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

Metal-organic frameworks (MOFs) can be utilized as electrocatalysts for CO 2 reduction reaction (CO 2 RR) due to their well dispersed metal centers. However, the influence of metal node distribution on electrochemical CO 2 RR was rarely explored. Here, three Cu-MOFs with different copper(II) site distribution were employed for CO 2 electroreduction. The Cu-MOFs [Cu(L)SO 4 ]·H 2 O ( Cu1 ), [Cu(L) 2 (H 2 O) 2 ](CH 3 COO) 2 ·H 2 O ( Cu2 ), and [Cu(L) 2 (H 2 O) 2 ](ClO 4 ) 2 ( Cu3 ) were achieved by using the same ligand 1,3,5-tris(1-imidazolyl)benzene (L) but different Cu(II) salts. The results show that the Faraday efficiency of CO (FE CO ) for Cu1 is 4 times that of the FE H2 , while the FE CO of Cu2 is twice that of the FE H2 . As for Cu3 , there is not much difference between FE CO and FE H2 . Such difference may arise from the distinct electrochemical active surface area and charge transfer kinetics caused by different copper site distribution. Furthermore, the different framework structures also affect the activity of the copper sites, which was supported by the theoretically calculated Gibbs free energy and electron density, contributing to the selectivity of CO 2 RR. This study provides a strategy for modulating the selectivity of CO 2 RR by tuning the distribution of the active centers in MOFs.