Photo- and Electrocatalytic Reduction of CO2 over Metal–Organic Frameworks and Their Derived Oxides: A
Correlation of the Reaction Mechanism with the Electronic Structure
posted on 2022-01-27, 20:03authored bySoumitra Payra, Subhasmita Ray, Ruchi Sharma, Kartick Tarafder, Paritosh Mohanty, Sounak Roy
A Ce/Ti-based bimetallic 2-aminoterephthalate
metal–organic
framework (MOF) was synthesized and evaluated for photocatalytic reduction
of CO2 in comparison with an isoreticular pristine monometallic
Ce-terephthalate MOF. Owing to highly selective CO2 adsorption
capability, optimized band gaps, higher flux of photogenerated electron–hole
pairs, and a lower rate of recombination, this material exhibited
better photocatalytic reduction of CO2 and lower hydrogen
evolution compared to Ce-terephthalate. Thorough probing of the surface
and electronic structure inferred that the reducibility of Ce4+ to Ce3+ was due to the introduction of an amine
functional group into the linker, and low-lying Ti(3d) orbitals in Ce/Ti-2-aminoterephthalate facilitated the photoreduction
reaction. Both the MOFs were calcined to their respective oxides of
Ce1–xTixO2 and CeO2, and the electrocatalytic reduction
of CO2 was performed over the oxidic materials. In contrast
to the photocatalytic reaction mechanism, the lattice substitution
of Ti in the CeO2 fluorite cubic structure showed a better
hydrogen evolution reaction and consequently, poorer electroreduction
of CO2 compared to pristine CeO2. Density functional
theory calculations of the competitive hydrogen evolution reaction
on the MOF and the oxide surfaces corroborated the experimental findings.