Mechanisms and challenges of nanoporous confinement for carbon dioxide electrocatalysis

The carbon dioxide reduction reaction (CO₂RR) is a promising strategy for converting CO₂ into high-value chemicals. However, the rational design of efficient catalysts for steering product selectivity toward specific high-value chemicals continues to be a central goal in electrocatalysis research. Recently, nanoporous confined electrocatalysts have garnered attention due to their unique pore structures, which not only increase the accessibility and utilization of active sites but also promote the enrichment and stabilization of key reaction intermediates and modulate the local reaction microenvironment. These combined effects contribute to improved reaction kinetics and enhanced product selectivity. This review systematically summarizes the mechanistic foundations of nanoporous confinement in CO₂RR, emphasizing its role in governing reaction pathways and selectivity. We introduce the fundamental design principles of nanoporous confined electrocatalysts, detailing how their pore size, tortuosity, connectivity influence CO₂ diffusion, local concentration gradients, and electrolyte accessibility. Then highlight how confinement-induced spatial regulation facilitates intermediate accumulation, directional proton transfer, and local pH modulation, collectively steering product selectivity toward desired C₁ and multi-carbon (C₂₊) products. Representative material systems and structure-performance relationships are discussed to illustrate these effects. Finally, we summarize the current challenges in mechanistic understanding and practical implementation, and propose future directions for developing nanoporous systems that integrate controlled transport, catalytic reactivity, and system-level scalability.