The Preparation And Modification Of MOF UiO-66 For Hydrogen Storage

At present,coal,oil,natural gas and other fossil energy is still in the dominant position of the world energy structure.However,the use of fossil energy is limited,such as limited total amount and non-renewable.Consequently,energy reserves are decreasing and environmental pollution is becoming more and more serious.Hydrogen energy,as a renewable and clean energy,is a sustainable development solution.But the utilization of hydrogen energy is faced with such problems as high cost,durability,poor operability,difficult to storage and the safety,which restrict the wide use of hydrogen energy.In recent years,physical adsorption has been used to absorb hydrogen rapidly because of its safety,reliability,high storage efficiency and easy to adsorb/desorb quickly hydrogen under mild conditions.And UiO-66,a kind of micro-porous metal-organic framework,has good physical adsorption properties.Firstly,the optimum synthesis conditions of UiO-66 were investigated,and the hydrogen adsorption capacity under different conditions at 77K and 0-100KPa was studied.A series of studies show that when the metal source is ZrCl₄,Zr⁴⁺/H₂BDC=1:2 with 47.4mL solvent and2.6mL acetic acid regulator,and when the crystallization temperature is 150?,crystallization time is 21h,vacuum activation temperature is 150?,the synthesized UiO-66 has the highest diffraction peak intensity and the best morphology,at the same time,the highest hydrogen storage capacity at 77K and 0-100KPa.Then,taking UiO-66 under the optimum synthesis conditions as the research object,doping other organic ligands to modify was studied.Two organic ligands doped with1,3,5-benzenetricarboxylic acid and 2-aminoterephthalic acid were mainly investigated.It was discovered that,UiO-66 which has good crystal shape and morphology could not be synthesized by adding 1,3,5-benzenetricarboxylic acid in organic ligand.When UiO-66 was modified with 2-aminoterephthalic acid,the result showed that the optimum doping ratio could improve the crystallinity,morphology and hydrogen adsorption.It is concluded that the hydrogen adsorption capacity of UiO-66 at 77K and 0-100KPa can be increased by adding appropriate amount of 2-aminoterephthalic acid.Among them,adding 40%2-aminoterephthalic acid into the organic ligand has the best hydrogen adsorption capacity at77K and 0-100KPa.So the modification was the most successful.Finally,taking UiO-66 under the optimum synthesis conditions as the research object,doping other metal ions to modify was studied.The results show that both Cu-UiO-66 and Zn-UiO-66 with better crystalline can be synthesized by doping appropriate amount of trandition metal ions.The amount of hydrogen adsorbed by UiO-66 in the range of 77K and0-100KPa can be increased by proper doping of Cu²⁺or Zn²⁺,and the thermal stability can also be well maintained.By comparison,30Cu-UiO-66 and 6Zn-UiO-66 were the optimum metal doping materials,what's more,the modification effect of Cu²⁺was better.