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[Display omitted] • Highly exposed isolated FeN 5 sites are embedded in N-doped carbon frameworks. • FeN 5 exhibits a maximum FE CO of 98% and over 95% from −0.4 to −1.0 V vs. RHE. • The axial coordinated N modulates the d -band center and facilitates CO desorption. • FeN 4 and axial coordinated N act synergistically to boost CO 2 -to-CO conversion. Electrochemical CO 2 conversion offers a sustainable approach to alleviate the energy crisis but remains a long-standing challenge. Herein, atomically dispersed FeN 5 sites anchored on N-doped carbon matrix templated by zeolitic imidazole framework-8 (ZIF-8) are facilely synthesized for efficient catalyzing CO 2 reduction. The FeN 5 single-atom catalyst (Fe-SA/ZIF) presents the Faradaic efficiency of 98% at −0.7 V vs. RHE and over 95% in a wide potential range from −0.4 to −1.0 V vs. RHE, surpassing most of the reported single-atom catalysts for CO 2 RR. Further density functional theory (DFT) calculations reveal that the outstanding activity of FeN 5 sites mainly originates from the lowered d -band center modulated by the out-of-plane coordinated pyridinic N, which reduces the CO adsorption energy from −1.71 to −1.49 eV compared to FeN 4 moieties. Thus, the synergistic effect between FeN 4 sites and the coordinated pyridine offers new insight in designing outstanding electrocatalysts for multiple applications. [ABSTRACT FROM AUTHOR]