Synthesis, Characterization And Catalytic Properties Of Amino-Functionalized Materials

The Knoevenagel condensation and the Henry reaction are important C-C bond forming reactions that have been extensively studied and also applied in industrial processes. The reaction products α,β-unsaturated olefins are often used as important imtermediates in organic synthesis. Bases as catalysts are often applied in the Knoevenagel condensation and the Henry reaction, in which, primary, secondary and tertiary amines are used as homogeneous catalysts. However, the homogeneous catalysts are difficultly separated from their reaction media and hardly recycled. Apparently, development of reusable catalysts for the Knoevenagel condensation and the Henry reaction is desirably required.In the current study, two different amino-functionalized catalysts, the so-called NH2-SBA-15and NH2-MIL-101(Al) are prepared. The mesoporous silica SBA-15has ordered pore channels and a controllable pore size distribution. Owing to their high surface areas, tunable pore, and functionality, MOFs have a variety of potential applications, mainly in catalysis. These two types of heterogeneous catalysts are used in the Knoevenagel condensation and the Henry reaction. The main results are summarized as follows:1) Amino-funetionalized SBA-15catalysts were synthesized by a one-pot strategy. The obtained catalysts were characterized by XRD, N2adsorption, and FT-IR techniques as well as by elemental analysis. The catalytic activity and reusability of NH2-SBA-15were evaluated in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, in which water was used as solvent. NH2-SBA-15with the optimized amino loading shows an excellent performance in terms of activity and recyclability in the Knoevenagel condensation reaction. In addition, the optimized NH2-SBA-15catalyst was used in the Henry reaction of benzaldehyde and nitromethane, and the results show that the NH2-SBA-15catalyst has a good performance.2) Compared to those in NH2-MIL-101(Cr) synthesized by a post-grafting method, the amino groups in NH2-MIL-101(Al) synthesized by a one-step strategy should be more stable. The catalytic activity and reusability of NH2-MIL-101(Al) were evaluated in the Henry reaction of benzaldehyde and nitromethane. The results show that NH2-MIL-101(Al) showes a better recyclability in the Henry reaction but a lower activity, compared to NH2-MIL-101(Cr). NH2-MIL-101(Al) was also used in in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, in which water was used as solvent, and the results show that the framework of the used catalyst is collapsed. However, when ethanol is used as solvent, NH2-MIL-101(Al) is stable but its catalytic activity is rather low..