A Two-Dimensional van der Waals Heterostructure with Isolated Electron-Deficient Cobalt Sites toward High-Efficiency CO 2 Electroreduction.

Electrochemical CO 2 conversion is a promising way for sustainable chemical fuel production, yet the conversion efficiency is strongly limited by the sluggish kinetics and complex reaction pathways. Here we report the ultrathin conjugated metalloporphyrin covalent organic framework epitaxially grown on graphene as a two-dimensional van der Waals heterostructure to catalyze CO 2 reduction. Operando X-ray absorption and density functional theory calculations reveal the strong interlayer coupling leads to electron-deficient metal centers and speeds up electrocatalysis. The Co(III)-N 4 centers exhibit a CO Faradaic efficiency of 97% at a partial current density of 8.2 mA cm -2 in an H-cell, along with a stable running over 30 h. The selectivity of CO approached 99% with a partial current density of 191 mA cm -2 in a liquid flow cell, and the turnover frequency achieved 50 400 h -1 at -1.15 V vs RHE, outperforming most reported organometallic frameworks. This work highlights the key role of strong electronic coupling between van der Waals layers for accelerating the dynamics of CO 2 conversion.