Synthesis,Structure And Properties Of Photochromic Covalent Organic Framework

Covalent organic frameworks(COFs)are a new type of porous materials,which are constructed by covalent bonds of organic structural units.The COFs with precise network structure obtained by covalent bonding of organic building units have the characteristics of high crystallinity,uniform pore size,low density,large specific surface area,high stability and adjustable structure,etc.,which are very attractive for gas storage and separation,drug delivery,catalysis,energy conversion,etc.COFs materials,which are composed of functional organic structural units,also have unique optical,photoelectric and other characteristics.Through post modification and other means,COFs materials can also be combined with other functional functional groups or organic molecules to realize the extensive application of COFs in other aspects.Photochromic organic molecules have always been the research focus of scientists.They are widely used in photoelectric devices,data storage,information recording and processing,fluorescent molecular switches and other aspects.In this thesis,the photochromic spiropyran and diarylethene derivatives are combined with COFs to obtain a new type of photochromic COFs,and their structures,properties and applications are further explored.Ⅰ.By solvothermal method,a new fluorescent COF material with-C≡C-H functional group was synthesized from 2,6-bis(2-propynyloxy)naphthalene-1,5-dicarbaldehyde and 1,3,5-tris(4-aminophenyl)benzene,and characterized by polycrystalline x-ray diffraction,infrared spectroscopy,transmission electron microscope,thermogravimetry,nitrogen adsorption and desorption analysis,fluorescence,etc.A photochromic COF material with spiropyran molecule was obtained by modifying the photochromic spiropyran molecule to COF via click reaction.Under the irradiation of UV and visible light,the spiropyran molecules in this COF material can still realize the open-loop and closed-loop reversible conversion,and with the reversible change of color.The reversibility of photoisomerization,the fatigue resistance of solid and solvent,and the influence of p H value were studied.The application of fluorescence-based p H sensing technology in edible vinegar was also preliminary studied.Ⅱ.Based on the COF-x reported in the literature,a series of COFs frameworks with-C≡C-H were synthetised.Through click reaction,azido cyclopentene thiophene was modified on the COFs,and then a series of photochromic porous materials were obtained,and a closed-loop reaction with color change would take place under the irradiation of 365 nm ultraviolet lamp.The polycrystalline x-ray diffraction,infrared spectroscopy,transmission electron microscope,thermogravimetry,nitrogen adsorption and desorption analysis,fluorescence of the modified COFs were studied.In this thesis,we show that the photochromic molecules can be combined with COFs by click reaction,and then the photochromic COFs can be obtained.It provides a new idea for the application research of COFs.