Transition Metals on Fluorine-Containing Graphyne with Tunable Hydrophobicity for Effective CO₂ Reduction

Transition metal catalysts supported on carbon materials play pivotal roles in various catalytic reactions. Tailoring the chemical structures of supporting carbon materials is an effective way for fine-tuning the microenvironment and thereby the catalytic properties of the metal sites; however, achieving precise control remains challenging. Herein, an aromatic nucleophilic substitution strategy is employed to synthesize a series of fluorographynes (F-GYs), enabling adjustable fluorine contents to manipulate surface wettability. While the increased fluorine content induces minor structural compromises, the as-prepared F-GYs still retain the characteristic sp-sp² conjugated network, making them suitable for supporting single-atom (SA) and nanocluster (NC) metals (Co, Ni, Cu, Pd, Rh and Ag). In a proof-of-concept demonstration, SA Cu on the high-fluorine-content F-GY support proves more conducive to the electrochemical CO₂-to-CH₄ production due to the active site's SA nature and hydrophobic microenvironment, achieving optimum faradaic efficiency of 76.3% for CH₄ production. In situ electrochemical Raman spectroscopy study reveals that covalent C-F groups of F-GY inhibit the activity of water diffusion at the electrified interface, creating a highly hydrophobic microenvironment favorable for electrochemical CO₂ methanation. This work highlights a novel approach for designing catalysts with tunable microenvironments in hydrophobicity, offering a versatile platform for enhancing CO₂RR selectivity and efficiency through precise surface modification.