A Confined Cu _x O@Styrene Microreactor Achieves the Conversion of CO ₂ to C ₂₊ Products via Intermediate Trapping

ABSTRACT The electrochemical reduction of carbon dioxide to multi‐carbon (C ₂₊ ) products is impeded by the instability and inefficient utilization of key reaction intermediates. To address this challenge, we developed a strategy based on geometric control of spatially confined microenvironments, enabling the rational design of programmable Cu _x O microreactors on Cu ²⁺ (111)/Cu ⁺ (200) substrates. Two distinct catalyst architectures—small‐ordered (s‐Cu _x O@styrene) and large‐ordered (c‐Cu _x O@styrene)—were systematically engineered to modulate CO intermediate behavior, thereby directing reaction selectivity toward ethylene and ethanol production. Faradaic efficiencies for C ₂₊ products demonstrate pronounced dependence on microstructure: increasing from negligible values in the small‐ordered s‐Cu _x O@styrene (25.6% ethylene,12.4% ethanol, 3% propylene) to 78.8% in the large‐ordered c‐Cu _x O@styrene (55% ethylene, 23% ethanol, 1% propylene). In situ infrared spectroscopy reveals that the highly ordered configuration enhances CO adsorption, promoting the accumulation of critical *OCCOH and *OC ₂ H ₅ intermediates. Moreover, synergistic interactions between Cu ⁺ and Cu ⁰ active sites accelerate C–C coupling kinetics, favoring selective formation of C ₂₊ species. This work establishes a geometry‐driven paradigm for controlling catalytic selectivity independent of compositional tuning, offering a promising avenue for the development of adaptive catalytic systems in renewable energy conversion.