Preparation Of Mg-MOF-74and Computational Study Of CO₂Adsorption

Metal organic frameworks are a kind of porous materials that popularizedthese years with their advantages that perform better than conventional porousmaterials. Such as high chemical and thermal stability, regular and ordered pores,structure and pores are tunable due to user’s request. And due to their highspecific surface area and porosity, they are ideal materials for gas storage andadsorption. In order to test the result of our simulation work, we have comparedthem with the experimental result. Then, we can introduce this simulationtechnique into prediction work and provide some reliable data for our furtherresearch on MOFsAt first, hydro thermal method is introduced to synthesis a kind of highthermal stability, simple structure, regular pores Mg-MOF-74crystal. And wehave investigated almost all the factors that may affect the synthesis, such as thetemperature, time, solvent, post synthesis treatment etc. We symbolize the Mg-MOF-74crystal by powder X-ray diffraction (PXRD), thermal gravimetricanalysis (TG), scanning electron microscopy (SEM). Results of our experimentshows that use hydro thermal synthesis making Mg-MOF-74crystals, when themolar ratio of Mg(NO3)6H2O and DHTA is3.34:1, synthesis procedure last for24hours, volume ratio of DMF/ethanol/H2O is15:1:1, and keep the synthesistemperature at125℃, we can produce Mg-MOF-74crystals with high crystallize,perfect structure and surface.Using software of Material Studio6.0and Sorption simulate the gasadsorption performance in Mg-MOF-74. Firstly, build the molecular model ofMg-MOF-74, CO2and N2respectively. Assign the force field type and charge toevery molecular of the whole system. Then optimize the crystal model of Mg-MOF-74with the Forcite module in MS. In order to compare the effect of forcefield type for adsorption, we complete the simulation task with Material Studio,simulating the CO2and CO2/N2in Mg-MOF-74in Universal and COMPASSforce field respectively. Then we do the same job with Sorption procedure.Moreover, we investigate the effect of temperature, namely278/298/318etc. Wehave found that CO2adsorption quantity is higher in low temperature than that inrelative higher temperature. And the energy of the adsorption has the same trend as the adsorption quantity. As the N2molecular being introduced into thisadsorption system, the adsorption of CO2has become easier.