| The development of a green,efficient,and reusable photocatalyst is of great importance for degradation of organic pollutants in water.Metal-organic frameworks(MOFs)exhibit many excellent properties for their applications in wastewater treatment: high specific surface area,easy structure control,scattered active sites and excellent charge transfer performance,etc.However,MOFs generally suffer from difficulty in power recycling and photocatalytic performance that cannot meet the needs of practical applications.Based on the relationship between structure and performance,this work aimed to prepare photocatalytic material with practical application value.By means of in-situ growth and heterogeneous nucleation,MIL-88A@PA composite whose structure and comprehensive performance basically met the requirements was prepared,and the mechanism of composite structure regulation and its relationship with light absorption,charge transfer,and photocatalytic degradation performance were clarified.The main research contents are as follows:(1)Millimeter-sized PA spherical particles with interpenetrated macroporous structure were prepared by water-in-oil emulsion suspension polymerization,and the effects of polymerization temperature,dispersed phase volume and type of co-emulsifier on the internal pore structure of PA were investigated.The results showed that when the dispersed phase volume was 15 m L and the polymerization temperature was 70 °C,PA spherical particles(0.5 mm)with well-developed pore structure and good framework strength could be formed.N-isopropylacrylamide(NIPAM)as co-emulsifier reduced the pore size of PA from 3.0-5.0 μm to 0.8-1.2 μm.The amine group functional modification on the surface of the PA framework increased its surface energy,so that the PA completed the transition from hydrophobic to hydrophilic,which was beneficial to the transport and reaction of substances in water.(2)MIL-88A@PA composite was prepared by in situ growth of MIL-88 A on the surface of PA framework with amine functionalized PA as support material.The growth mode of MIL-88 A was regulated by the high surface energy of the PA framework and the confined space formed by the internal pores,the diameter of MIL-88 A was successfully reduced from 500-800 nm to50-100 nm,and the reduction in crystal size could promote the separation of photogenerated electron-hole pairs and expose more catalytic active sites,the photocatalytic activity of MIL-88 A was significantly improved.The photocatalytic active component MIL-88 A and the mass transfer channel provided by the PA macropore formed a structural coupling,which made the degradation rate of Rh B by MIL-88A@PA was 9.4 times than that of pure MIL-88 A.(3)In order to further improve the photocatalytic activity of MIL-88 A,polypyrrole(PPy)nanoparticle was introduced on the surface of PA framework to form conductive support material PA-PPy.The effect of the polymerization of pyrrole(Py)monomers of different masses on the pore structure of PA was analyzed,and the relationship between the introduction of PPy and the photocatalytic performance was clarified.The results revealed that MIL-88A@PA-PPy composite could completely degrade the organic pollutant Rh B within 40 min.In addition,the composite had good cycling stability due to the tight bonding of PA-PPy with MIL-88 A and the protection of the outer framework.After 5 photocatalytic degradation cycles,the degradation rate of the composite material only decreased by 2%. |
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