Multi-timescale transformations in MOF-modified copper oxide during electrochemical CO2 reduction

Metal-organic frameworks (MOFs) have received increased interest towards developing an improved local microenvironment for the electrochemical CO 2 reduction reaction (CO 2 RR). However, for many MOFs, little is known about the actual structure of the active catalytic sites during the reaction due to the dynamic restructuring of MOF-based electrocatalysts. Here, a Cu-MOF (HKUST-1) was synthesized directly on CuO nanosheets as a model system to elucidate multiple concurrent time-dependent restructuring processes to reveal the nature of nanoscale active site transformations and selectivity changes during CO 2 RR. While the CuO nanosheets are gradually reduced to oxide-derived Cu nanosheets, the HKUST-1 Cu-MOF quickly reorganizes within 60 s, forming abundant coordinated COO-Cu complexes. Over longer timescales, both oxide-derived and non-oxide-derived Cu particles form, which affects the ratio between CH 4 formation and C-C coupling to C 2 H 4 . This investigation of these multi-timescale transformations offers new insights that inform the development of MOF-derived and stable MOF electrocatalysts for CO 2 RR.