| Covalent Organic Frameworks?COFs?are a series of novel crystalline porous polymers synthesized by organic structural units through condensation reaction.In 2005,Professor Yaghi's team first reported on this covalent organic framework formed by strong covalent bonding of organic light elements?such as B,C,O,N?with high specific surface area,adjustable porosity degree,precise periodicity and easy surface modification.Based on their unique properties,COFs have been studied extensively in the fields of gas adsorption and separation,catalysis,optoelectronics,proton conduction and drug transport,and have also caused researchers of related fields to pay close attention to such materials.According to the structure,COFs are mainly divided into two-dimensional?2D?COFs and three-dimensional?3D?COFs.Although the design and synthesis of two-dimensional COFs are relatively mature at present,most of them are one-dimensional single-channels in 2D COFs.In 2014,Prof.Zhao Xin's team proposed a two different kinds of pores in a COF for the first time,but until now,few reports on the design and synthesis of such materials have been reported because of the difficulties in synthesizing hierarchical pores COFs.Its structural units need precise angles to meet each other,and at the same time need to form a stable framework with periodic structure under the influence of covalent dynamic chemistry.This article mainly discusses the design and synthesis of a variety of new hierarchical pores COFs and combines with diatomite to form covalent organic framework composites containing microporosity-mesoporous-macroporous tertiary pores.The research of this topic is mainly divided into the following sections:In the first part,we elaborate the development history of COFs materials,the design principles,the types of reactions that have been synthesized,and the synthesis methods.It also briefly introduces the application of COFs in different fields according to the characteristics of COFs.At the same time,in order to cooperate with the third part of the experiment to synthesize multi-pores composites,this section also introduced the latest progress of multi-pores in this research direction and the introduction of the template agent-diatomite.In the second part,a multi-pores porous COF material with fluorine atoms was first synthesizedbysolvothermalmethodusing2,3,5,6-tetrafluoro-p-benzaldehydeand tetrakis?4-aminophenyl?ethene as precursors.We describe the design and synthesis of a new type of fluorine-containing double-hole 2D-COF,which is a hexagonal star-shaped structure linked by a D2hh symmetry monomer and a C2 symmetry monomer and named ETTA-TFA-COF.Has a 2.93nm hexagonal mesopores structure and a 1.43 nm triangle microporous structure.The structure of ETTA-TFA-COF was confirmed by theoretical simulation,PXRD characterization,nitrogen adsorption-desorption characterization and FT-IR spectroscopic analysis.At the same time,compared with similarly-structured but non-fluorine-containing COF materials,our synthesized ETTA-TFA-COF material exhibits very good stability in alkaline solutions.In the third part,a new two-dimensional multi-pores porous COFs material was synthesized using N,N,N”N”,N”-tetrakis?4-aminophenyl?-1,4-phenylenediamine which is a new structure unit for the first time,and it was compared with 2,5-Dimethoxybenzene-1,4-dicarboxaldehyde and terephthalaldehyde were synthesized by solvothermal condensation to form two different kinds pores in 2D-COFs materials,which were named TABA-DM-COF and TABA-PA-COF,respectively.In the same way,the structure of the two COFs was confirmed by theoretical simulation,PXRD characterization,nitrogen adsorption-desorption characterization and FT-IR spectroscopy.In addition,we also combined TABA-DM-COF with diatomite to synthesize a covalent organic framework composite containing microporosity-mesoporous-macroporous tertiary pores for the first time,and performed a series of characterization validations to make sure this composite was successfully prepared. |
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