Preparation Of MOF-808@PAN Nanofiber Composites And Study On The Properties Of Degradation Chemical Warfare Agent

Chemical warfare agent(CWAs)not only has mass destruction to human beings and animals,but also has the ability to seriously damage the environment.Up to now,public safety incidents caused by chemical warfare agents still occur from time to time,which seriously threaten the safety of human life,so it is still urgent to develop efficient and convenient protective materials.With the progress of material science,the protective and digestion materials of chemical warfare agents are constantly updated.A mong them,metal-organic frame material(MOFs)has strong reactivity to CWAs because of its adjustable structure and function,clear porous structure,large surface area and rich catalytic sites,which makes MOFs the best candidate material for adsorption and digestion of CWAs.However,the practicability of powdered MOFs is greatly limited because of its easy agglomeration,poor processability,difficult recovery and so on.MOFs is generally used in combination with the substrate.How to combine MOFs with substrate efficiently and stably,fully retain the degradation activity of MOFs,and improve the practicability of composites has always been the research focus of chemical warfare agent protective materials.In order to solve the above problems,from the point of view of improving practical value and expanding application,through electrospinning technology,PAN nanofibers were modified by dopamine materials to prepare high-strength and high-performance nanofiber-loaded metal-organic frame composites,and the properties of its degradation chemical warfare agent simulator were studied.The specific research results are as follows:(1)MOF-808@PAN nanofiber composites were prepared by using two systems(DMF-formic acid system and TFA system).By comparing the morphology,structure and properties of the two samples,it was found that the two systems could load MOF-808particles on the surface of PAN nanofibers,but the damage of TFA system to the fiber membrane was great,and the prepared composites had no mec hanical strength.However,the MOF-808@PAN nanofiber composites made by DMF-formic acid system have better mechanical properties,but this method has some problems,such as the bonding between MOF-808 and fiber materials is not close,and it is easy to fall off after ultrasonic cleaning.(2)The surface of PAN nanofiber membrane was modified by polydopamine,and the polydopamine coating layer was formed on the surface of PAN/PDA nanofiber membrane by using the super adhesion of polydopamine,and then the M OF-808 particles of DMF-formic acid system were grown in situ on the surface of PAN/PDA nanofiber membrane to prepare MOF-808@PAN/PDA composites.This method significantly improves the load fastness of MOF-808.The surface modification time and MOFs in-situ growth time were discussed.From the characterization results of morphology,mechanical properties and catalytic degradation test,the optimum surface modification time is 16 h and the best in-situ growth time is 16 h.Under this parameter,the mechanical properties can reach 19.3MPa,the elongation at break is 17.9%,the specific surface area of BET is 648 m~2/g,and the degradation rate of DMNP is 99.9%(8 min).However,an important problem has been noticed in the preparation of MOF-808@PAN/PDA composite membrane:in the solvothermal synthesis reaction,the polydopamine coating on the surface of the composite is easy to be destroyed by strong polar solvent DMF,resulting in a large amount of elution,affecting the effect of surface modification,and pollution of the reaction solution,which may affect the secondary use of the mixed solution in industrial production.(3)In order to avoid the damage of DMF in solvothermal reaction solution to the polydopamine layer on the surface of fiber membran e,dopamine was added into polymer PAN spinning solution in advance,and PAN/DA nanofiber membrane was prepared by electrospinning,and then solvothermal synthesis reaction was carried out to realize the in-situ growth of MOFs on the surface of fiber membrane to prepare MOF-808@PAN/DA composites.This method can also significantly improve the load fastness of MOF-808.The process of dopamine addition and in-situ growth time were explored.From the characterization results of morphology,mechanical properties and catalytic degradation test,the optimum addition of dopamine was 30%,and the best in-situ growth time was 16h.Under this parameter,the mechanical properties can reach 21.8 MPa,the elongation at break is 37.8%,the specific surface area of BET is 1141 m~2,and the degradation rate of DMNP is 99.9%(8 min).Compared with the polydopamine modified composite MOF-808@PAN/PDA,the comprehensive properties of the composite materials are improved:the mechanical index is improved,the elongation at break is increased by 111%,the specific surface area of the composite is increased by 76.1%,and the degradation half-life of the chemical warfare agent simulator DMNP is shortened from 56.8 s to 50.2 s.