The MOF~+ Technique Designing Molecules And Adsorption Research On Heavy Metal Ions U(Ⅵ) And Cr(Ⅵ)

Metal-organic Frameworks（MOFs）emerged as a novel porous material,which is more than popular due to its myriad self-assembly modules in molecule compared with other traditional porosint.As a result,it can enable different combination of functionalized structures.Many researchers have tried to apply MOFs materials in multifarious areas like gas storage,separation,catalyst,drug delivery and sensing.Additionally,another highlight characteristic in MOFs could be its massive atoms on the surface,but those atoms should be relatively stable to external environment,otherwise the stable structure cannot be processed.Barely correlative research have reported yet.Current functionalization methods facilitate its application in different circumstances through its own features,and it also available for designing molecules to make MOFs material more smoothly in application.It still have finiteness in exploring material functionalization of MOFs.This work have concluded that phenols can produce surface reaction with Fe²⁺and Fe³⁺,then the so-called MOF⁺methodology was established.This methodology was built on the basis of surface reaction with MOFs and iron ions,which can exhibit great performance in reduction-adsorption of heavy metal ions by the synergistic effect with MOFs and ferrous sulfate.Based on the ideas above,this thesis carried out the following work:using Zn as the metal center,2,5-dihydroxyterephthalic acid as organic ligands.Two isomers of MOFs materials were synthesized by hydrothermal method in different conditions,which called Zn-MOF-74 and UTSA-74 respectively.The purity of synthetic crystal was investigated by X-ray powder diffraction（PXRD）.It is found that the material can facilitate oxidation of ferrous ion to trivalent iron by Zn-MOF-74 chromogenic reaction and iron ion concentration tracking test.In order to explore the reaction mechanism,batch characterizations such as scanning electron microscopy（SEM）,energy dispersive spectrum（EDS）,X-ray photoelectron spectroscopy（XPS）and powder X-ray diffraction（PXRD）and transmission electron microscopy（TEM）for Zn-MOF-74 were conducted after the reaction.As a result,the so-called MOF⁺methodology,that is,reduction and co-precipitation by synergistic effect between MOFs and ferrous sulfate was established.On this basis,the properties of two MOFs materials for removal of uranium（VI）and chromium（VI）in solution are explored.Varies characterizations on materials after adsorption are also carried out.After integrating the obtained data,we can clarified adsorption models and adsorption mechanisms of Zn-MOF-74 and UTSA-74 on uranium（VI）and chromium（VI）adsorption by MOF⁺methodology.Currently,the treatment of heavy metal wastewater,such as uranium and chromium,is always suffering from low efficiency,high consumption and secondary pollution.The MOF⁺processing method adopted in this paper can solve these defects and problems well,which could provide new ideas and methods for MOFs materials on heavy metal wastewater treatment.