Photoactivation of Cu Centers in Metal–Organic Frameworks for Selective CO₂ Conversion to Ethanol

Abstract

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 CO₂ 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 Cu⁰ 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 μmol g_Cu^-1 h^-1 under 2 MPa of H₂/CO₂ = 3:1 at 150 °C. Low-intensity light thus generates and stabilizes Cu^I species for sustained EtOH production.