Study Of Low Temperature Recrystallization Synthesis Schiff Base Porous Polymer

Schiff base polymers(COPs)are covalent organic materials connected by imine bonds,which have many advantages such as high stability,rich function and controllable structure.The 2D/3D polymers hold great promise for catalysts,sensors,molecular sieves,ion transport,etc.In recent years,the synthesis of COPs has been the focus of research.Therefore,low-temperature recrystallization method,a new and universal synthesis method,was proposed to simplify the synthesis method of Schiff base products and accelerate the reaction rate of Schiff base.A series of COPs with different structures were successfully prepared and the reaction rate of Schiff base was accelerated by adjusting the freezing concentration effect induced by low temperature recrystallization without catalyst and external energy injection.In this thesis,based on low temperature recrystallization method,a series of COPs with different structures were synthesized by Schiff base reaction.The structure of COPs is analyzed through various characterization,and the effects of annealing temperature and initial monomer concentration on the reaction rate were also discussed.Using rich amine COPs as photocatalyst,the relationship between its structure and catalytic degradation of methyl orange was discussed.The main content of this thesis is summarized as follows:(1)Schiff base reaction was carried out with aniline and p-benzaldehyde as a small molecular model.The low temperature recrystallization method was proved to accelerate the Schiff base reaction by NMR,FT-IR and UV-Vis.Combined with the characterization results of the Schiff base polymer,it is proved that the rate of Schiff base reaction can be accelerated by low-temperature recrystallization without catalyst and external energy injection.Increasing the annealing temperature and the initial monomer concentration enhanced the freeze concentration effect,which accelerated the Schiff base reaction rate,that is,the yield increased;On the contrary,the reaction rate of Schiff base slows down and the product yield decreases.(2)Firstly,we explored the effect of temperature on the structure of the polymer,successfully maintained the interaction between polyvinyl alcohol and polythiophene molecules by low-temperature drying.Then the influence of temperature and other factors on the structure of Schiff base polymers are further discussed.By reducing the annealing temperature or initial monomer concentration in the low-temperature recrystallization process and shortening the reaction time,the rate of Schiff base reaction is slowed down,the number of unreacted functional groups in the product is increased,and the defect content in Schiff base polymers are increased.(3)The amorphous nitrogen rich COPs were used as catalyst for photocatalytic degradation of methyl orange under visible light irradiation.Compared with crystalline products,the catalytic rate of amorphous products is twice that of crystalline products.It is speculated that the high catalytic activity is due to the defect vacancies in amorphous materials.After changing the initial monomer concentration,nitrogen rich COPs with different vacancy content were obtained.When the vacancy content was too high,the catalytic rate decreased.