Study On Preparation Of Metal Organic Matrix Compound MOF-5 From Different Zinc Sources And Adsorption Properties Of Benzene Series

Because of the pollution of production and life,benzene series can be widely detected in human living and living environment,and has strong harm to human blood,nerve and reproductive system.In the developed countries,the concentration of benzene series in the atmosphere has been regarded as one of the contents of routine monitoring of atmospheric environment,and strict indoor and outdoor air quality standards have been stipulated.Of all the methods used to treat benzene contamination,physical adsorption is ideal.Because of its high specific surface and high porosity MOF-5 organometallic skeleton compounds have some advantages in the adsorption of benzene series,so they have been obtained in gas adsorption and separation,gas storage and so on continuous development.The main work of this thesis is as follows:1.Pure phase was prepared by solvothermal method with zinc nitrate hexahydrate as the metal center,terephthalic acid as the organic ligand and dimethylformamide as MOF-5 organic solvent.By regulating the molar ratio of metal ions to organic ligands,crystallization temperature and crystallization time,the factors affecting the synthesis of MOF-5 materials are studied.From XRD analysis,the synthesized MOF-5 materials are easily hydrolyzed.From nitrogen adsorption analysis,when Zn²⁺:BDC^-=2?ZB=2?,the specific surface area of the crystallized 7h samples is relatively good.Among them,crystallization 150?the sample ratio table Maximum area,1038.89 m²/g.When ZB=3/4,the optimum crystallization conditions are140?crystallization 9h.The crystallization 5h the sample is easily attacked by water molecules.In the sample crystallization 7 and 9 h,the crystallization temperature rises from 140?to 160?.the specific surface area of the sample decreases gradually,and the temperature change between140 and 150?has a great influence on the adsorption performance of the sample,and the crystallization 140?is relatively good.additionally,at the same crystallization temperature,the crystallized 9 h sample has a higher specific surface area.Compare 3 different the sample with the best adsorption performance in the molar ratio.ZB=3,the specific surface area of the sample is the largest.The results show that the optimum Zn²⁺and BDC^-molar ratio of synthetic MOF-5materials are between 2³.2.Pure phase was prepared by solvothermal method using zinc dihydrate and zinc hexahydrate as mixed zinc source as metal center,terephthalic acid as organic ligand and dimethylformamide as MOF-5 organic solvent.By changing the molar ratio of two zinc sources,crystallization temperature and crystallization time of the two zinc sources to study the influencing factors of synthetic MOF-5.From the XRD analysis,it can be seen that the XRD image of the sample conforms better with the standard peak,and there is no hydrolysis,that is,the MOF-5 phase prepared by using the double zinc source is more pure.Moreover,the XRD image shows that the diffraction peaks of 170?crystallized 10 h are low,which indicates that the crystallization time is too long at high temperature,which makes the skeleton of the sample collapse easily.We can see from the FT-IR image that the absorption peak of the crystallized 6h sample is stronger than that of the crystallized 8/10 h sample,the nitrogen adsorption analysis shows that the specific surface area 6 and 10h samples is higher than that 8h samples,this may be due to the MOF-5 structure formed by crystallization 6h,Zn?CH3COO?2·2H2O takes the lead in forming MOF-5 structure with H₂BDC,that is,the Zn²⁺in the sample is provided by Zn?CH3COO?2·2H2O;and crystallization 10h,Zn?NO3?2·6H2O provides a framework for Zn2+and H₂BDC construction;and the crystallization 8h,probably because the crystallization time is not enough for the Zn²⁺and H₂BDC provided by Zn?NO3?2·6H2O to form a stable framework,the crystallization time is too long relative to NOF-5 materials synthesized by Zn?CH3COO?2·2H2O.3.Some of the above samples were taken for the steam adsorption analysis of benzene series,and the adsorption capacity of benzene and toluene was analyzed.The vapor adsorption of benzene series showed that it was consistent with the law of nitrogen adsorption analysis,When the molar ratio of Zn²⁺to BDC^-is 2,the sample with better benzene adsorption performance can be obtained by crystallization about 7h;Under the same conditions,the adsorption capacity of 6and 10 h samples prepared two zinc sources is obviously better than that 8h samples.Among them,the benzene adsorption of the samples prepared using two zinc sources is relatively high in the two synthesis methods.