Design, Assembly And Separation Properties Of Three Dimensional Salen-based Covalent Organic Frameworks

As a burgeoning class of porous lightweight crystalline organic materials,covalent organic frameworks?COFs?were endowed with various traits such as prominent chemical stability,permanent porosity and uniformly distributed pore channel.Therefore,they have been widely used in storage and separation of molecules,heterogeneous catalysis,sensors,optoelectronics and energy storage as the multifunctional mediums.In this dissertation,four crystalline Salen-based COFs were synthesized.The structures of these Salen-based COFs were well characterized and studied including Powder X-ray diffraction,FT-IR spectra,N₂ adsorption experiment and so on.Subsequently,their application properties of separating ethylbenzene,styrene and xylene isomers were thoroughly explored.This dissertation includes three chapters as follows:In chapter 1,the research background was briefly introduced including the development of covalent organic frameworks?COFs?,commonly reaction bond types used in constructing COFs and their applications in the fields of storage and separation of molecules,heterogeneous catalysis and energy storage.Then,the opportunities and challenges were briefly discussed.Finally,the significance and research progress of this thesis were overviewed.In chapter 2,two kinds of salicylaldehyde monomers were synthesized,and then,four 3D Salen-based COFs were constructed by self-assembled with ethylenediamine in the presence or in the absence of zinc acetate under solvothermal conditions.The crystal structure of the four COFs was simulated based on the experimental PXRD data,the accordance of the simulated values and the experimental values confirmed that the correctness of the structure.Then various characterization methods were texted,they shown high specific surface area,permanent porosity and excellent chemical stability.Finally,the four COFs were used as the stationary phase in the HPLC to evaluate their properties in separating ethylbenzene,styrene and xylene isomers,and achieved the baseline separation of them for the first time using COFs.The separation gave comparable or comparatively better selectivity and resolution than other materials used in separation.In chapter 3,a briefly summary and prospect of the work in this dissertation were given.