Copper(II) Frameworks with Varied Active Site Distribution for Modulating Selectivity of Carbon Dioxide...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Metal-organic frameworks (MOFs) show promise as electrocatalysts for CO2 reduction reaction (CO2RR).
• The influence of metal node distribution on CO2RR selectivity in MOFs remains underexplored.

Purpose of the Study:

• To investigate the effect of varying copper(II) site distribution within Cu-MOFs on CO2 electroreduction performance.
• To establish a strategy for modulating CO2RR selectivity by controlling active center distribution in MOFs.

Main Methods:

• Synthesis of three distinct Cu-MOFs ([Cu(L)SO4]·H2O (Cu1), [Cu(L)2(H2O)2](CH3COO)2·H2O (Cu2), and [Cu(L)2(H2O)2](ClO4)2 (Cu3)) using the same ligand but different Cu(II) salts.
• Electrochemical evaluation of CO2 electroreduction, including Faraday efficiency measurements for CO (FE_CO) and H2 (FE_H2).
• Theoretical calculations of Gibbs free energy and electron density to support experimental findings.

Main Results:

• Cu1 exhibited a significantly higher FE_CO (4 times FE_H2), while Cu2 showed a moderate enhancement (2 times FE_H2).
• Cu3 displayed comparable FE_CO and FE_H2, indicating lower selectivity.
• Differences in selectivity are attributed to variations in electrochemical active surface area, charge transfer kinetics, and framework structure influenced by copper site distribution.

Conclusions:

• The distribution of copper(II) sites in Cu-MOFs critically affects CO2RR selectivity.
• Tailoring the distribution of active centers within MOFs provides an effective strategy for enhancing CO2 electroreduction performance and selectivity.