Ultrafine Cu nanoclusters confined within covalent organic frameworks for efficient electroreduction of CO2 to CH4 by synergistic strategy

Electrocatalytic CO2 reduction (ECR) to high value-added chemicals by using renewable electricity presents a promising strategy to realize "carbon neutrality". However, the ECR system is still limited by its low current density and poor CO2 utilization efficiency. Herein, by using the confinement effect of covalent organic frameworks (COFs) to confine the in-situ growth of metal nanoclusters (NCs), we develop a series of Cu NCs encapsulated on COF catalysts (Cu-NC@COF) for ECR. Among them, Cu-NC@CuPc-COF as a gas diffusion electrode (GDE) achieves a maximum CO2-to-CH4 Faradaic efficiency of 74 +/- 3% (at -1.0 V vs. Reversible Hydrogen Electrode (RHE)) with a current density of 538 +/- 31 mA cm-2 (at -1.2 V vs. RHE) in a flow cell, making it one of the best among reported materials. More importantly, the current density is much higher than the relevant industrial current density (200 mA cm-2), indicating the potential for industrial application. This work opens up new possibilities for the design of ECR catalysts that utilize synergistic strategy.