Studies On Synthesis And Hydrogen Adsorption Properties Of Al-based Metal Organic Frameworks

Nowadays,it is significant to develop clean and sustainable energy.Hydrogen,which is characterized by abundant resources,clean and pollution-free,is regarded as an ideal energy source consequently,hydrogen can be served as the most promising alternative energy.However,hydrogen energy has not been commercialized so far,the fundamental constraints is the problem of hydrogen storage,therefore,the development of materials with good hydrogen storage properties is the focus of the study.Metal-organic frameworks(MOFs)are new porous nanometer materials.MOFs have characteristics of high porosity,large specific surface area,low density,high crystallinity,and uniform pore size.Therefore it is widely used in gas storage.Al-based MOFs material not only has high thermal stability,but also has good chemical stability.In this paper,molecular simulation and experimental methods were used to study the application of MOF-519 and MOF-520 materials in gas adsorption.Firstly,the calculation model was established and hydrogen storage properties of the two kinds of materials in room temperature and 77 K were studied by grand canonical Monte Carlo(GCMC)method.In addition,the position of hydrogen in Al-based MOFs materials and adsorption configuration were also studied,so as to understand the influence factors of hydrogen storage performance better.By comparison,we found that the hydrogen storage performance of MOF-519 is better under cryosorption and vacuum pressure,then we synthesized MOF-519 materials by solvothermal method,activated by vacuum drying and supercritical CO2 drying method,the crystalline structure and morphology were analyzed by X-ray diffraction,adsorption instrument,SEM etc.It is found that compared with the vacuum drying method,the material obtained by the supercritical CO2 drying method has higher crystallinity,larger surface area.The adsorption properties of the material in the pressure range of 0-8kPa were obtained by measuring the hydrogen adsorption properties of the material at cryosorption,the obtained data can verify the reliability of the simulation method.In order to further improve the performance of hydrogen adsorption materials,we have researched the modification of materials,the effects of metal Li doping and introducing functional groups on the hydrogen storage properties of materials were studied by the molecular simulation method.The results indicate that hydrogen adsorption properties of the material can be greatly enhanced by two kinds of modified methods.Furthermore,the combination of experiment and simulation method is a effective approach to the screening of hydrogen storage materials.In the future,this method will play an increasingly important role in the development of new porous materials for gas storage.