Fabrication Of MOFs-based Functional Bulk Materials And Their Removal Performance And Mechanism For Pollutants In Water

With the rapid development of economy and society,water pollution and shortages have become one of greatest challenges in China and the world.Removal of pollutants from aqueous solution with high efficiency is therefore crucial for supplying safe drinking water and recycling of wastewater.Recently,environmental nanotechnology based on nanomaterials for the efficient removal pollutants from water shows a promising efficiency.Metal-organic frameworks（MOFs）,a new type of crystalline hybrid porous material,have invoked significant global research interest due to their excellent performance in water pollution remediation.However,the intrinsic powder characteristics of MOFs are deemed problematic in various stages,and their potential toxicity to environmental exposure also largely limits their practical applications.Especially for the heterogeneous process,the ultrafine powder will cause the bed lamination drop and clogging within pipes,which must be avoided in engineering application.To address the challenges of MOFs materials in engineering application,this thesis presents the in-depth investigation on the fabrication of MOFs-based functional bulk materials and further exploring the removal performance and mechanism of pollutants in water.The main research contents and conclusions are as follows:（1）Mixed-electrospinning method for constructing ZIF-67 fibrous film:Based on the essential factors（composition and structure）for catalysts,ZIF-67 nanocrystals with excellent catalytic performance were screened and prepared,and followed by mixing with polypropylene（PAN）to obtain an electrospinning precursor.Then,ZIF-67/PAN nanofibers were obtained by electrospinning technique.The ZIF-67/PAN nanofibers demonstrate a film with good flexibility and processing in the macroscopic.This film exhibits high performance in the activation of persulfate for degradation of organic pollutants such as bisphenol A（BPA）,tetracycline（TC）and acid yellow-17（AY-17）.This strategy successfully overcomes the separation problems of MOFs powder catalysts after the reaction.（2）Electrospinning-in situ growth strategy for fabrication of MOFs fibrous films:First,the precursor Zn²⁺(Co²⁺)ion was mixed with PAN,and Zn²⁺/PAN or Co²⁺/PAN film was obtained by electrospinning;Secondly,the obtained Zn²⁺/PAN or Co²⁺/PAN film was immersed in the 2-methyl imidazole solution.The in-situ-ZIF-8/PAN or in-situ-ZIF-67/PAN fibrous film was formed by in situ growth.The in-situ-ZIF-8/PAN film demonstrates high adsorption capacity of U（VI）(530.3 mg g^-1 at p H=3.0).The XAFS and XPS investigations reveal that the high adsorption is ascribed to the complexation between U（VI）and 2-Me IM.In situ-ZIF-67/PAN also shows good performance in the activation of persulfate to degrade organic pollutants,which is superior to ZIF-67/PAN in the reaction kinetics.（3）Electrospinning-pyrolysis method for preparation of hollow carbon nanofiber films（HCNFs）:ZIF-8 nanoparticles were first mixed with PAN solution,and then the mixture solution was electrospun to fabricate composite nanofibers（denoted as ZIF-8/PAN）.After pyrolysis,HCNFs were successfully obtained due to ZIF-8 nanoparticles are converted into hollow structures during the pyrolysis.The HCNFs demonstrate a good flexibility and electrical conductivity,and excellent performance in the activation of persulfate for catalytic degradation of tetracycline,and does not cause secondary pollution.Radical quenching experiments,EPR,and electrochemistry investigation confirm that non-radical（electron transfer intermediates）dictates the TC degradation in the use of HCNFs.（4）Freeze-drying-pyrolysis for construction of hierarchical porous carbon aerogels（CAs）:First,the prepared ZIF-8 powder was mixed with an aqueous solution of agarose（AG）,subsequently subjected to freeze-drying to form ZIF-8/AG aerogel;The resulting ZIF-8/AG aerogel was finally carbonized into ZIF-8/AG-CAs under N₂ atmosphere.The ZIF-8/AG-CAs display a low density of 24 mg cm^-3,a high specific surface area of 516 m² g^-1,and a large pore volume of 0.58 cm^-3 g^-1.Furthermore,the CAs exhibit 3D porous structure and show high performance for adsorption of the organic solvents such as n-hexane,dichloromethane,petroleum ether,etc.,indicating the great potential application in repairing oil spills.Through the understanding of the above scientific issues,this thesis establishes the new concepts and methods to construct MOFs-based functional bulk materials for environmental practical applications,and provides key supporting materials for the engineering applications of environmental nanotechnology.