posted on 2023-11-10, 10:20authored byJaya Bharti, Lingjing Chen, Zhenguo Guo, Lin Cheng, Joël Wellauer, Oliver S. Wenger, Niklas von Wolff, Kai-Chung Lau, Tai-Chu Lau, Gui Chen, Marc Robert
Visible-light-driven reduction of CO2 to both
CO and
formate (HCOO–) was achieved in acetonitrile solutions
using a homobimetallic Cu bisquaterpyridine complex. In the presence
of a weak acid (water) as coreactant, the reaction rate was enhanced,
and a total of ca. 766 TON (turnover number) was reached for the CO2 reduction, with 60% selectivity for formate and 28% selectivity
for CO, using Ru(phen)32+ as a sensitizer and
amines as sacrificial electron donors. Mechanistic studies revealed
that with the help of cooperativity between two Cu centers, a bridging
hydride is generated in the presence of a proton source (water) and
further reacts with CO2 to give HCOO–. A second product, CO, was also produced in a parallel competitive
pathway upon direct coordination of CO2 to the reduced
complex. Mechanistic studies further allowed comparison of the observed
reactivity to the monometallic Cu quaterpyridine complex, which only
produced CO, and to the related homobimetallic Co bisquaterpyridine
complex, that has been previously shown to generate formate following
a mechanism not involving the formation of an intermediate hydride
species.