Preparation Of Thermally Stabilized Electrospun Pan Nanofibers Supported Mofs Based Photocatalysts And Their Photocatalytic Performance Towards Cr(Ⅵ) Reduction

With the development of industry,excessive Cr（VI）into water has caused serious water pollution in recent years.This can be a serious threat to the health of animals and plants and the stability of the ecosystem.Effective treatment of Cr（VI）in water is one of the urgent problems in water environmental governance in China.Among the numerous Cr（VI）treatment methods,the photocatalytic method with continuous solar energy driven photocatalyst to reduce the highly toxic Cr（VI）to the low-toxic Cr（Ⅲ）,which is green,safe and does not cause secondary pollution.The design and construction of new high efficiency photocatalyst is a research hotspot of photocatalytic treatment technology.Metal-Organic Frameworks（MOFs）is a potential new type of photocatalyst due to the existence of photogenerated electrons transfer mechanism from ligands to metal centers.However,there are still deficiencies that MOFs as photocatalyst for the removal of pollutants in water.For example,most MOFs exist in the form of powder,which leads to their agglomeration in the practical application process thereby affects their photocatalytic activity.And it is difficult to separate from water for recycling.In addition,Most MOFs themselves have unsatisfactory visible light response or fast recombination speed of electrons and holes,resulting in unsatisfactory photocatalytic effects.Therefore,in this paper,the removal of Cr（VI）was taken as the object,and the activity and recoverability of photocatalytic degradation of Cr（VI）under visible light of MOFs were improved by constructing flexible MOFs membrane or MOFs heteroconjunctiva.The specific research work is as follows:（1）Using thermally stabilized polyacrylonitrile（TSPAN）electrospun nanofibers as the support,the flexible TSPAN@UIO-66-NH₂ photocatalyst was successfully prepared by the solvothermal in-situ growth method,and the photocatalytic reducing of Cr（VI）under visible light was investigated.The results show that the polyacrylonitrile（PAN）electrospinning nanofibers in certain conditions on the thermal stability of treatment can improve its resistance to organic solvent and heat resistance.In addtion,the pyridine ring and hydronaphthyridine ring formed during the thermal stabilization process can provide abundant nucleation points for the in-situ growth of UIO-66-NH₂ crystals,and the dense UIO-66-NH₂film layer was obtained on the surface of the fiber.The photocatalytic activity of the TSPAN@UIO-66-NH₂ fiber membrane is better than that of powder UIO-66-NH₂ under visible light,the photocatalytic reduction of Cr（VI）efficiency can reach 93%within 180minutes and the reduction rate is 2.3 times that of powder UIO-66-NH₂.（2）In order to improve the photocatalytic activity of UIO-66-NH₂,Bi OCl was introduced on the surface of TSPAN@UIO-66-NH₂ photocatalyst by solvothermal method to construct the TSPAN@UIO-66-NH₂@Bi OCl photocatalyst of heterojunction film material based on electrospun TSPAN nanofibers.The results showed that Bi OCl can combine with UIO-66-NH₂ on the TSPAN fibers through the C-Cl bond,forming a uniformly distributed nanosheet structure on its surface.Under visible light,the TSPAN@UIO-66-NH₂@Bi OCl can effectively improve the separation efficiency of photogenerated electron holes due to its heterojunction structure.The TSPAN@UIO-66-NH₂@Bi OCl has better reduction efficiency of Cr（VI）compared with TSPAN@UIO-66-NH₂ reduction rate can reach 97%within 90minutes.Through the capture experiment and the investigation of the effect of p H on the photocatalytic performance,it is found that the photo-generated electrons play a major role in the reduction of Cr（VI）,and the photocatalytic reduction activity is higher under acidic conditions.In addition,the TSPAN@UIO-66-NH₂@Bi OCl also has good light stability and easy recycling like the TSPAN@UIO-66-NH₂.