Tuning diffusion modes in micropore reactors enables efficient gas-liquid transport for CO₂ electroreduction

Porous materials are widely used in electrochemical CO₂ reduction for the desired spatial confinement effect. While the porous channels could hinder the overall performance by limiting the mass transfer process, especially when the pore size reaches nanometer scale. Herein, we demonstrated that such transport-confinement trade-off could be overcame by decorating the channel with O-coordinating species. Specifically, Cu nanoparticles are encapsulated in a microporous reactors as active centers and introduce highly dispersed Fe clusters to perturb the migration constraint of one-dimensional single-file water via strong O-coordination, substantially enhancing CO₂ mass-transport flux toward the micropore interior. Fe-sites trap water molecules via strong metal-O coordination, which disrupts the hydrogen bonding and van der Waals force networks of single-file water along the pore walls, reduces the resistance for oriented water diffusion inside micropores and alleviates stagnation-derived hindrance to CO₂ migration. Consequently, a continuous gas–liquid synergistic transport pathway driven by the Fe sites is established within the micropores. The Cu_3.9-Fe_cluster/NC catalyst delivers a CO FE of ∼ 93.7% at pH ∼ 7 and −0.6 V_RHE. At pH ∼ 1, the CO selectivity approaches 100% across a current density range of 50–150  mA cm⁻², with stable operation exceeding 18 h. At 200 mA cm⁻², the SPCE reaches 70%. This work demonstrates that introducing functional sites into confined systems to engineer solid–liquid interfacial interactions can reconstruct molecular transport hindrance in confined spaces, overcome diffusion limitations of sub-nanometer micropores, and enable synergistic optimization of reactant transport and catalytic kinetics.