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 metalsitesplays a crucial role in catalysis, its precise design and modulationstill remain a challenge. Herein, the coordinated N atom number aroundsingle Co sites installed on a UiO-type metal-organic frameworkhas been modulated to afford UiO-Co-N- x (x = 2, 3, and 4) for photocatalytic CO2 reduction. Significantly, the photocatalytic performance is affectedby the coordinated N atom number around the Co site, in which UiO-Co-N-3 exhibits superior activity to the other counterparts. Photo-/electrochemicalresults support the fastest charge transfer kinetics between the photosensitizerand UiO-Co-N-3. Theoretical calculations, together withthe results acquired from in situ diffuse reflectance infrared Fouriertransform spectra, manifest the lowest energy barriers of the rate-determiningstep and desorption energy of CO* over UiO-Co-N-3 amongall UiO-Co-N- x samples.

Automated summary

The coordination environment around single Co sites in a UiO-type metal-organic framework is modulated to synthesize UiO-Co-N-x (x = 2, 3, and 4) catalysts for photocatalytic CO2 reduction. It is found that the photocatalytic performance is strongly influenced by the coordinated N atom number, with UiO-Co-N-3 exhibiting the highest activity. Photo-/electrochemical results confirm the fastest charge transfer kinetics between the photosensitizer and UiO-Co-N-3. Theoretical calculations and in situ diffuse reflectance infrared Fourier transform spectra reveal that UiO-Co-N-3 has the lowest energy barriers for the rate-determining step and desorption energy of CO* among all UiO-Co-N-x samples.