Nanoconfined tandem three-phase photocatalysis for highly selective CO 2 reduction to ethanol.

The conversion of CO 2 and H 2 O into ethanol with high selectivity via photocatalysis is greatly desired for effective CO 2 resource utilization. However, the sluggish and challenging C-C coupling hinders this goal, with the behavior of *CO holding the key. Here, a nanoconfined and tandem three-phase reaction system is established to simultaneously enhance the *CO concentration and interaction time, achieving an outstanding ethanol selectively of 94.15%. This system utilizes a tandem catalyst comprising an Ag core and a hydrophobic Cu 2 O shell. The hydrophobic Cu 2 O shell acts as a CO 2 reservoir, effectively overcoming the CO 2 mass-transfer limitation, while the Ag core facilitates the conversion of CO 2 to CO. Subsequently, CO undergoes continuous reduction within the nanoconfined mesoporous channels of Cu 2 O. The synergy of enhanced mass transfer, nanoconfinement, and tandem reaction leads to elevated *CO concentrations and prolonged interaction time within the Cu 2 O shell, significantly reducing the energy barrier for *CO-*CO coupling compared to the formation of *CHO from *CO, as determined by density functional theory calculations. Consequently, C-C coupling preferentially occurs over *CHO formation, producing excellent ethanol selectivity. These findings provide valuable insights into the efficient production of C 2+ compounds.