Anionic Coordination-Regulated Metal-Organic Cages for Efficient CO2 Photoreduction.

Photocatalytic reduction of carbon dioxide (CO2) provides a promising strategy for producing high-value chemicals and fuels. However, developing high-performance photocatalysts for CO2 reduction remains a great challenge due to the poor stability of reaction intermediates. Herein, we present an anionic coordination strategy to facilitate the stabilization of intermediates by constructing halogen-coordinated metal-organic cages (MOCs) (Ni8L12X4, X = Cl, Br, I). Theoretical calculations show that the formation of *COOH intermediate is the rate-limiting step and halogen coordination effectively regulates the energy barrier for this reaction. Notably, iodide anions significantly reduce the energy gap between the Ni d and iodide p orbitals, enhancing electron transfer from the Ni center to adsorbed CO2 and promoting the production of *COOH. As a result, Ni8L12I4 demonstrates superior performance with a CO production rate of 2680.23 µmol g-1 h-1 and 95% selectivity, outperforming Cl- and Br-coordinated Ni MOC by 200- and 5-fold, respectively. This work opens a new coordination engineering strategy for fabricating efficient photocatalysts for CO2 reduction.