双金属异相催化剂Fe3O4@La-MOF-Schiff-Pd/Ni的制备及其催化Suzuki偶联反应

Preparation and Catalytic Performance in Suzuki Coupling Reaction of Bimetal Heterogeneous Catalyst (Fe3O4@La-MOF-Schiff-Pd/Ni)

摘要:

将Fe3O4纳米粒子负载到金属有机骨架La-MOF中，然后向其中引入Pd/Ni活性位点，制得含磁性纳米粒子的Pd/Ni双金属异相催化剂（Fe3O4@La-MOF-Schiff-Pd/Ni），并通过SEM、TEM、EDS、ICP、PXRD和XPS对其进行了表征。结果表明，Fe3O4纳米粒子被成功嵌入到了La-MOF中，经过后合成修饰后，Pd和Ni活性位点被均匀分散在MOF框架中。该催化剂在Suzuki偶联反应中表现出较高的催化活性，以碘苯(1.0 mmol)和苯硼酸(1.2 mmol)为反应物时，最佳催化反应条件为：以无水乙醇为溶剂、无水碳酸钾为碱、反应温度80℃、反应时间为6 h、催化剂用量8 mg，在此条件下联苯产率达95%。该催化剂可以通过外加磁铁进行分离回收，经过5次循环使用后仍然保持较高的催化活性，产物产率为82%。Suzuki偶联反应机理探究结果表明，Pd和Ni可能具有协同催化效应。底物拓展实验表明，Fe3O4@La-MOF-Schiff-Pd/Ni双金属催化剂对含不同取代基的芳基溴化物和碘化物具有较好的普适性。

Abstract:

Pd/Ni bimetal heterogeneous catalyst (Fe3O4@La-MOF-Schiff-Pd/Ni) containging magenic Fe3O4 nanoparticles was prepared by a post-synthesis modification method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrum (EDS), inductive coupled plasma optical emission spectroscope (ICP), powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscope (XPS). The results showed that Fe3O4 nanoparticles were successfully embedded in La-MOF. The active sites of Pd and Ni were uniformly dispersed in the La-MOF after the post-synthetic modification. The catalyst exhibited high catalytic activity in the Suzuki coupling reaction. When iodobenzene (1.0 mmol) and phenylboronic acid (1.2 mmol) were used as reactants, K2CO3 was used as base, anhydrous ethanol was used as solvent, the amount of catalyst used was 8 mg, the yield of biphenyl was 95% at a reaction temperature of 80℃and a reaction time of 6 h. The catalyst could be easily recovered by magnetic separation and maintain high catalytic activity (82%) after 5 cycles. The proposed mechanism for the Suzuki coupling reaction revealed that Pd and Ni had a synergistic effect on catalytic activity. Moreover, the as-synthesized bimetallic catalyst demonstrated a common applicability to aryl bromides and iodides containing different substituents.