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

Since the 20th century, massive CO 2 emissions from fossil fuel combustion have intensified the global climate crisis. The efficient conversion of CO 2 into high-value multicarbon (C 2+ ) products represents a central challenge for energy system transformation. Among various technologies, electrocatalytic CO 2 reduction (CO 2 RR) 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 CO 2 in aqueous electrolytes, yet they suffer from insufficient selectivity and stability. This review systematically examines the advanced strategy of optimizing copper-based CO 2 RR 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, C 2+ 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 CO 2 conversion technologies.