Study Of The Pore Modification And In-situ Composites Based On COFs

Covalent Organic Frameworks?COFs?are a type of new materials with regular network structure composed of C,N,H and other light elements.Network structure of porous material.This kind of material has been widely concerned in many fields because of its good structural characteristics.In recent years,COFs has become a hot topic in scientific research.COFs usually have multiple types such as imine type and borate type,and the building units usually have multiple functionalities such as two,three,and four.Therefore,COFs have structural diversity and strong designability.Since the first report of COFs in 2005,there has been more in-depth research.From the beginning,the discovery of new topologies has gradually evolved into the synthesis of new functional building blocks.However,COFs and porous materials with similar structural characteristics compared with MOFs?Metal Organic Frameworks?,there is still a big gap in the structural diversity.So far,there have been relatively few studies on COFs composite materials.This is mainly due to the fact that this is a new class of materials and the requirements for the synthesis conditions of the materials are high.Therefore,in order to broaden the types of COFs,the preparation of composite materials may be the development direction of this type of materials at this stage.Composite materials refer to two or more materials with different properties synthesized into new materials through optimized methods through different synthesis methods or technical means.Generally,composite materials can not only maintain the properties of each component,but also often have properties not possessed by a single component through the interconnection effect of each component in the synthesis process.Based on the above considerations,the composite materials preparation of COFs are very meaningful for enhancing the physical and chemical properties of the materials and widening the application range of the materials.This article takes the composite materials of COFs as the starting point,focusing on the pore modification and application research of synthetic materials,and proposes two methods for the modification of pores after the synthesis of COFs and the synthesis of COFs in situ on carbon materials,and the bipyridine To construct the synthesis of monomer-derived COFs,the synthesis of pores and the application research for carbon dioxide adsorption,and the preparation and performance of polyimide-based COFs based on the in-situ generation of carbon materials.On the one hand,this article uses 5,5'-diamino-2,2'-bipyridin?Bpy?and trialdehyde pyrogallol?Tp?as raw materials to prepare Tp-Bpy COF.Then,the Tp-Bpy COF was modified with polyethyleneimine?PEI?to successfully synthesize PEI@Tp-Bpy COF composite PEI.Through characterization,it is found that the composite material has similar physical and chemical properties as COFs:well crystallinity,large specific surface area(1223 m²·g^-1-1703 m²·g^-1),and high stability.Based on the structural characteristics of the material,its application performance in carbon dioxide adsorption was studied.Under the conditions of 273 K and 1 bar,the carbon dioxide adsorption capacity of Tp-Bpy COF is 70.78 cm³·g^-1,and the carbon dioxide adsorption capacity of PEI@Tp-Bpy COF is 102.00 cm³·g^-1.Compared with Tp-Bpy COF,the amount of adsorption increases.44.11%.In addition,in the carbon dioxide cycle adsorption performance test,the PEI@Tp-Bpy COF has no significant loss of carbon dioxide adsorption capacity after 5 cycles,and compared with Tp-Bpy COF in the industrial exhaust gas model has a higher carbon dioxide/nitrogen adsorption selectivity.On the other hand,this paper uses pyromellitic anhydride?PMDA?,tris?4-aminophenyl?amine?TAPA?and two kinds of nano-carbon materials:C₆₀ and carbon nanotubes?CNT?as raw materials,The in-situ synthesis of COFs is based on the preparation of polyimide covalent organic framework materials C₆₀@PMDA-TAPA COF and CNT@PMDA-TAPA COF generated in situ on the surface of carbon materials.SEM and TEM characterization showed us in the micro layer that C₆₀@PMDA-TAPA COF realized the mutual doping of COFs and nano carbon material C₆₀ micro layer,CNT@PMDA-TAPA COF realized the growth of COFs material on the surface of carbon nanotube.Other characterization results also show that PMDA-TAPA COF materials retain the characteristics of COFs while in-situ composite carbon materials,which makes it have more potential application prospects in fields such as photovoltaics and supercapacitors.In conclusion,the composites synthesized by the above two methods retain the structural advantages of COFs in terms of structure and properties.At the same time,the potential research value and application fields of the composites are widened through the strategy of pore modification,which provides a way for the synthesis of COFs composites by pore modification.