A key challenge in electrochemical carbon dioxide reduction is designing catalytic materials with high product selectivity, stability, and earth-abundant composition. This study introduces thin films of nanosized metal-organic frameworks (MOFs) as efficient and selective catalysts for CO₂ reduction to CO in aqueous electrolytes. A cobalt-porphyrin MOF, Al₂(OH)₂TCPP-Co(TCPP-H₂=4,4',4'',4'''-porphyrin-5,10,15,20-tetrayl)tetrabenzoate, showed 76% CO selectivity and a turnover number (TON) of 1400 over 7 hours. In situ spectroelectrochemical measurements revealed that most catalytic centers are redox-accessible, with Co(II) reduced to Co(I) during catalysis. The MOF catalyst demonstrated high performance, stability, and selectivity, making it a promising candidate for further development in electrocatalytic CO₂ reduction. The study highlights the potential of MOFs as modular catalysts, with their organic and inorganic components functionalized for tailored catalytic properties. The MOF-based system integrates catalytic molecular units into a porous network, maximizing active sites and balancing charge and mass transport. The catalyst was tested over extended periods, showing stable performance and retaining crystallinity after electrolysis. The study also provides insights into the redox behavior of the cobalt centers and the mechanism of CO₂ reduction. The results demonstrate the effectiveness of MOFs in electrochemical CO₂ reduction, offering a new approach for sustainable energy conversion.A key challenge in electrochemical carbon dioxide reduction is designing catalytic materials with high product selectivity, stability, and earth-abundant composition. This study introduces thin films of nanosized metal-organic frameworks (MOFs) as efficient and selective catalysts for CO₂ reduction to CO in aqueous electrolytes. A cobalt-porphyrin MOF, Al₂(OH)₂TCPP-Co(TCPP-H₂=4,4',4'',4'''-porphyrin-5,10,15,20-tetrayl)tetrabenzoate, showed 76% CO selectivity and a turnover number (TON) of 1400 over 7 hours. In situ spectroelectrochemical measurements revealed that most catalytic centers are redox-accessible, with Co(II) reduced to Co(I) during catalysis. The MOF catalyst demonstrated high performance, stability, and selectivity, making it a promising candidate for further development in electrocatalytic CO₂ reduction. The study highlights the potential of MOFs as modular catalysts, with their organic and inorganic components functionalized for tailored catalytic properties. The MOF-based system integrates catalytic molecular units into a porous network, maximizing active sites and balancing charge and mass transport. The catalyst was tested over extended periods, showing stable performance and retaining crystallinity after electrolysis. The study also provides insights into the redox behavior of the cobalt centers and the mechanism of CO₂ reduction. The results demonstrate the effectiveness of MOFs in electrochemical CO₂ reduction, offering a new approach for sustainable energy conversion.