• • RC-COF-1@Cu electrode achieves a maximum C2+ Faradaic efficiency of 67.0% at 500 mA cm−2 in acidic electrolyte, demonstrating industrially relevant performance for multicarbon production.
• • The electrode maintains a total carbon product Faradaic efficiency above 90% across a wide current density range (100–500 mA cm−2), indicating stable selectivity under varying operational conditions.
• • CO diffusion coefficient within RC-COF-1 is 3.07 Å2 ps−1, significantly lower than 10.31 Å2 ps−1 in RC-COF-3, confirming enhanced confinement of CO intermediates that promotes C-C coupling.
• • The dual-confinement effect of CO2 and *CO, achieved through pore engineering, effectively suppresses hydrogen evolution and monocarbon formation, offering a design strategy for selective CO2 electrolysis.