Neutral Electrosynthesis of Methane from Diluted CO₂ on Dense Cu Sites Embedded Covalent Organic Frameworks

Electrochemical upgrading of diluted CO₂, particularly in neutral media, offers a promising route to reduce the costs associated with purified/concentrated CO₂ streams. However, challenges, such as sluggish mass transport, competitive hydrogen evolution, and poor selectivity, remain unresolved. Herein, we design a covalent organic framework (COF) featuring dense (8.4 wt %) copper atomic sites (Cu-COFs) for boosting direct electroreduction of diluted CO₂ to methane. We demonstrate that the pyridinic N and microporous structure of Cu-COFs efficiently enrich local CO₂ through dominant van der Waals force and nano confinement, while the pyridinic nitrogen functional groups from Cu-COFs facilitate the formation of electron-deficient copper sites. In situ spectroscopic analysis and density functional theory calculations further reveal that the copper atomic sites can facilitate *CO adsorption, promote water dissociation, and suppress *CO dimerization, thereby selectively steering the reaction pathway toward methane. Benefiting from its tailored mass and charge transfer, the as-made Cu-COFs catalyst achieves a peak CH₄ Faradaic efficiency (FE) of 79.1% in 60 vol % CO₂ and maintains 61.1% even in a simulated flue gas (CO₂/N₂ = 15:85, v/v), representing a record for methane electrosynthesis under low CO₂ concentrations. This coupling engineering of mass transport and catalytic sites opens a strategic pathway for the direct utilization of industrially dilute CO₂ streams.