Asymmetric Triple-Atom Sites Confined in Ternary Oxide Enabling Selective CO₂ Photothermal Reduction to Acetate

Light-induced heat is largely neglected in traditional photocatalytic systems, especially for the thermodynamically and kinetically challenging CO₂ reduction to C₂ fuels. Herein, we first design asymmetric Metal₁-O-Metal₂ triple-atom sites confined in phenakite to facilitate C-C coupling and employ photoinduced heat to increase molecular thermal vibration and accelerate CO₂ reduction to C₂ fuels. Using O-vacancy-rich Zn₂GeO₄ nanobelts as prototypes, quasi in situ Raman spectra disclose the Zn-O-Ge triatomic sites are likely the reactive sites. Density functional theory calculations reveal that the asymmetric Zn-O-Ge sites could promote C-C coupling through inducing distinct charge distributions of neighboring C₁ intermediates, whereas the created O vacancies could lower the energy barrier of the rate-determining hydrogenation step from 1.46 to 0.67 eV. Catalytic performances under different testing conditions demonstrate that light initiates the CO₂ reduction reaction. In situ Fourier-transform infrared spectra and D₂O kinetic isotopic effect experiments disclose that light-induced heat kinetically triggers C-C coupling and accelerates OCCO* hydrogenation via providing abundant hydrogen species. Consequently, in a simulated air atmosphere under 0.1 W/cm² illumination at 348 K, the O-vacancy-rich Zn₂GeO₄ nanobelts demonstrate an acetate output of 12.7 μmol g⁻¹ h⁻¹, a high acetate selectivity of 66.9%, a considerable CO₂-to-CH₃COOH conversion ratio of 29.95%, and a stability of up to 220 h.