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

The conversion of CO and HO into ethanol with high selectivity photocatalysis is greatly desired for effective CO 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 CuO shell. The hydrophobic CuO shell acts as a CO reservoir, effectively overcoming the CO mass-transfer limitation, while the Ag core facilitates the conversion of CO to CO. Subsequently, CO undergoes continuous reduction within the nanoconfined mesoporous channels of CuO. The synergy of enhanced mass transfer, nanoconfinement, and tandem reaction leads to elevated *CO concentrations and prolonged interaction time within the CuO 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 compounds.