Scalable Synthesis and Electrocatalytic Performance of Highly Fluorinated Covalent Organic Frameworks for Oxygen Reduction

• Published in: Angewandte Chemie Vol. 135; no. 47
• Main Authors: Martínez‐Fernández, Marcos, Martínez‐Periñán, Emiliano, Peña Ruigómez, Alejandro, Cabrera‐Trujillo, Jorge J., Navarro, Jorge A. R., Aguilar‐Galindo, Fernando, Rodríguez‐San‐Miguel, David, Ramos, Mar, Vismara, Rebecca, Zamora, Félix, Lorenzo, Encarnación, Segura, José L.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 20.11.2023
• Subjects: Additives; Chemical reduction; Chemistry; COF; Electrocatalysis; Electrocatalysts; Fluorination; Fluorine; Frameworks; H2O2; Hydrogen peroxide; Hydrophobicity; Interlayers; Mathematical analysis; ORR; Oxygen reduction reactions; Reaction mechanisms; Synthesis
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202313940

In this study, we present a novel approach for the synthesis of covalent organic frameworks (COFs) that overcomes the common limitations of non‐scalable solvothermal procedures. Our method allows for the room‐temperature and scalable synthesis of a highly fluorinated DFTAPB‐TFTA‐COF, which exhibits intrinsic hydrophobicity. We used DFT‐based calculations to elucidate the role of the fluorine atoms in enhancing the crystallinity of the material through corrugation effects, resulting in maximized interlayer interactions, as disclosed both from PXRD structural resolution and theoretical simulations. We further investigated the electrocatalytic properties of this material towards the oxygen reduction reaction (ORR). Our results show that the fluorinated COF produces hydrogen peroxide selectively with low overpotential (0.062 V) and high turnover frequency (0.0757 s−1) without the addition of any conductive additives. These values are among the best reported for non‐pyrolyzed and metal‐free electrocatalysts. Finally, we employed DFT‐based calculations to analyse the reaction mechanism, highlighting the crucial role of the fluorine atom in the active site assembly. Our findings shed light on the potential of fluorinated COFs as promising electrocatalysts for the ORR, as well as their potential applications in other fields. Covalent organic frameworks (COFs) are a class of crystalline polymers. Herein we report the room temperature and scalable synthesis of two isostructural COFs, modulated by the introduction of fluorine atoms, obtaining an extended framework with record number of F per pore. The substitution produces a dramatical increase of selectivity for the oxygen reduction reaction electrocatalysis, with a response comparable to other noble electrocatalysts.