Salen-based Covalent Organic Frameworks: Designed Synthesis And Properties

The Salen unit represents one of most privileged ligands in coordination chemistry,which has been widely used as efficient catalysts for numerous organic ransformations.Covalent organic frameworks(COFs)are an emerging class of organic crystalline porous polymers,and have owned unique characteristic: crystalline structure,orderly channel,large π conjugate structure and so on.Introducing Salen into the skeleton of COF materials,it can not only realize the heterogenization of Salen ligands,but also give COF coordination properties and chiral functionality.This thesis focuses on the designed synthesis and properties of Salen-based COF materials,including the following aspects:We developed a kind “kill two birds with one stone” approach to construct a Salen-based covalent organic framework(COF),Salen-COF,in which both the construction of the COF structure and the functionalization with Salen moieties have been realized in a single step(Figure1).Due to its structural uniqueness,Salen-COF possesses high crystallinity and excellent stability.Based on this,a series of metallo-Salen-based COFs were prepared via metalation for possible applications.We further explored the catalytic activity of Co/Salen-COF in the Henry reaction.On this basis,we also attempted to synthesis of 3D-Salen-COFs using the same strategy.(?)In addition,we also use the “bottom up” strategy to realize the construction of chiral Salen-COFs,in which Salen unit is pre-designed building block.Especially the design and synthesis of chiral Salen-COF,LZU-Salen-9,which has unique helical morphology(Figure 2).Using opposite configuration of chiral precursor,the material with opposite helical direction can be obtained.We realized the precise control of the macroscopic morphology of COF materials from the molecular level,as well as the chiral transfer and amplification from the microscopic molecules to the macroscopic materials.Then,a series of control experiments were conducted to explore the regulation of helical morphology.Also,we have proposed the self-assembly mechanism of helical morphology.On this basis,we do some research on the universality of helical morphology phenomenon by constructing a series of chiral Salen-COFs,and we also found the similar phenomenon in LZU-Salen-5.(?)...