Surface Polarons for Synergistic Kinetic and Thermodynamic C-H Bond Oxidation

The photocatalytic oxidation of the inert C-H bond remains a paramount challenge, plagued by both rapid carrier recombination in kinetics and slow surface reactions in thermodynamics. Herein, we present a conceptually distinct strategy to simultaneously resolve both core challenges by tailoring surface polarons on photocatalysts via anchoring atomically dispersed Mn sites onto a low-crystallinity SnO₂ support. These atomic sites induce localized lattice distortions via strong electron-phonon coupling, generating surface small polarons that serve a dual function. Kinetically, these polarons trap photogenerated electrons within picoseconds, suppressing bulk recombination and establishing a dominant, long-lived interfacial charge transfer channel (∼65 ps) directly to the reactants, as revealed by femtosecond transient absorption spectroscopy (fs-TAS). Thermodynamically, the polaronic field strengthens toluene adsorption (adsorption energy strengthened from -0.49 to -0.91 eV) and polarizes the C-H bond, significantly lowering the activation barrier, as confirmed by density functional theory (DFT) calculations and in situ DRIFTS. Consequently, the Mn₁/SnO₂ catalyst achieved about 100% efficiency in the challenging toluene oxidation with a high weight hourly space velocity (WHSV) of 60,000 mL·g_cat^-1·h^-1 under a continuous flow system. Additionally, the Mn₁/SnO₂ catalyst exhibited exceptional stability over 600 min and resistance to relative humidity (RH) ranging from 5% to 90%. This work elucidated the fundamental role of surface polarons in harmonizing charge dynamics with surface catalysis, offering a powerful strategy for designing highly efficient and robust photocatalysts for challenging chemical transformations.