Reversible Switching CuII/CuI Single Sites Catalyze High‐rate and Selective CO2 Photoreduction

Abstract Herein, we first design a model of reversible redox‐switching metal–organic framework single‐unit‐cell sheets, where the abundant metal single sites benefit for highly selective CO 2 reduction, while the reversible redox‐switching metal sites can effectively activate CO 2 molecules. Taking the synthetic Cu‐MOF single‐unit‐cell sheets as an example, synchrotron‐radiation quasi in situ X‐ray photoelectron spectra unravel the reversible switching Cu II /Cu I single sites initially accept photoexcited electrons and then donate them to CO 2 molecules, which favors the rate‐liming activation into CO 2 δ− , verified by in situ FTIR spectra and Gibbs free energy calculations. As an outcome, Cu‐MOF single‐unit‐cell sheets achieve near 100 % selectivity for CO 2 photoreduction to CO with a high rate of 860 μmol g −1 h −1 without any sacrifice reagent or photosensitizer, where both the activity and selectivity outperform previously reported photocatalysts evaluated under similar conditions.