Heterogenization of a Sandwich [(PW9O34)2Co4(H2O)2]10− in PCN‐222/PCN‐222(M): Exploring the Electron Transfer for Electrocatalytic CO2 Reduction

Abstract

AbstractIn this study, we designed and prepared polyoxometalate@metal‐organic framework (POM@MOF) composite catalysts through the anchoring of a sandwich POM [(PW9O34)2Co4(H2O)2]10− (shortened as P2W18Co4) to the hexagonal channel of the PCN‐222 (metal‐free) or PCN‐222(M) (M=Fe, Co) frameworks. The composite materials were applied to the electrocatalytic reduction of CO2 reaction (CO2RR) to analyse the effect of incorporating P2W18Co4 on catalytic activity. The P2W18Co4@PCN‐222 composite exhibited enhanced activity across a wide potential range (−0.60~−0.85 V vs. RHE) and an optimal FECO of 72 % at −0.75 V vs. RHE, which was more than double that of PCN‐222 (FECO=33 %). The current density surpassed that of the PCN‐222 precursors by over sixteen times at the same potential. In contrast, the P2W18Co4@PCN‐222(M) composite demonstrated decreased current density, minimal enhancement in CO2RR activity, and a competing HER behaviour. Density functional theory calculations were conducted on simplified models of P2W18Co4@H2‐TCPP and P2W18Co4@M‐TCPP to elucidate the divergent catalytic performances. The findings revealed that while both configurations exhibited the same rate‐limiting step (formation of the *COOH intermediate), a significantly reduced reaction barrier was only observed in the P2W18Co4@H2‐TCPP setup, explaining its substantial activity improvement.