Design,Synthesis And Adsorption Properties Of Covalent Triazine-based Frameworks

With the progress of industry and the development of science and technology,the environmental problems,such as water pollution,air pollution and nuclear pollution,have become more and more serious,and the related technical research is urgent.Adsorption is a low energy consumption and simple operation method to remove pollutants in the environment.Covalent Triazine-Based Frameworks(CTFs)are porous organic polymers containing triazine rings,which are composed of covalent bonds connecting light elements such as C,H,O,and N.CTFs have the advantages of good chemical and hydrothermal stability,high specific surface area,as well as structural and functional diversity.In this work,two covalent triazine-based frameworks with different pore sizes were designed and synthesized for different types of adsorption targets such as iodine vapor adsorption,organic pollutant adsorption and carbon dioxide gas adsorption separation,and their performances of adsorption and separation were explored.The main contents are as follows:(1)In this work,a three-dimensional mesoporous CTF was designed and synthesized for the adsorption of radioactive iodine.Methyl functional groups were introduced into the planar monomers to make their benzene rings perpendicular to each other to obtain a new stereo monomer CTTD,which was polymerized at high temperature to form mesoporous CTF(CTF-CTTD)with three-dimensional structure.The CTF-CTTD has a specific surface area of 1684 m2 g-1 and a pore volume of 1.44 cm3 g-1,and a multi-scale porous structure of micropores and mesopores.Due to triazine ring,?-? conjugated structure and the multi-scale pore structure with large pore volume,it is used to capture iodine vapor in this work.The results show that CTF-CTTD can capture iodine vapor effectively and has the highest adsorption capacity of iodine(387%),exceeding most of the porous organic frameworks reported.Moreover,its good stability makes CTF-CTTD a good regeneration performance.(2)Furthermore,the CTF-CTTD was applied to the removal of organic pollutants in wastewater.The removal of rhodamine B(RhB)from wastewater by adsorption was studied as an example.The results show that CTF-CTTD can effectively remove RhB,and the maximum adsorption capacity is 667 mg g-1.For low concentration RhB solution,the adsorption removal rate can reach above 99.9%.Moreover,CTF-CTTD has a good regeneration performance.Therefore,CTF-CTTD has promising application prospects for the adsorption of organic pollutants.(3)Finally,a two-dimensional ultrafine porous CTF with high heteroatom content(N and S)was designed and synthesized for the separation of small molecule gases.CTF-BTD was applied to the adsorption and separation of CO2 and N2 or CH4 mixtures because of its ultrafine pore structure and high content of heteroatoms.The experimental results show that CTF-BTD exibit good separation performance for the mixture of CO2 and N2 or CH4.The separation selectivity coefficients of CTF-BTD for CO2/CH4 and CO2/N2 are 13.0 and 64.4 at 298 K and 1 bar,respectively.Moreover,the good stability makes CTF-BTD a good carbon dioxide cycle adsorption performance.