Micro-scale spatial location engineering of COF–TiO2 heterojunctions for visible light driven photocatalytic alcohol oxidation

Abstract

Herein, we report the design and fabrication of QH-COF@TiO₂ and TiO₂@QH-COF (QH-COF: tetrahydroquinoline-linked COFs) core–shell structured heterojunctions for photocatalytic oxidation of alcohols. For the first time, the spatial location of two semiconductors either in the core or on the shell is precisely designed, and their corresponding photocatalytic performance has been well investigated. For photocatalytic benzyl alcohol oxidation, the activity of QH-COF@TiO₂ is almost three times higher than that of TiO₂@QH-COF (reaction rate: 1.19 vs. 0.44 mmol g⁻¹ h⁻¹), although they exhibit similar capability for light harvesting and charge separation. The higher photocatalytic activity of QH-COF@TiO₂ is due to its easier donation of electrons to O₂. A similar tendency was also observed for the visible-light photocatalytic aerobic cross-dehydrogenative coupling reaction. Our spatial location engineering of semiconductor heterojunctions provides an efficient strategy that facilitates the modulation of charge separation and mass diffusion to enhance the photocatalytic activity of semiconductors.