Toward a Sustainable Photocatalytic Oxidative Cleavage of Olefins Mediated by Nitrate Radicals: The Influence of the Physicochemical Features of the Photocatalyst

Abstract

The nitrate radical-mediated photocatalytic oxidative cleavage of the internal double bond of limonene to limononaldehyde was studied with respect to some of the features of different TiO2 photocatalysts. In particular, the influence of crystallinity, surface hydroxylation degree, surface modification, availability and potential of the photogenerated charges, and nitrate adsorption have been investigated by correlating them with the reaction selectivity. Results obtained from independent experiments show that the interaction of the organic molecules with the surface does not significantly influence the selectivity of the reaction, unlike what has been reported in the literature for other photocatalytic syntheses. On the other hand, the selectivity of the reaction is mainly influenced by the efficiency of the primary events of interfacial electron transfer, i.e., nitrate oxidation and silver reduction. Results highlight the key parameters to be modulated in order to design sustainable and selective olefin transformation to carbonyl compounds, whose actual industrial implementation is still far from being performed under green conditions.