The photocatalytic activity of novel, substituted porphyrin/TiO2-based composites (original) (raw)
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Dyes and Pigments, 2009
Two series of novel meso-substituted porphyrins, namely 5,10,15,20-tetra[4-(3-phenoxy)-propoxy]phenyl porphyrin, the structural analogue 5,10,15,20-tetra[2-(3-phenoxy)-propoxy]phenyl porphyrin and their Co(II) Cu(II) and Zn(II) complexes were synthesized. The compounds were characterized using various spectroscopic techniques and their molecular structure was proposed based on density functional theory calculations. The diverse properties of the porphyrin derivatives result from the different stereochemistry of the particular substituents at the meso site on the macrocycle and are controlled also by the coordinated metal. The 1 H NMR spectrum of the free-base porphyrin showed a complicated spinsplitting. The photocatalytic activities in degradation of 4-nitrophenol were investigated using polycrystalline TiO 2 impregnated with the porphyrins and metalloporphyrins. The Cu(II) porphyrin was a more effective sensitizer than other metal containing compounds (M ¼ Co, Zn) as well as the free-base. Photocatalytic activity was also influenced by spatial positions of the substitutions on the porphyrin molecules.
Applied Catalysis B: Environmental, 2007
The novel porphyrins 5,10,15,20-tetra-[4-(3-phenoxy)-propoxy]phenyl porphyrin, H 2 Pp(a) and 5,10,15,20-tetra-[2-(3-phenoxy)-propoxy]phenyl porphyrin, H 2 Pp(b) and their corresponding copper(II) complexes CuPp(a), CuPp(b) were synthesized and characterized by using various spectroscopic techniques. The photocatalytic activity of polycrystalline TiO 2 samples impregnated with H 2 Pp(a), H 2 Pp(b), CuPp(a) and CuPp(b) 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. The maximum photocatalytic activity was obtained using TiO 2 loaded with a monolayer of the copper porphyrin CuPp(b) in the amount of 18 mmol per gram of TiO 2 .
Photocatalytic Activity of a Porphyrin/TiO2 Composite in the Degradation of Pharmaceuticals
Applied Catalysis B: Environmental
Two separate methods were used to prepare a tetra(4-carboxyphenyl)porphyrin (TCPP)-TiO2 composite. In method A TCPP was absorbed onto TiO2 in methanol at room temperature, whilst in method B TCPP was absorbed onto TiO2 in dimethylformamide (DMF) at reflux. Both composites exhibited the same physical and chemical characteristics as shown by FT-IR, SEM and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of both composites was then determined by HPLC monitoring of the photo-degradation of the pharmaceutical Famotidine under both visible and solar light irradiation. The recyclability of the composites was also examined by recovery of the composite post-reaction, although the absorbed TCPP was found to partially degrade, the recycled composite still exhibited catalytic behaviour. All reactions were monitored by HPLC which revealed that the photodegradation of Famotidine by the TCPP–TiO2 composites does not lead to complete mineralisation, but instead generates ...
The Journal of Physical Chemistry B, 2005
Characterization of polycrystalline TiO 2 bare or porphyrin impregnated powders, used as photocatalysts for the degradation of 4-nitrophenol (4-NP) in aqueous suspension, was performed by time-resolved microwave conductivity (TRMC) measurements and electronic paramagnetic resonance (EPR) and X-ray photoelectron (XPS) spectroscopies. The presence of porphyrin sensitizers, as the metal-free or Cu [5,10,15,20-tetra (4tert-butylphenyl)] porphyrin, impregnated onto the TiO 2 surface improved the photocatalytic activity of the bare TiO 2 . TRMC measurements indicate that the number and lifetime of the photoinduced excess charge carriers increase in the presence of the macrocycles, and EPR and XPS spectroscopies support the mechanistic hypotheses based on the photoreactivity experiments.
Surfaces and Interfaces, 2020
TiO 2 nanoparticles in anatase-brookite phases were synthesized, modified with (5,10,15,20-tetrakis(carboxyphenyl)porphyrinate)manganese(III)-[Mn III (T4CPP)] and (5,10,15,20-tetrakis(carboxyphenyl))porphyrin-H 2 T4CPP, and their photocatalytic activities were evaluated by the degradation of methylene blue dye. The prepared materials were characterized by XRD, Raman, gas adsorption, HRTEM-EDS, EELS, fluorescence spectroscopy, and XPS. These techniques provide direct evidence that crystalline TiO 2 nanoparticles with high specific surface area were prepared from aqueous TiCl 4 precursor and had their surfaces modified by porphyrins. Differences in textural properties between TiO 2 samples modified with H 2 T4CPP and [Mn III (T4CPP)] evidenced the role of the Mn III and carboxyl groups in anchoring these molecules on the TiO 2 surface. This molecular configuration was important for understanding the photocatalytic performance associated with the charge transfer between TiO 2 and the sensitizers.
Research on Chemical Intermediates, 2007
Photodegradation of organic compounds in water solutions by means of economically advantageous and environment-friendly processes is a topic of growing interest. In recent years a great attention has been devoted to TiO 2 -based photocatalysts for the oxidative degradation of various organic pollutants. In this context, we have prepared new photo-catalytic polycrystalline TiO 2 systems impregnated with sensitizers, i.e., copper, iron or manganese porphyrins, and investigated their photoactivity for 4-nitrophenol oxidation compared with that of bare TiO 2 . A significant improvement of the photoreactivity was observed in the case of TiO 2 impregnated with copper porphyrin, while only a slight beneficial effect was observed in the case of iron porphyrin. In contrast, the presence of manganese porphyrin appeared to be detrimental.
2021
The absence of a secure long-term sustainable energy supply is recognized as a major worldwide technological challenge. The generation of H2 through photocatalysis is an environmentally friendly alternative that can help solve the energy problem. Thus, the development of semiconductor materials that can absorb solar light is an attractive approach. TiO2 has a wide bandgap that suffers from no activity in the visible spectrum, limiting its use of solar radiation. In this research, the semiconductor absorption profile was extended into the visible region of the solar spectrum by preparing porphyrin-TiO2 (P-TiO2) composites of meso-tetra(4-bromophenyl)porphyrin (PP1) and meso-tetra(5-bromo-2-thienyl)porphyrin (PP2) and their In(III), Zn(II) and Ga(III) metal complexes. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were performed on the porphyrins to gain insight into their electron injection capability. The results demonstrate that P...
Phororedox and photocatalytic processes on Fe(III)–porphyrin surface modified nanocrystalline TiO2
Journal of Molecular Catalysis A: Chemical, 2000
Surface derivatization of titanium dioxide nanoparticles with a Fe III-porphyrin has been carried out following a new procedure whereby the complex, rather than the surface, contains the aminopropylsilane functional group. This avoids the problems of surface deactivation by silane groups, reported in earlier investigations, on analogous systems. Characterization of the light-transparent dispersions by laser flash photolysis, UV-vis spectroscopy and photo-electrochemical methods has shown that the nature of the solvent is an important parameter in determining the redox processes involving the grafted Ž. porphyrin. In particular, one observes marked effects on the stability of the Fe II-porphyrin formed upon capture of the photogenerated electrons. The photocatalytic activity of the composite systems was assessed in the process of monooxygenation of cyclohexane and cyclohexene by molecular oxygen. The bonded porphyrin enhances the yield and the formation of the monooxygenation products with respect to total degradation to CO for both the examined substrates. On this basis, we 2 can claim an increase in the efficiency and selectivity with the composite photocatalytic system. In the case of cyclohexane, we observed, in addition, that the iron-porphyrin complex also changes the selectivity of the process, increasing the alcohol to ketone ratio.
Unraveling Structure–Performance Relationships in Porphyrin-Sensitized TiO2 Photocatalysts
Nanomaterials
Over the years, porphyrins have arisen as exceptional photosensitizers given their ability to act as chlorophyll-mimicking dyes, thus, transferring energy from the light-collecting areas to the reaction centers, as it happens in natural photosynthesis. For this reason, porphyrin-sensitized TiO2-based nanocomposites have been widely exploited in the field of photovoltaics and photocatalysis in order to overcome the well-known limitations of these semiconductors. However, even though both areas of application share some common working principles, the development of solar cells has led the way in what is referred to the continuous improvement of these architectures, particularly regarding the molecular design of these photosynthetic pigments. Yet, those innovations have not been efficiently translated to the field of dye-sensitized photocatalysis. This review aims at filling this gap by performing an in-depth exploration of the most recent advances in the understanding of the role play...