Construction Of Benzimidazole Functionalized Covalent Organic Frameworks For Heterogeneous Catalysis

Covalent Organic Frameworks(COFs) are a new type of crystalline porous organic materials, which are constructed with purely organic building blocks through strong covalent bonds. Because of their low density, high stability and large surface area, and diverse functions, COFs have showed great applications in gas storage, optoelectronics, and catalysis. However, most of the reported COFs have focused on the construction of new structures. On the contrary, a limited number of functionalized COFs have been reported so far. This thesis mainly focuses on the design, synthesis, characterization and application of benzimidazole functionalized COFs.(1) Two imine-linked benzimidazole functionalized COFs (COF-LZU30 and COF-LZU31) were successfully synthesized. The prepared COF-LZU30 and COF-LZU31 possessed well-defined and predictable two-dimensional pore structures. Moreover, COF-LZU30 and COF-LZU31 showed excellent catalytic activity in the Knoevenagel reactions. In particular, COF-LZU31 showed higher activity than homogeneous system in the aprotic solvents, which may be attributed to the uniform distribution of the catalytic active sites in COF-LZU31.(2) Based on COF-LZU30 and COF-LZU31, we attempted to synthesize benzimidazolium functionalized COFs via the "post-synthesis" and "bottom-up" strategies.In addition, we explored how the "post-synthesis" strategy influenced the stability of COF-LZU30. Meanwhile, we have tried to synthesize the metal-carbene functionalized COFs.