CO2 hydrogenation to ethanol is of practical importance but poses a significant challenge due to the need of forming one C-C bond while keeping one C-O bond intact. Cu-I centers could selectively catalyze CO2-to-ethanol conversion, but the Cu-I catalytic sites were unstable under reaction conditions. Here we report the use of low-intensity light to generate Cu-I species in the cavities of a metal-organic framework (MOF) for catalytic CO, hydrogenation to ethanol. X-ray photoelectron and transient absorption spectroscopies indicate the generation of Cu-I species via single-electron transfer from photoexcited [Ru(bpy)(3)](2+)-based ligands on the MOF to Cu-II centers in the cavities and from Cu-0 centers to the photoexcited [Ru(bpy)(3)](2+)-based ligands. Upon light activation, this Cu-Ru-MOF hybrid selectively hydrogenates CO2 to EtOH with an activity of 9650 mu mol g(cu)(-1) h(-1) under 2 MPa of H-2/CO2 = 3:1 at 150 degrees C. Low-intensity light thus generates and stabilizes Cu-I species for sustained EtOH production.