Organic-Inorganic Grain Boundary Engineering for Highly Selective and Stable CO₂ Electroreduction to Ethylene

Electrocatalytic conversion of CO₂ to ethylene (C₂H₄), the cornerstone of the chemical industry, offers a sustainable alternative to conventional energy-intensive steam cracking but remains limited by inefficient C-C coupling and competing hydrogen evolution reaction. Here, we report an organic-inorganic grain-boundary (OIGB) catalyst by embedding CuO nanodomains within a Cu-based metal-organic framework matrix, which creates well-defined electronically integrated interfaces that enable cooperative stabilization of *CO and *COH intermediates. The OIGB structure achieves a high Faradaic efficiency of ∼81% for CO₂ electroreduction to C₂H₄ at an industrially relevant current density of 300 mA cm^{- 2}, together with stable operation for over 100 h. Operando spectroscopy combined with computational calculations reveals a synergistic mechanism in which CuO nanodomains serve as local *CO generation sites while Cu-N coordination sites stabilize *COH species, associated with formation of the key *COH-CO intermediate for CO₂ electroreduction to C₂H₄.