Programmable Photoreduction of CO₂-to-CH₄ Triggered by a Temperature-Adaptation Spin Polarization Electron Pump

Selective control of CO₂ photoreduction toward CO or CH₄ is essential for solar-to-fuel conversion. Reversible switching between these two products remains challenging because conventional photocatalysts cannot adjust charge behavior with temperature, and polar intermediates are insufficiently stabilized. A temperature-adaptation photocatalytic platform that acts as a spin polarization electron pump, delivering programmable interfacial electron injection and dynamically steering CO₂ reduction pathways in real time is reported. At low temperature, adaptive modulation increases interfacial electron accumulation at the reaction interface, extending the lifetime and reactivity of deep-pathway intermediates without altering catalyst composition. Consequently, product selectivity reversibly shifts from CO at high temperature to CH₄ at low temperature, enabling controlled access to either shallow or deep reduction products under reliably well-defined thermal conditions. Temperature-dependent photoluminescence and electron paramagnetic resonance demonstrate enhanced spin polarization and reduced charge recombination upon cooling, consistent with stronger interfacial electron retention. In situ infrared spectroscopy and ab initio molecular dynamics reveal that spin polarization-selective transfer bends CO₂ and induces C─O bond asymmetry, which facilitates CHO* formation and lowers the barrier for CO* hydrogenation to CH₄. Collectively, these findings establish a generalizable strategy that integrates spin polarization with temperature responsiveness to realize dynamically programmable product selectivity in solar-driven CO₂ conversion.