Application Oriented Design And Synthesis Of Ionic Covalent Organic Framework Materials And Composites

With the increase of the social population and the development of society,the global demand for energy is rapidly expanding.In addition,carbon dioxide exhausted from industry and creatures are also causing huge problems for human society.To solve these problems,humans need clean fuels like hydrogen and methane to achieve a sustainable future.In this regard,the potential applications of porous organic materials in gas absorption and storage,catalysis,and electrochemistry are expected to meet the needs of sustainable energy.Porous materials are thought to have very high specific surface areas,functionality,and tunable pore structures.The many advantages of porous materials have attracted great interest from material scientists.Covalent organic frameworks（COFs）are crystalline porous polymeric materials in which organic building blocks are linked by strong covalent bonds.The synthesis process of this kind of material is thermodynamically controlled and the crystallinity is formed in dynamic covalent chemical mechanisms.However,the material structures will influence the properties of the material,and ionic COFs is a typical example.In this work,we describe the design methods,synthesis and functionalization methods,pore engineering and final rational application of COFs systematically.The paper mainly consists of three parts as follows.In Chapter 2,we introduce the application of three-dimensional ion-type covalent organic framework materials in fast,recyclable,and selective ion exchange.The authors selected a novel three-node and two self-contained chain link ligands to successfully synthesize two novel three-dimensional ion-type covalent organic framework materials（3D-ICOF-1 and 3D-ICOF-2）.The materials have high specific surface area.Experiments have proved these two kind of materials are able to be applied in fast,recyclable,and selective ion exchange and they are superior than most commercial ion exchange materials.The results also suggest that this type of material has great potential for movement of radioactive ions in nuclear contamination.Not only that,the materials are able to capture greenhouse gas CO₂ effectively,which is thought to lead to global warming.More interestingly,during analysing the structure,we found that the interpenetration of the material changed from a nine-fold interpenetration,similar to COF-320,to a triple interpenetration due to the self-contained ions of the link molecule.In Chapter 3,we report a non-interpenetrating,mesoporous,covalent organic framework material with a pts topology.In the previous COFs material research,most researchers focused on two-dimensional materials.And in the research on 3D COFs,researchers tend to focus on simple dia topology.In this article,the large-scale nodes and smaller chain-link molecules were selected to synthesize non-penetrating pts topology COF material（3D-pts-COF-1）.It is the non-interlacing phenomenon that causes the material to have the largest three-dimensional COFs pores to date,and the data shows that the pore size can reach up to 3.5 nm.Later,the authors prepared a COF material（3D-pts-COF-2）with double interpenetration.By comparing the experiment results,we found that this kind of COF with non-interlaced structure has advantages over the interspersed structure in many aspects such as energy storage.The authors have successfully assembled larger ionic polymers using the advantages of large pores.It is an example for size selective catalysis by ion exchange of ionized polymers in the channels.In Chapter 4,we synthesized a novel three-dimensional fluorine-containing covalent organic framework material,JUC-515,using room temperature ionic liquid method.Compared with solvothermal method,this method has the advantages of low reaction temperature and pressure,short reaction time,simple operation,no catalyst and no organic vapor pollution,so it is expected to be able to carry out large-scale preparation of COFs.JUC-515 has high crystallinity,high specific surface area and abundant pore structure,and has good selective adsorption capacity for carbon dioxide.It is expected to be applied to selective separation of carbon dioxide.In summary,this study aims to explore and understand the relationship between structure and property in covalent organic framework materials,and to realize control material properties by structure design.We designed and synthesized a variety of novel COFs materials,and explored their application in selective ion exchange,CO₂capture,ionic polymer assembly,selective gas adsorption and separation.At the same time,we also understood the phenomenon of interspersing and strategies to reduce or terminate the interspersed phenomenon.We hope our work will guide the future synthesis of COFs materials,and ultimately contribute to the better production and life of mankind.