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

Photocatalytic reduction of carbon dioxide (CO2) provides a promising strategy for producing high-value chemical and fuel. However, developing high-performance photocatalysts for CO2 reduction remain a great challenge due to the poor stability of reaction intermediates. Herein, we present an anionic coordination strategy to facilitate intermediates by the construction of halogen-coordinated metal-organic cages (Ni8L12X4, X = Cl, Br, I). Theory calculations show that the formation of the *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 Ni d orbitals and iodide p orbitals, facilitating electron transfer from Ni center to the adsorbed CO2 and promote 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-coordinated 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.