This study introduces the use of nanosized metal-organic frameworks (MOFs) as efficient and selective catalysts for the electrocatalytic reduction of carbon dioxide (CO2) to carbon monoxide (CO) in aqueous electrolytes. The authors focus on a cobalt-porphyrin MOF, Al3(OH)2TCPP-Co, which exhibits a high selectivity for CO production (over 76%) and stability over 7 hours with a per-site turnover number (TON) of 1400. In situ spectroelectrochemical measurements reveal that the cobalt oxidation state changes from Co(II) to Co(I) during the catalytic process, indicating the redox-accessibility of the catalytic centers. The MOF's modular nature allows for the functionalization and modification of its organic and inorganic components, making it a promising platform for the development of advanced electrocatalysts for CO2 reduction. The study highlights the potential of MOFs in balancing charge and mass transport, achieving high catalytic efficiency, and maintaining long-term stability.This study introduces the use of nanosized metal-organic frameworks (MOFs) as efficient and selective catalysts for the electrocatalytic reduction of carbon dioxide (CO2) to carbon monoxide (CO) in aqueous electrolytes. The authors focus on a cobalt-porphyrin MOF, Al3(OH)2TCPP-Co, which exhibits a high selectivity for CO production (over 76%) and stability over 7 hours with a per-site turnover number (TON) of 1400. In situ spectroelectrochemical measurements reveal that the cobalt oxidation state changes from Co(II) to Co(I) during the catalytic process, indicating the redox-accessibility of the catalytic centers. The MOF's modular nature allows for the functionalization and modification of its organic and inorganic components, making it a promising platform for the development of advanced electrocatalysts for CO2 reduction. The study highlights the potential of MOFs in balancing charge and mass transport, achieving high catalytic efficiency, and maintaining long-term stability.