Preparation Of Metal Organic Framework Materials MOF-74 And Their Adsorption Properties For Benzene And CO₂

Metal organic frameworks（Metal Organic Frameworks MOFs）are an important inorganic-organic hybrid material,and their applications include storage and separation of various mixed gases,catalysis,adsorbents,electrode materials,etc.Hundreds of MOFs have been synthesized so far,many of which have good performance in many aspects due to their good stability,large specific surface area,and large pore size.Therefore,the discussion of this issue is of great significance.MOF-74,also called CPO-27,is formed by the self-assembly of metal cations(M²⁺)(M=Zn²⁺,Mg²⁺,Co²⁺,Cd²⁺,Mn²⁺,Ni²⁺)and the organic ligand terephthalic acid.Three-dimensional honeycomb-like skeleton material.MOF-74 and its derivatives have a highly stable structure,and have been widely used in gas adsorption,molecular separation,electrochemistry,catalysis,drug delivery and other fields.The main work of this article is as follows:1.Solvothermal synthesis method is used,in which cobalt nitrate hexahydrate metal ion and 2,5-dihydroxyterephthalic acid are used as the solute of the reaction,and the mixed solution of DMF,methanol,and deionized water is the solvent.Among them,M²⁺:DHTA=3.3:1(M²⁺is a metal ion,representing Co²⁺).We prepared a series of Co-MOF-74 samples at three liquid-solid ratios of 35.48,47.31 and 70.97,three reaction temperatures of 90℃,100℃and 110℃,and two reaction temperatures of24h and 28h,and studied the reaction conditions.The effect of Co-MOF-74 on the adsorption of benzene and carbon dioxide was also studied on the effect of sample appearance and specific surface area.The following conclusions are drawn;the particles synthesized in the higher liquid-solid ratio are smaller than those synthesized in the lower liquid-solid ratio.Compared with the liquid-solid ratio and the reaction time,the reaction temperature has a greater influence on the sample preparation.At90℃,the samples prepared by us all have a larger specific surface area,which can reach 1116.79 m²/g.Using benzene and carbon dioxide as adsorbates,we also studied the adsorption performance of Co-MOF-74.It was found that the highest adsorption capacity of benzene can reach 209.59mg/g,and the highest adsorption capacity of carbon dioxide can reach 191.8473ml/g,which shows that the sample has good adsorption performance.The amount of adsorption is not only related to the specific surface area of the sample.The electrostatic force and magnetic force between the metal sites of the sample and the adsorbate molecules also have a large influence on the amount of adsorption.2.Solvothermal method is used,in which cobalt nitrate hexahydrate and ferrous chloride tetrahydrate provide metal ions and DHTA as the solute of the reaction,and the mixed solution of DMF,methanol and deionized water is the solvent.Among them,M²⁺:DHTA=3.3:1,M²⁺is a metal ion,representing Co²⁺and Fe²⁺),and CoFe-MOF-74 was successfully prepared under a series of different reaction temperatures and different starting material Co:Fe molar ratios.The effects of temperature and Co:Fe molar ratio on sample appearance and adsorption performance were explored,and the following conclusions were drawn;when the initial raw material Co:Fe molar ratio was equal to 3:1,under the conditions of reaction temperature of 110℃and 120℃The sample prepared by us has a high specific surface area,and the highest specific surface area can reach 469.63 m²/g.We studied CoFe-MOF-74’s adsorption performance for benzene and carbon dioxide,and compared it with Co-MOF-74.Under the condition of similar specific surface area,the highest adsorption capacity of CoFe-MOF-74 for benzene is 66.636 mg/g.The maximum adsorption capacity of CoFe-MOF-74 for carbon dioxide is 65.5053 ml/g,and the adsorption capacity for carbon dioxide is increased by 28.1%compared with that of Co-MOF-74.