Synthese Of Metal-Organic Frameworks Catalysts And Their Catalytic Performance

MOFs have a lot of advantages relative to other porous materials, such as metal unsaturated ligand, large surface area, they are widely used in catalysts, gas adsorption, separation, storage areas and molecular sensor. MOFs have great prospects as heterogeneous catalysts. Especially, the magnetic carrier are encapsulated in MOFs to obtain magnetic MOFs@SiO2@Fe3O4. This kind of catalytic material is not only easier to separate and recycle based on the external magnetic fields, and its unique core-shell configurations extend the surface area of the catalytic material, the contact area between the catalyst and the reactants, so it has received the widespread attention in the field of heterogeneous catalysis. There are a variety of MOFs, and the classic representative of MOFs is MILs.In this paper, MIL-53(Al) was synthesized by solvothermal method. Meanwhile, Fe3O4 was also synthesized by solvothermal method, and then the SiO2 shell was coated on its surface by hydrolysis. Finally, magnetic MIL-53(Al)@SiO2@Fe3O4 materials were prepared by coating different contents of MIL-53(Al) on the surface of SiO2@Fe3O4 magnetic carrier (15.5%MIL-53(Al)@SiO2@Fe3O4,27.3%MIL-53(Al)@SiO2@Fe3O4,38.8% MIL-53(Al)@SiO2@Fe3O4,49.9%MIL-53(Al)@SiO2@Fe3O4). The structure of samples was characterized by XRD, FT-IR, XRD、FI-IR、BET、SEM、 TEM. The catalytic performances of two catalysts (MIL-53(A1), MIL-53(Al)@SiO2@Fe3O4) were evaluated for Friedel-Crafts acylation reaction between different substrates. And the effects of different conditions on the reaction were all studied. The results are shown as follows:The catalyst synthesized was pure MIL-53(Al). In this reaction, when the reaction temperature was 25 ℃, the amount of catalyst MIL-53(Al) was 1: 0.06 (n1:ncataiyst), indole 4 mmol, benzoyl chloride 12 mmol, and the dichloromethane was used as solvent, the catalytic performance of MIL-53(Al) was the best, the conversion of indole achieved 97.1%, the selectivity of 3-acylindole came to 81.1% and the yield of 3-acylindole was 93.9% after 8 h. It could be reused without a significant degradation in catalytic activity after five successive runs.The synthesized catalytic material MIL-53(Al)@SiO2@Fe3O4 catalyst showed a greater specific surface area and superparamagnetic. Compared with the pure MIL-53(Al) catalyst, it exhibited better performance on the recovery and reuse, while maintained its high catalytic activity for Friedel-Crafts reaction. In the reaction, when the amount of MIL-53(Al)@SiO2@Fe3O4 catalyst was 1:0.037 (n1:ncataiyst), indole 4 mmol, benzoyl chloride 12 mmol, methylene chloride was solvent at room temperature for 8 h, the conversion of indole was 98.3%, the selectivity of 3-acetylindole was 81.1%. And MIL-53(Al)@SiO2@Fe3O4 still exhibited good catalytic activity after reused five times. With respect to pure MIL-53(Al), it has better catalytic activity in the conversion of reaction, selectivity and the yield.The synthesized 38.8%MIL-53(Al)@SiO2@Fe3O4 catalyst maintained its high catalytic activity for Friedel-Crafts alkylation of toluene and benzyl chloride. In the reaction, when the amount of MIL-53(Al)@SiO2@Fe3O4 catalyst was 1:0.030 (n1:nCataiyst), at 55 ℃ for 6 h, the conversion of toluene was 96.8%, the selectivity of p-isomer was 60.9%, the yield of reaction was 95.9%. After reused five times, the conversion of toluene was 92.1%, the selectivity and yield of p-isomer was 60.4%,88.1%.