Studies On Design And Synthesis Of Multifunctional Carbazole Based Porous Organic Frameworks And Their Adsorption And Separation Properties

As an important branch of solid materials,porous organic materials are a kind of multifunctional polymer materials with nanometer-scale pores.Due to their high specific surface area,fixed porosity and high pore volume and adjusting the configuration by different linkages and chemical bonds,making them suitable for multiple fields,such as semiconductor materials,photochemistry and sensing,and energy storage,adsorption/separation and catalysis.Porous organic materials shine particularly in the direction of energy purification,gas adsorption and separationPorous Organic Frameworks(POFs)and covalent organic frameworks(COFs)are connected by covalent bonds.The difference between them is that COFs are usually crystalline polymers.Therefore,due to the structural characteristics of the two materials and the rich choice of building monomers,they have attracted scientific researchers'widespread attention in recent years.Compared with traditional inorganic porous materials and inorganic-organic composite porous materials,POFs/COFs can obtain higher specific surface area and larger pore size by choosing different reaction methods and multiple monomers and linkers.Benefiting from the strong interaction of covalent bonds,POFs has the characteristics of low density,high thermal stability and chemical stability.Based on the above research,this paper has carried out a series of research work on the design and synthesis of POFs/COFs materials with microporous/mesoporous structures and their applications in energy purification,selective adsorption/separation of organic gases.The research results include the following three aspects1.Porous Organic frameworks with polycarbazole groups for efficient separation of aromatic sulfides in liquid hydrocarbon fuels.Because of their structural characteristics,POFs materials have shown great potential in absorbing and separating organic impurities and pollutants.Therefore,after the research and analysis of previous work,we have prepared a series of organic backbone structures with unique functional groups:o-Cz-POF,m-Cz-POF and p-Cz-POF,and applied them in desulfurization for liquid hydrocarbon fuels.The vapor equilibrium adsorption test illustrates the extremely high adsorption capacity of Cz-POFs for aromatic sulfides(3-methylthiophene).The instantaneous adsorption rate test and IAST theoretical simulation calculations prove that 3-methylthiophene is preferred adsorbing on Cz-POFs.Fixed-bed experiments show that Cz-POFs can effectively selectively absorb sulfides and obtain hydrocarbon fuels with a sulfide content of nearly 0 ppm.The high stability and desulfurization efficiency of Cz-POFs make them a promising new type of porous adsorbent for deep and efficient desulfurization2.Restraining linkage rotation to build 3D rigid quasi-crystalline Covalent Organic Frameworks for effectively adsorbing and separating organic pollutants Covalent Organic Frameworks(COFs)are the representatives of reticular crystalline porous materials,and their structures can be divided into 2D meshes and 3D meshes by precise structural design using chemical reactions of different organic building blocks.At present the main challenge of designing COFs is to obtain crystallized structure.Through the research and exploration of molecular structure,using the idea of inhibiting the linkage rotation between the building units,in this paper,for the first time,a[8+2]irreversible C-C coupling reaction was used to demonstrate the synthesis of a 3D-COF with a microporous structure.(Named p4CzTN).The choice of 8 active sites carbazole-based building monomers with a quasi-cubic structure and a restricted molecular configuration is critical to the construction of crystalline 3D-COFs,as other carbazole-bearing monomers with 8 active sites are also synthesized for comparison The two amorphous POFs and the crystalline p4CzTPN were applied to the adsorption and separation of harmful gases such as benzene/cyclohexane,SO2/CO2,and CS2/CO2.Experiments showed that all three porous materials possessed good separation properties and they can be potential organic pollutant separators3.Expand the design of new POFs materials and explore their properties based on the selection of functional monomers and theoretical methods of skeleton design According to the selection of functionalized monomers,the theoretical methods of skeleton design were used to expand the synthesis of new POFs and explored their properties.Based on the previous work,we summarized the experience of successful synthesis on functional POFs materials.On the one hand,two POFs with specific functional groups were developed and synthesized:p3CzBN and p5CzBN,and applied to CS2 adsorption experiments based on their pore characteristics.On the other hand,according to the guidance of topological structure theory,a series of POFs with microporous-mesoporous structures were synthesized through the coupling reaction by selecting specific building units and linkers,named pC10-Ph,pPh-Ph and pEthy-Ph.The obtained materials were used for the adsorption and separation of ethylene and ethane.The experimental results showed that p3CzBN and p5CzBN have a very high adsorption capacity for CS2,and has surpassed the p4Cz materials in the previous work.The adsorption levels of pC10-Ph,pPh-Ph and pEthy-Ph for ethylene and ethane are among the best in porous organic materials.Moreover,because of their highly conjugated framework structure,they possess certain potential in the field of photoelectricity such as charge transport.