Cationic Microenvironment Enhancing Covalent Organic Frameworks for Electrocatalytic CO ₂ to CH ₄ Conversion

Abstract

ABSTRACT Electrocatalytic reduction of CO 2 to CH 4 is hindered by sluggish proton‐coupled electron transfer kinetics and competing reaction pathways. Herein, we introduce a cationic microenvironment strategy that integrates reactant enrichment, proton regulation, and intermediate stabilization within a single framework. A tetra‐alkylammonium cation‐functionalized copper porphyrin covalent organic framework (Cu‐Tph‐COF‐N + ) achieves a CH 4 Faradaic efficiency of 66.8% at −1.2 V versus RHE, together with markedly enhanced turnover frequency and partial current density relative to its hydroxyl‐functionalized analogue. Mechanistically, the cationic framework generates a localized electrostatic field that concentrates CO 2 near active sites through charge‐dipole interactions while cooperatively interacting with hydrated K + ions to modulate proton transfer, thereby suppressing hydrogen evolution without compromising proton availability. The resulting electronic modulation at Cu porphyrin stabilizes key *COOH and *CHO intermediates and facilitates C–H bond formation, as supported by theoretical calculations and in situ spectroscopy. This work highlights cationic microenvironment engineering as a concise and general strategy to steer multi‐step CO 2 electroreduction toward deep reduction products.