Precise Regulation of the Coordination Environment of Single Co(II) Sites in a Metal–Organic Framework for Boosting CO2 Photoreduction

While the coordination environment around catalytic metal sites plays a crucial role in catalysis, its precise design and modulation still remain a challenge. Herein, the coordinated N atom number around single Co sites installed on a UiO-type metal–organic framework has been modulated to afford UiO-Co-Nx (x = 2, 3, and 4) for photocatalytic CO2 reduction. Significantly, the photocatalytic performance is affected by the coordinated N atom number around the Co site, in which UiO-Co-N3 exhibits superior activity to the other counterparts. Photo-/electrochemical results support the fastest charge transfer kinetics between the photosensitizer and UiO-Co-N3. Theoretical calculations, together with the results acquired from in situ diffuse reflectance infrared Fourier transform spectra, manifest the lowest energy barriers of the rate-determining step and desorption energy of CO* over UiO-Co-N3 among all UiO-Co-Nx samples.