<p>Electrochemical CO₂ conversion has the potential to offer a transformative approach in green chemistry, enabling sustainable production of high-value chemical feedstocks while advancing carbon-neutral initiatives. However, finding a robust electrocatalyst that selectively reduces CO₂ at low concentrations remains a notable challenge because mass transport constraints severely hinder CO₂ conversion at elevated current densities. Here we show an azobenzene-derived coordination-polymer assembly with a single-site nickel phthalocyanine catalyst for low-concentration CO₂ capture and electrolysis at industrially relevant current densities. The assembly, upon electrochemical reduction, provides hydrogen-bond donors for selective CO₂ capture, thereby enhancing the local CO₂ concentration for accelerated electrolysis kinetics. Using a dilute CO₂ (15%) feed stream, the assembled catalyst demonstrates remarkable electrocatalytic performance with a CO partial current density of 435 mA cm⁻². Diffusion limitation in large-scale CO₂ electrolysers is mitigated to support a scaled-up membrane electrode assembly (100 cm²) for CO production at a partial current of 85 A.</p><p></p>