Photoactivation of Cu Centers in Metal—Organic Frameworks for Selective CO_2 Conversion to Ethanol

摘要

ABSTRACT: CO_2 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. Cu1 centers could selectively catalyze CO_2-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_2 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 CO_2 to EtOH with an activity of 9650 μmoI g_(Cu)~(-1) h~(-1) under 2 MPa of H_2/CO_2 = 3:1 at 150 ℃ Low-intensity light thus generates and stabilizes Cu~I species for sustained EtOH production.