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

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 CO2 reduction, while the reversible redox‐switching metal sites can effectively activate CO2 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 CuII/CuI single sites initially accept photoexcited electrons and then donate them to CO2 molecules, which favors the rate‐liming activation into CO2δ−, 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 CO2 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. [ABSTRACT FROM AUTHOR]