Confinement Effect-Engineered Cu-Based Catalysts: Mechanisms and Performance in Electrocatalytic CO ₂ Reduction

Since the 20th century, massive CO2 emissions from fossil fuel combustion have intensified the global climate crisis. The efficient conversion of CO2 into high-value multicarbon (C2+) products represents a central challenge for energy system transformation. Among various technologies, electrocatalytic CO2 reduction (CO2RR) is recognized as the most promising route due to its tunable pathways and compatibility with renewable energy. Copper-based materials stand out as the only metal catalysts capable of selectively producing hydrocarbons and oxygenate from CO2 in aqueous electrolytes, yet they suffer from insufficient selectivity and stability. This review systematically examines the advanced strategy of optimizing copper-based CO2RR catalysts through confinement effect engineering. Distinct from prior perspectives treating confinement as a secondary feature, this work establishes it as a primary design principle, which creates tailored microenvironments enabling synergistic spatial constriction and electronic regulation to precisely steer reaction pathways. A comprehensive summary is provided on diverse catalyst architectures constructed via confinement engineering (e.g., core–shell assemblies, porous frameworks, and nanocavities), with an in-depth discussion of the fundamental mechanisms─including intermediate enrichment, electronic structure modulation, and dynamic stability reinforcement, which underpin the enhanced activity, C2+ selectivity, and durability. Current challenges regarding the dynamic evolution of confined microenvironments and industrial scalability are outlined. Future research directions involving cross-scale design, integrated characterization modeling, and process innovation are proposed. This review aims to provide a robust theoretical foundation and clear technical pathway for designing highly efficient and stable confined catalytic systems, thereby accelerating the practical implementation of CO2 conversion technologies.