Harnessing Heterogeneous Asymmetric Oxide Interface for Efficient Photodehydrogenation of Isopropanol through α-C-H Bond Activation

Abstract

Photocatalytic α-C-H activation of alcohols to form aldehydes and ketones represents an important synthetic pathway, although the selective formation of C-centered radicals remains challenging due to competing O-H activation processes. While extensive research has explored heterojunction band alignment, charge transfer directionality, and component-specific redox reactions, the atomic structure at interfaces and its catalytic role have received limited attention. Here, we demonstrate a TiO₂-CuO heterojunction photocatalyst that achieves exceptional selectivity in the oxidation of isopropanol to acetone, with a hydrogen production rate of approximately 4400 μmol/g/h. Through complementary characterization using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and ab initio molecular dynamics (AIMD), we identify the formation of asymmetric Ti-O(H)-Cu⁺ units at the TiO₂/CuO heterojunction interface. In situ EPR reveals a ·C(OH)(CH₃)₂ radical intermediate, confirming that the reaction proceeds via selective hydrogen atom transfer (HAT) of the α-C-H bond in isopropanol, in contrast to that of TiO₂ or CuO, which proceed via hydrogen extraction of the OH group. These mechanistic insights into interface-mediated catalysis provide new design principles for engineering atomic-scale catalytic interfaces, offering new opportunities for developing next-generation photocatalysts across diverse catalytic applications.