Steering CO2 Electroreduction to Methane and Deuterated Methane via Hydrogen-Bond Engineering on Copper-Phenolic Networks.
Electrochemical CO2 reduction (eCO2R) powered by renewable electricity offers a sustainable route for carbon cycling and value-added chemical synthesis. Among possible products, methane (CH4) is particularly attractive due to its high energy density and direct compatibility with existing natural gas infrastructure. However, it remains challenging to selectively produce CH4 with conventional copper catalysts. Herein, we developed a copper-phenolic network catalyst featuring atomically dispersed Cu─O4 sites, where adjacent uncoordinated hydroxyl groups from tannic acid (TA) act as intrinsic hydrogen-bond donors to stabilize the oxygen-bound formate intermediate (*OCHO). This hydrogen-bond-enabled microenvironment redirects eCO2R from the conventional *CO-mediated pathway toward a formate-derived route, while simultaneously suppressing the competing hydrogen evolution reaction. As a result, the optimized Cu-PTA catalyst delivers a high CH4 Faradaic efficiency of 75.5% with a partial current density of 302.0 mA cm-2 in aqueous electrolyte. Notably, this pathway-steering strategy is readily applicable to deuterated electrolytes, enabling efficient production of deuterated methane (CD4) with a record-high Faradaic efficiency of 83.1% and a partial current density of 415.6 mA cm-2. This work establishes hydrogen-bond engineering as a general approach for manipulating reaction pathways through local stabilization of oxygen-bound intermediates toward sustainable synthesis of high-value chemicals.