Local Weak Hydrogen Bonds Significantly Enhance CO2 Electroreduction Performances of a Metal-Organic Framework

Technological application of the electrochemical reduction of CO2 relies on efficient electrocatalysts. We demonstrate that the introduction of amino groups alongside the porphyrin cobalt centers in a metal-organic framework (MOF) can dramatically accelerate the electrochemical CO2 reduction performance. A classic cobalt porphyrin-based MOF showing moderate CO2-to-CO electroreduction performance (turnover frequency [TOF] = 0.20 s-1, Faradic efficiency [FE] = 47.4%) is modified. By molecular design of the porphyrin-based ligand, amino groups are introduced alongside the cobalt center, giving remarkably enhanced CO2-to-CO electroreduction performance as high as FE 99.4%, current density 7.2 mA cm-2, and TOF 21.17 s-1, in a near neutral aqueous solution at a low overpotential of 525 mV. Density functional theory calculations showed that the prepositioned amino groups, although located not sufficiently close to the active center, serve as hydrogen-bonding donors to stabilize the intermediate Co-CO2 adduct and impede the formation of Co-H2O adduct, which not only promotes the CO2 reduction reaction but also restrains the hydrogen evolution reaction.

Automated summary

The electrochemical reduction of CO2 can be significantly improved by introducing amino groups alongside porphyrin cobalt centers in a metal-organic framework (MOF).