In-situ Growth of Metallocluster inside Heterometal-organic Cage to Switch Electron Transfer for Targeted CO2 Photoreduction.

Construction of metal-organic cages (MOCs) with internal modifications is a promising avenue to build enzyme-like cavities and unlocking the mystery of highly catalytic activity and selectivity of enzymes. However, current interests are mainly focused on single-metal-node cages, little achievement has been expended to metalloclusters-based architectures, and the in situ endogenous generation of metal clusters. Herein, based on the hard-soft-acids-bases (HSAB), the metalloclusters-based heterometallic MOC (Cu3VMOP) constructed of [Cu3OPz3]+ and [V6O6(OCH3)9(SO4)(CO2)3]2- clusters was obtained by one-pot method. In addition, Cu4I4 was generated in situ in the cage to form Cu4I4@Cu3VMOP by the coordination-driven hierarchical self-assembly strategy. As catalysts for CO2 reduction, Cu3VMOP produces HCOOH and CH3COOH as the main reduction product with yield of CH3COOH up to 0.9 mmol g-1, ranking among the highest value of reported materials, whereas Cu4I4@Cu3VMOP exhibited targeted CO2-to-HCOOH conversion with 100% formic acid selectivity and the yield outperforms that of Cu3VMOP by 5 fold. Theoretical calculations and femtosecond time-resolved transient absorption reveal that endogenous Cu4I4 not only regulates orbital arrangements and enhances localized electron states to generate a long-lived charge-separated state, but also raises *CO coupling energy barrier, resulting in the targeted conversion of CO2 to formic acid.