Synthesis And Modification Of Mg-MOF-74 And Its CO₂/H₂O Adsorption Performance

Since the industrial revolution,CO2 emissions increased rapidly,resulting in global warming and a series of natural disasters.Therefore,how to reduce carbon emissions is becoming an increasing concern.Metal organic framework(MOF)is one of the largest CO2 adsorption capacity materials,which has a huge surface area ratio and high porosity.At present,there are still some insufficient like the lack of synthesis conditions,the study for the selection adsorption performance is not enough,the modified method is not perfect and so on.Therefore,the synthesis and the modification of Mg-MOF-74 and its properties of selection adsorption for CO2/H2O are reserched in this paper.First of all,Mg-MOF-74 is synthesized by solvent thermal synthesis from Mg(NO3)·6H2O and 2,5-dihydroxybenzene carboxylic acid.And optimize the synthesis conditions of the sample by studying the activation temperature,crystallization time,and the ratio of liquid to solid.The optimal synthesis conditions are obtained:the ratio of liquid to solid is 86.88,the crystallization time is 28h,the crystallization temperature is 125,the crystallization time is 28h,the activation temperature is 125,the activation time is 6h.Through the analysis of XRD,SEM,FTIR and TG of the best samples,the samples showed high purity,crystal structure,regular morphology,and thermal stability.Mg-MOF-74 adsorption capacity of CO2 at different temperatures is measured by thermogravimetric analyzer,the result show that the Mg-MOF-74 adsorption capacity are 4.78mmol/g,2.00mmol/g,1.26mmol/g respectively at normal pressure 0?,60? and 90?.Secondly,study on the single component adsorption for H2O and the two components adsorption for CO2/H2O of Mg-MOF-74 using the self-made penetration test device.The research shows that the adsorption capacity for H20 of Mg-MOF-74 is 19.6mmol/g on atmospheric pressure and 35? conditions.The CO2 capacity of Mg-MOF-74 is 2.84mmol/g and 2.27mmol/g respectively at the conditions of relative humidity of 12%and 19%.It's show that the Mg-MOF-74 has a strong adsorption capacity for H2O.At the same time,the increase of H20 concentration affected the adsorption of Mg-MOF-74 for CO2.Finally,Modified the Mg-MOF-74 by ammonia solution,the modification conditions are optimized by two factors:the concentration of ammonia solution and stirring time.The best optimum conditions are ammonia solution concentration is 6mol/L and stirring time is 24h.And the best samples are characterized and the thermal stability is analyzed.The results show that the crystal structure of the modified sample is complete,the morphology of the sample is slightly corroded,the functional groups are complete,the N element appears,and the thermal stability is strong.Through testing the adsorption properties for CO2 of Mg-MOF-74.The results showed that:at atmospheric pressure and 60 ? and 90 ? conditions respectively,the adsorption amounts of the new Mg-MOF-74 are respectively 2.58mmol/g and 1.48mmol/g,compared with modified,increasing by 29%and 17.5%.The results show that the modification effect of Mg-MOF-74 has achieved remarkable results,and the adsorption capacity for CO2 of Mg-MOF-74 is obviously improved.