Electrochemical CO₂ conversion to methane requires a multi-step hydrogenation and involves a complex cascade reaction. It would be vital to achieve efficient catalytic performance if one could construct tandem active centers towards the multiple intermediates. Herein, we provided a pyrolysis-free synthetic strategy to fabricate monoatomic-nanocluster Cu dual active centers for highly selective methanation of CO₂. Expectedly, the tandem active centers realized the stepwise electrocatalytic reduction, during which the atomic Cu increased the dissociation of H₂O while the Cu nanoclusters with a high electron density promoted the activation of CO₂, synergistically accelerating the hydrogenation of *CO into *CHO, suppressing H₂ generation and favoring the formation of CH₄. The as-prepared catalysts demonstrated a superior Faradaic efficiency of 78.8% with a large partial CH₄ current density of 111.5 mA·cm⁻² at −1.3 V vs. RHE, providing an avenue for the rational design and controllable synthesis of highly selective and active Cu-based CO₂ reduction reaction (CO₂RR) catalysts.

The lower electricity consumption (EC) and higher value-added products are much desired yet still challenging for the development of CO₂ coupling electrocatalytic systems. Herein, we give insight into the inherent nature of the retrenchment of EC by exploring the photo-assisted co-electrolysis of methanol and CO₂ system using a kind of hydroxyl-rich covalent organic frameworks (Dha-COF-Co) with well-tuned pore structure and morphology. Specifically, the hydroxyl induced hydrogen bond interaction in Dha-COF-Co enables to simultaneously regulate the pore microenvironment and nanoribbon morphology of COFs for performance boosting. Notably, the obtained Dha-COF-Co nanoribbon exhibits an overall EC retrenchment of ~41.2% (highest in porous crystalline materials to date) when replacing the anodic OER with MOR in the photo-electrocatalytic MOR-CO₂RR coupling system, as well as superior FE_HCOOH (anode, ~100%) and FE_CO (cathode, >95%) at 1.8 V. Combined theoretical calculations with various characterizations, the vital role of hydroxyl group in both microenvironment and morphology tuning that can facilitate the CO₂RR and MOR kinetics to retrench the EC has been intensively discussed.