Bimetallic Single Atoms for Mild Anaerobic Photocatalytic C(sp3)–H Activation in C–C Coupling Reaction

Achieving efficient activation of inert C(sp³)–H bonds while preserving the reactivity of intermediates remains a substantial challenge. Herein, we present bimetallic Pt and Pd single atoms on commercial P25-TiO₂ (PtPdSA-TiO₂) to produce active surface lattice oxygen species for effective and mild anaerobic activation of C(sp³)–H bonds and generation of targeted intermediates, facilitating the C–C coupling reaction of acetone into a high-value-added 2,5-hexanedione (HDN, C₆ compound) and hydrogen. The in situ ESR, in situ ATR-IR and theoretical studies demonstrate that the surface oxygen species bridging Pt and Pd single atoms can effectively balance the activation energy of C(sp³)–H and the formation energy of free radical intermediates through bonding with the key −CH₂COCH₃ intermediate, contributing to a remarkable rate of 5.98 mmol g_{photocatalyst}^–1 h^–1 for the production of HDN with excellent selectivity (98.2%) on PtPdSA-TiO₂ compared to previously reported PtSA-TiO₂ (3.48 mmol g_{photocatalyst}^–1 h^–1) or PdSA-TiO₂ (2.78 mmol g_{photocatalyst}^–1 h^–1). Additionally, the PtPdSA-TiO₂ equipped in an outdoor solar-tracking reactor shows an HDN-production rate of 6.48 mmol g_{photocatalyst}^–1 h^–1 under the irradiation of concentrated sunlight (∼1800 mW cm^–2), validating the feasibility of the system in real solar conditions.