Selective organic transformation under mild conditions constitutes a challenge in green chemistry, especially for alcohol oxidation, which typically requires environmentally unfriendly oxidants. Here, we report a new plasmonic catalyst of Au supported on BiOCl containing oxygen vacancies. It photocatalyzes selective benzyl alcohol oxidation with O2 under visible light through synergistic action of plasmonic hot electrons and holes. Oxygen vacancies on BiOCl facilitate the trapping and transfer of plasmonic hot electrons to adsorbed O2, producing •O2– radicals, while plasmonic hot holes remaining on the Au surface mildly oxidize benzyl alcohol to corresponding carbon-centered radicals. The hypothesized concerted ring addition between these two radical species on the BiOCl surface highly favors the production of benzaldehyde along with an unexpected oxygen atom transfer from O2 to the product. The results and understanding acquired in this study, based on the full utilization of hot charge carriers in a pla...

New Reaction Pathway Induced by Plasmon for Selective Benzyl Alcohol Oxidation on BiOCl Possessing Oxygen Vacancies.

Photocatalysis: a promising route for 21st century organic chemistry

Photocatalysis with organized systems for the oxofunctionalization of hydrocarbons by O2.

This article reviews recent advances in selective organic transformations, both in gas and liquid media, using titanium oxide-based photocatalysts. Several photocatalytic reactions, such as oxidation, reduction, and coupling reactions, proceed highly efficiently and selectively without requiring harmful and dangerous chemical reagents and without harmful byproducts. In addition, multistep processes usually required for conventional synthesis of various kinds of valuable compounds can be simplified to a one-pot reaction when in photocatalytic systems. Photocatalytic transformations will therefore play a very important role for organic synthesis in an economically and environmentally friendly way. This review article demonstrates that titanium oxide-based photocatalysts have a great potential as a versatile tool in “green” organic synthesis.

Selective organic transformations on titanium oxide-based photocatalysts

Photo-oxidation of toluene has been carried out in gas–solid regime by using polycrystalline anatase TiO2 as the catalyst. The reacting gaseous mixture was toluene, air and water in various molar ratios. A pyrex fixed-bed continuous photoreactor irradiated by a medium pressure Hg lamp was used for performing the photoreactivity experiments. The main oxidation product was benzaldehyde but benzene, benzyl alcohol and traces of benzoic acid, phenol and unidentified compounds were also detected. The molar conversion to benzaldehyde with respect to the initial amount of toluene was ca. 20% in the best experimental conditions. Benzene was produced only as a transient product during the first 3–4 h of irradiation. The dependence of feed composition and flow rate on the toluene fractional conversion was investigated. Selected experiments were performed by using N2 or CO2 instead of air. The presence of oxygen was essential for the occurrence of the photoreaction while water played an important role in order to maintain the catalyst activity. Moreover, a Fourier-transform infrared spectroscopy (FT-IR) investigation was carried out simulating the experimental conditions used during the photoreactivity experiments. The results indicated that toluene is weakly stabilised on the hydrated TiO2 particles by hydrogen-bonding with surface hydroxyl groups, and that it is photo-oxidised to benzaldehyde only in the presence of surface OH groups.

Photocatalytic oxidation of gaseous toluene on anatase TiO2 catalyst: mechanistic aspects and FT-IR investigation

The heterogeneous photocatalytic oxidation of neat toluene and 4-picoline in liquid organic oxygenated dispersions containing pure or iron-doped titania photocatalysts has been studied in a photochemical reactor radiating predominantly at 365–366 nm. The investigation correlates experimental conditions such as structural aspects, surface properties, concentration and chemical nature of the photocatalysts, and illumination times, with chemical yields and selectivity of products. For toluene, the main photocatalytic products found were benzaldehyde, benzyl alcohol and benzoic acid. In particular, our results show that traces of water present in the reaction system play an important role in the distribution of products. Likewise, the important role of the adsorption effects in photocatalysis based on semiconductors is emphasized. Thus, differences in the affinity and mode of the adsorption of different molecules (i.e., toluene, picolines) should give rise to differences in the distribution of the reaction products.

Partial or complete heterogeneous photocatalytic oxidation of neat toluene and 4-picoline in liquid organic oxygenated dispersions containing pure or iron-doped titania photocatalysts

UV irradiation of 2-furoic acid was carried out in the presence of TiO2 and hypochlorite ions (and methanol) and in the absence of oxygen. An endoperoxide compound was photogenerated; this endoperoxide underwent subsequent transformations. The significance of the introduction of oxygen into organic substrates using chlorinated TiO2 surfaces as photocatalysts is discussed.

Oxidation of 2-furoic acid via singlet oxygen generated photochemically

Phenacylthiourea and N-thiazolyl derivatives of 2-amino-2-deoxy-D-glucose

Summary We report here results on the photocatalytic oxidation by oxygen of neatliquid toluene, under UV-irradiation, by using unloaded and iron-loaded titania catalysts. Several experimental conditions have been selected to investigate parameters which can influence the chemical yields and the distribution of products; particular attention has been devoted to investigate the evolution of chemical yields and selectivity by extending the irradiation times up to 12 h. A discussion on the effects of structural features and the concentration of catalysts is reported. The role of water has been also investigated.

(Heterogeneous) Photocatalytic Oxidation of Toluene Using Pure and Iron-Doped Titania Catalysts

The photochemical degration of diphenylmercury and monophenylmercury compounds in water—acetonitrile (1:1) media in an air-equilibrated atmosphere was studied. The photoprocess involves sequential dephenylation to inorganic forms of mercury, with the subsequent formation of several organic products, most of them pollutants. The ecological impact of this photoprocess is emphasized.

M.A. Pradera Adrian

Papers

Partial or complete heterogeneous photocatalytic oxidation of neat toluene and 4-picoline in liquid organic oxygenated dispersions containing pure or iron-doped titania photocatalysts

Oxidation of 2-furoic acid via singlet oxygen generated photochemically

Phenacylthiourea and N-thiazolyl derivatives of 2-amino-2-deoxy-D-glucose

(Heterogeneous) Photocatalytic Oxidation of Toluene Using Pure and Iron-Doped Titania Catalysts

UV photolytic degradation of phenylmercury compounds in water-acetonitrile (1:1) media