Designed Synthesis And Structural Characterization Of 3D Imine–Linked Covalent Organic Frameworks Based On Tetraldehyde Ligand

Covalent organic frameworks(COFs)are an emerging class of porous crystalline polymers with broad potential applications,such as gas adsorption and separation,catalysis,optoelectronics,chemical sensing,drug delivery and clean energy applications and so on.In comparison with these crystalline porous solids,the COFs materials possess the advantages of low density,large surface area,tunable pore size and structure,facilely-tailored functionality,and so on.The rapid development in this area has,therefore,attracted extensive interest from scientific researchers.However,while the design and synthesis of 2D COFs is already well established,the design and synthesis of 3D COFs have been still considered a challenge.Thus,the exploration of new 3D COFs is of paramount importance for the development of 3D COFs materials and diversifying their properties.These are discussed in detail in the first chapter of this article.In addition,the classification,design principles,synthesis methods and its applications in different fields of COFs materials are also discussed in the first chapter.In chapter 2,a new crystalline imine-linked covalent organic frameworks,TA-COF-1,was synthesized by condensation of tetra-(4-formylphenyl)methane and p-Phenylenediamine under solvothermal conditions for the first time.The crystal structure of TA-COF-1 was charactered by PXRD,SEM,IR and TGA et.al.It is indicated that TA-COF-1 has good thermal stability,high Langmuir surface area(1771.19 m2 g-1),small pore size(1.28 nm)and big pore volume(0.753 cm3 g-1).In addition,TA-COF-1 shows uptake as high as 61.78 cm3 g-1 of H2.It worth to mention that this is the first time that a tetrahedral structure of aldehyde ligands was used to succesfully synthesis 3D crystalline imine-linked COFs.In chapter 3,another new crystalline imine-linked covalent organic frameworks,TA-COF-2,was synthesized by condensation of tetra-(4-formylphenyl)methane and tetra-(4-anilyl)methane under solvothermal conditions for the first time.S imilarly,the crystal structure of TA-COF-2 was charactered by PXRD,SEM,IR and TGA et.al.It is indicated that TA-COF-2 has good thermal stability and chemical stability,high Langmuir surface area(1313.91 m2 g-1),small pore size(0.73 nm)and big pore volume(0.474 cm3 g-1).In addition,TA-COF-2 shows uptake as high as 106.02 cm3 g-1 of H2,43.64 cm3 g-1 of CO2.It worth to mention this is the first time that two tetrahedral structure of aldehyde/ amino ligands were used to succesfully synthesis 3D crystal ine imine-linked COFs.In chapter 4,learning from the synthesis method of traditional hierarchically zeolite molecular sieve,we select diatomite as the base of hierarchically porous COFs.Through in site synthetic strategies,the diatomite/covalent organic framework composites were successfully prepared with hierarc hically porous structure(Dt-EA/ TA-COF-2).The composite Dt-EA/TA-COF-2,due to the introduction of macroporous diatomaceous earth,overcomes the single-stage microporous disadvantage of TA-COF-2 itself,which is also possible for the potential application of the composite material,Moreover,this strategy for the synthesis of multi-stage pore COFs materials based on diatomaceous earth also provides valuable reference value for subsequent related synthesis work.