We have presented a highly CO-selective, layered imidazolate framework-derived NiNC electrocatalyst (NiNC-IMI) for the efficient electrochemical CO2 reduction to CO in zero-gap single cell electrolyzers. This catalyst exhibited a favorable geometric and mass-based CO activity in liquid-electrolyte H-cells, thanks to its high catalytic active Ni-Nx site density and good site accessibility compared to a polyaniline-derived NiNC-PANI reference catalyst. We associate these favorable properties with its unique mesoporous structure over the microporous characteristics of the NiNC-PANI.