Photocatalytic Chemoselective Hydrogenation of Benzaldehyde and 5-Hydroxymethylfurfural by Alcohols with the Participation of Crystalline Carbon Nitride

Abstract

It has been established that crystalline carbon nitride (CCN) in acidic solutions of C1-C4 alcohols in the presence of a palladium cocatalyst exhibits high photocatalytic activity in the process of chemoselective hydrogenation of benzaldehyde (BA) and 5-hydroxymethylfurfural (HMF) to benzyl alcohol and 2,5-dihydroxymethylfuran, respectively. The apparent quantum yield of BA conversion reaches ~90 % in ethanol under optimal conditions, while HMF reaches 30% (at λ_irr = 405 nm). A probable process scheme is proposed, which involves the initiation of transformations of substrate molecules with the participation of photogenerated charges, in particular, oxidation of alcohols by holes of the CCN valence band, reduction of carbonyl groups by photogenerated electrons, and further transformations of intermediate compounds of a radical nature with the formation of final products.