Molecularly Tailored Carbon Quantum Dots Enable Enhanced C─C Coupling in CO ₂ Electroreduction

Abstract Selective electroreduction of CO 2 to multi‐carbon products remains a major challenge due to competing hydrogen evolution, weak * CO stabilization, and intrinsic scaling relationships in conventional catalysts. Herein, a quantum dot‐enabled tandem catalyst is introduced, with Cu nanoparticles anchored onto cyano‐functionalized carbon quantum dots (Cu‐CQDs‐CN). Unlike traditional cyano‐modified Cu catalysts, CQDs serve as molecular carriers, enabling precise functionalization, interfacial electric field modulation, and regulated supply of surface * H. This molecular‐level engineering enhances * CO stabilization, promotes * CO─ * CHO coupling, and suppresses hydrogen evolution, thereby driving efficient C 2 H 4 formation. Such Cu‐CQDs‐CN catalyst achieves a Faradaic efficiency of ≈61% for ethylene at a high current density (≈574 mA cm −2 ). Operando spectroscopic analyses and density functional theory calculations reveal that CN functionalization on CQDs optimizes local proton availability and strengthens * CO adsorption, enabling preferential ethylene production. This work establishes a new paradigm of quantum dot‐enabled interfacial engineering for selective CO 2 conversion and offers a generalizable strategy for molecular‐level catalyst design.