalic acid.Through elemental analysis,scanning electron microscopy,X-ray diffraction spectroscopy,infrared spectroscopy and thermogravimetry,the structure and properties of them were analyzed and determined.The incorporation of alkaline earth metals and phenoxy structural ligand was an effective way to increase the basicity of MOFs.To explore catalytic activity of Mg-MOF-74,it was applied to catalyze the Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate to produce ethyl(E)-α-cyanocinnamate.The conversion rate could be improved by changing the reaction time,solvent type,substrate concentration,amount of catalyst,stirring rate and reaction temperature.Under milder conditions,the conversion rate of the reaction was 94.5% and the selectivity was greater than 99.5% for the Mg-MOF-74.The Mg-MOF-74 could be easily separated from the solution with good heterogeneity and it was used 5 runs without significant loss of catalytic efficiency.