MXene-Regulated Indium-Based Metal-Organic Framework Material for Electrochemical Reduction of CO into Pure Formic Acid Aqueous Solution.

Electrochemical CO reduction reaction provides a mild avenue for resource utilization of CO. Metal-organic framework (MOF) materials are considered among the promising catalysts due to unique structural advantages. However, the catalytic performance of MOFs is hindered by poor conductivity, making it crucial to enhance the charge transfer for improved efficiency. Herein, a hybrid catalyst was constructed based on the In-based porphyrin framework (In-TCPP) and conducting MXene nanosheets for efficient CO conversion. As expected, MXene as a unique conductive support significantly improves the catalytic performance of the hybrid material, achieving a Faraday efficiency for HCOO of 94.0% with a 2.2-fold increase in the practical current density. Furthermore, a pure formic acid solution with a concentration of ca. 0.22 M was prepared via execution in a solid-state electrolyte-mediated MEA (MEA-SSE) device. Theoretical calculations and in situ ATR-FTIR spectra reveal that the introduction of MXene not only endows the hybrid material with metallic properties to facilitate charge transfer but also modulates the electronic structure to optimize the adsorption of the key intermediate *OCHO. This work enlightens the rational design of MOF-based electrocatalysts via the regulation of MXene and demonstrates the promise of the MEA-SSE device for practical CO reduction applications.