Designing catalysts with highly active, selectivity, and stability for electrocatalytic CO₂ to formate is currently a severe challenge. Herein, we developed an electronic structure engineering on carbon nano frameworks embedded with nitrogen and sulfur asymmetrically dual-coordinated indium active sites toward the efficient electrocatalytic CO₂ reduction reaction. As expected, atomically dispersed In-based catalysts with In-S₁N₃ atomic interface with asymmetrically coordinated exhibited high efficiency for CO₂ reduction reaction (CO₂RR) to formate. It achieved a maximum Faradaic efficiency (FE) of 94.3% towards formate generation at −0.8 V vs. reversible hydrogen electrode (RHE), outperforming that of catalysts with In-S₂N₂ and In-N₄ atomic interface. And at a potential of −1.10 V vs. RHE, In-S₁N₃ achieves an impressive Faradaic efficiency of 93.7% in flow cell. The catalytic performance of In-S₁N₃ sites was confirmed to be enhanced through in-situ X-ray absorption near-edge structure (XANES) measurements under electrochemical conditions. Our discovery provides the guidance for performance regulation of main group metal catalysts toward CO₂RR at atomic scale.