Coordination‐Engineered Interfacial Pathway Partitioning for Electrocatalytic CO ₂ Conversion and Downstream Upgrading

Electrochemical CO 2 reduction (eCO 2 RR) is increasingly capable of delivering downstream‐compatible carbon products, yet the interfacial origin of pathway selection remains insufficiently understood. Here, coordination‐environment‐tunable Cu–Sn catalysts are employed to partition CO 2 electrosynthesis between a Sn‐centered formate‐selective pathway and a Cu‐centered CO‐selective pathway. In situ spectroscopy reveals coordination‐dependent evolution of adsorbed intermediate and interfacial water structures, while H/D kinetic isotope analysis and in situ electrochemical impedance spectroscopy‐distribution of relaxation times (EIS‐DRT) measurements resolve distinct proton‐coupled and polarization‐sensitive kinetic regimes. Density functional theory calculations further elucidate the energetic origin of pathway bifurcation through coordination‐dependent reconstruction of adsorption geometry and interfacial energetics. Sn‐centered medium‐coordination regimes favor oxygen‐bound intermediates and a proton‐coupled formate pathway, whereas Cu‐centered medium‐coordination regimes promote carbon‐bound adsorption and CO‐selective reactivity. In the downstream modules, electrodialysis achieves a 98.1% HCOOK‐to‐HCOOH conversion with 93.97% Faradaic efficiency (FE) at 300 mA cm −2 , while CO 2 ‐NH 3 route delivers formamide with a maximum FE of 45.2% and a production rate of 840 µmol cm −2 h −1 . This work establishes coordination‐engineered interfacial partitioning as a strategy for integrated CO 2 electrosynthesis with downstream upgrading.