In-modified Sn-MOFs with high catalytic performance in formate electrosynthesis from aqueous carbon dioxide

Electrochemical reduction of carbon dioxide (CO₂ER) has become an effective solution to relieve the energy crisis and tackle climate change. In this study, a series of tin-based organic frameworks modified by In (Sn-MOF/In) were successfully synthesized via a simple hydrothermal method and explored for high formate-selective CO₂ER. The pure Sn-MOF exhibits maximum formate selectivity with a faradaic efficiency (FE_formate) of approximately 85.0% and a current density of 15 mA cm^-2 at -1.16 V_RHE, while the In (6%)-modified Sn-MOF (Sn-MOF/In₆) delivers a much higher maximum FE_formate (around 97.5%) and a current density of 16 mA cm^-2 at -0.96 V_RHE. Remarkably, the Sn-MOF/In₆ exhibits a significantly larger specific surface area (183.3 m² g^-1) compared to the Sn-MOF (65.2 m² g^-1). These findings indicate that introducing In, an alien element with a slightly different outer orbital electron number from that of Sn, can significantly boost the selectivity and activity for CO₂ER to formate. This study presents an efficient way to modify MOF catalysts through a well-designed introducing process.