Nanoconfined tandem three-phase photocatalysis for highly selective CO2 reduction to ethanol

The conversion of CO2 and H2O into ethanol with high selectivity via photocatalysis is greatly desired for effective CO2 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 Cu2O shell. The hydrophobic Cu2O shell acts as a CO2 reservoir, effectively overcoming the CO2 mass-transfer limitation, while the Ag core facilitates the conversion of CO2 to CO. Subsequently, CO undergoes continuous reduction within the nanoconfined mesoporous channels of Cu2O. The synergy of enhanced mass transfer, nanoconfinement, and tandem reaction leads to elevated *CO concentrations and prolonged interaction time within the Cu2O 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 C2+ compounds.