In‐Situ Growth of Metallocluster Inside Heterometal‐Organic Cage to Switch Electron Transfer for Targeted CO2 Photoreduction

Abstract 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 metallocluster‐based architectures, and the in situ endogenous generation of metal clusters. Herein, based on the hard‐soft‐acids‐bases (HSAB), the metallocluster‐based heterometallic MOC ( Cu 3 VMOP ) constructed of [Cu 3 OPz 3 ] + and [V 6 O 6 (OCH 3 ) 9 (SO 4 )(CO 2 ) 3 ] 2− clusters was obtained by one‐pot method. In addition, Cu 4 I 4 was generated in situ in the cage to form Cu 4 I 4 @Cu 3 VMOP by the coordination‐driven hierarchical self‐assembly strategy. As catalysts for CO 2 reduction, Cu 3 VMOP produces HCOOH and CH 3 COOH as the main reduction product with yield of CH 3 COOH up to 0.9 mmol g −1 , ranking among the highest value of reported materials, whereas Cu 4 I 4 @Cu 3 VMOP exhibited targeted CO 2 ‐to‐HCOOH conversion with 100 % formic acid selectivity and the yield outperforms that of Cu 3 VMOP by 5 fold. Theoretical calculations and femtosecond time‐resolved transient absorption reveal that endogenous Cu 4 I 4 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 CO 2 to formic acid.