Carbon capture is considered a critical means for climate change mitigation. However, conventional wet chemical scrubbing utilizing sp³ amines suffers from high energy consumption, corrosion and sorbent degradation, motivating the search for more efficient carbon dioxide separation strategies. Here, we demonstrate a library of redox-tunable Lewis bases with sp²-nitrogen centres that can reversibly capture and release carbon dioxide through an electrochemical cycle. The mechanism of the carbon capture process is elucidated via a combined experimental and computational approach. We show that the properties of these Lewis base sorbents can be fine-tuned via molecular design and electrolyte engineering. Moreover, we identify a bifunctional azopyridine base that holds promise for electrochemically mediated carbon capture, exhibiting >85% capacity utilization efficiency over cycling in a flow system under 15% carbon dioxide with 5% oxygen. This work broadens the structural scope of redox-active carbon dioxide sorbents and provides design guidelines on molecules with tunable basicity under electrochemical conditions.