The Degradation And Reduction Of 4-NP By Porphyrin/Copper Porphyrin-TiO₂ Composite Photocatalyst

With the rapid development of science and technology,the production of industry and agriculture has greatly increased,and it has also brought about environmental pollution,especially,water pollution.Therefore,how to efficiently remove pollutants in water has become a research hotspot for researchers.Photocatalytic technology based on TiO₂ can utilize solar energy and widely used in water treatment.However,TiO₂ is a broadband semiconductor,it can only absorb ultraviolet light and cannot fully utilize solar energy.Porphyrins/copper porphyrins with conjugated delocalized structures have strong sbsorption in the visible light region,which can sensitize TiO₂ and increase its the absorptivity of light.In this paper,twokindsoffreeporphyrins5,10,15,20-tetra[3-?ethoxycarbonylpropyleneoxy?phenyl]porphyrin?H₂P1?,5,10,15,20-tetra[3-?carboxylpropyleneoxy?phenyl]porphyrin?H₂P2?and their corresponding copper porphyrins Cu?II?5,10,15,20-tetra[3-?ethoxycarbonylpropyleneoxy?phenyl]porphyrin?CuP1?and Cu?II?5,10,15,20-tetra[3-?carboxylpropyleneoxy?phenyl]porphyrin?CuP2?,were synthesized and characterized by EA,UV-vis,FT-IR,MS and ¹HNMR,and their molecular compositions and structures were determined.The TiO₂ sol was obtained by alcoholysis of n-butyl titanate at room temperature,and the corresponding porphyrin/copper porphyrin-TiO₂ composite photocatalysts?H₂P1-TiO₂,H₂P2-TiO₂,CuP1-TiO₂ and CuP2-TiO₂?were prepared by reacting with the synthesized porphyrins/copper porphyrins under solvothermal conditions.The synthesized composite photocatalysts were characterized by XRD,SEM,TEM,UV-vis-DRS,FT-IR,XPS,PLand BET,which demonstrate the successful loading of porphyrins/copper porphyrins.The photocatalytic activities and stabilities of the prepared composite photocatalysts were evaluated by photocatalytic degradation and reduction 4-NP in water,and the active species in the photocatalytic degradation of 4-NP were tested to explore the reaction mechanism.The results show that:?1?TiO₂ and composite photocatalysts after solvothermal reaction exposed the highly active?001?crystal plane;?2?The experimental synthesized porphyrins/copper porphyrins were successfully loaded on the surface of TiO₂.The porphyrins/copper porphyrins molecules interact with TiO₂ through Ti-O-C=O bond.;?3?The porphyrin/copper porphyri-TiO₂ composite photocatalyst has a heterojunction,which is beneficial to the tranfer of photogenerated electrons and holes,and makes the composite photocatalyst have enhanced photocatalytic activity;?4?The synthesized composite photocatalyst exhibited higher photocatalytic activity in the degradation of 4-NP,in which the CuP2-TiO₂ composite photocatalyst had the best performance;?5?The photocatalystic degradation of active species in the 4-NP experiment is h⁺mainly;?6?The synthesized composite photocatalysts can efficiently hydrogenate 4-NP to 4-AP;?7?After five cycles of experiments,the composite photocatalysts still maintain high photocatalytic activities in degradation and reduction of4-NP,and have high stabilities.