Novel Substituted Porphyrins And Metalloporphyrins: Synthesis, Characterization And Photo-catalytic Activity Of Their TiO₂-based Composites

Nature has chosen porphyrin as the photosynthetic center for green plants and combine-release oxygen center for heme in their long process of development and evolution. The conjugated macrocycle,which is built by 20 carbon atoms and 4 nitrogen atoms,prospers the whole nature and the chemical research field due to its particular property,so it has attracted more and more attention.Meanwhile,in the inorganic research area,TiO₂ shows all kinds of unique properties and enjoys high popularity in the research field since Fujishima and Honda discovered that the TiO₂ electrode has the capacity of photo-induced decomposition of water in 1972.TiO₂ becomes one of the most potential photocatalytic materials at present due to its photocatalytic activity,high stability,innocuity and accessibility.As a kind of organic-inorganic composite photosensitive catalytic material, Porphyrins-TiO₂ brings more and more hope to people as it develops.This strong-strong united new-style material can degrade the organic pollution molecules efficiently in aqueous solutions,decrease the total organic carbon(TOC),and purify water under solar light.However,Porphyrin-TiO₂ photocatalyst is still being tested in the laboratory for its photodegradation,and it will be a long time before industrial application.Some detailed problems in the process of photodegradation are still unknown,especially the influence of porphyrin structures on potocatalytic efficiency and the mechanism in this process.We synthesized some porphyrins and impregnated them onto the TiO₂ surface to produce a porphyrin-TiO₂ pohotocatalyst,to investigate the influence of porphyrin structures on potocatalytic efficiency by photo-degradation of 4-nitrophenol(4-NP) under visible light,and summarize the characteristics and rules of the influence and put forward some reflection and inspiration which can be used as reference for future research in this field.The main work in this paper is as follows:1.Three new aldehydes and twelve new porphyrins have been synthesized and characterized by various spectroscopic techniques.The relationship between the structure of porphyrins and their properties have been discussed and analyzed.The number of substitutions is one,two,three,and four respectively and the position of the substitutions is in the tetraphenylporphyrin's ortho-,meta- and para- sites respectively.Changes in the terms of the position and number of substituents help to discover the efficiency of the porphyrins sensitization.2.Some metalloporphyrins have been synthesized and characterized,such as Cu(â…¡), Zn(â…¡),Fe(â…¢),Co(â…¡),Ni(â…¡),Mn(â…¢),Sn(â…£),etc.3.The photocatalytic activity of polycrystalline TiO₂ samples which are impregnated with porphyrins(metal free porphyrins and metalloporphyrins) as sensitizers have been investigated by carrying out the photo-degradation of 4-nitrophenol(4-NP) as a probe reaction in aqueous suspension and under visible light.Factors like the appropriate position and the number of substitutions,their spacer length,the type of the coordinated metal,and the amount of the porphyrin can influence the efficiency of TiO₂-porphyrins systems,but the coordination of metal is the key factor.4.We summarized the reasons for the different photocatalytic degradation effect of porphyrin-TiO₂,which will provide useful thought and reference for future researh5.At the same time,we summarized the reaction mechanism of the photo-degradation via some references and the experiment results.