Synthesis of novel zinc porphyrins and their photocatalytic activity.

Purpose The purpose of this study is to investigate the effect of the spacer length of zinc porphyrin-TiO2 hybrids by photodegradation of methyl orange (MO) in aqueous solution under visible light.Design/methodology/approach 5-Mono-[4-hydroxyphenyl]-10,15,20-triphenylporphyrin was synthesized using Alder method. A new series of porphyrins and their corresponding zinc complexes (ZnPp) were obtained from 5-mono-[4-hydroxyphenyl]-10,15,20-triphenylporphyrin via nucleophilic substitution reaction. The ZnPp-TiO2 photocatalysts were prepared by loading ZnPp onto TiO2 and characterized by scanning electron microscope, X-ray diffraction, UV-vis diffuse reflectance spectrum and X-ray photoelectron spectroscopy.Findings The results indicated that zinc porphyrins were successfully loaded on the surface of TiO2 microsphere, which is crucial to enhance the activity of the catalytic composite under visible light. All the novel photocatalysts showed much enhanced photoactivity than bare TiO2. Among all the prepared ZnPp-TiO2, 5,10,15-triphenyl-20-[4-(4-naphthoxy)-butoxy]phenyl zinc porphyrin-TiO2 (4b) showed the highest photocatalytic activity for the degradation of MO.Research limitations/implications Synthesis of these zinc porphyrins had never been reported previously.Originality/value Four novel zinc porphyrin-TiO2 photocatalysts which could response to visible light in degradation of MO were synthesized using Alder method. The results show that the photocatalytic activity of 5,10,15-triphenyl-20-[4-(4-naphthoxy)butoxy] phenyl zinc porphyrin- TiO2 is higher than others. [ABSTRACT FROM AUTHOR]