Dual-productive photoredox cascade catalyst for solar hydrogen production and methylarene oxidation†

Abstract

Solar H₂ production during the transformation of organic compounds is a promising approach to supply both H₂ and organic chemicals necessary for a sustainable carbon neutral society. To create such a dual-productive photocatalytic system, we developed a photoredox cascade catalytic (PRCC) system by combining a dual-dye sensitized Pt–TiO₂ photocatalyst (DDSP) and an N-hydroxyphthalimide (NHPI) hydrogen atom transfer (HAT) catalyst. DDSP successfully evolved H₂ upon blue-light excitation and simultaneously oxidized NHPI to generate phthalimido-N-oxyl radicals (PINO˙) which produced oxidized methylarenes by the HAT reaction of the benzylic/allylic C–H bond, followed by a radical coupling reaction. The significantly higher activity of DDSP than that of single-dye sensitized analogue (SDSP) suggests that the dual-dye layer acted as an efficent separator to spatially divide the two reaction fields, while separating the electron–hole pairs produced by light absorption with high efficiency.