Uncovering the electrolyte-driven dynamic reconstruction of Sn-MOF toward exceptional CO2-to-formate conversion

The Sn-MOF reconstructed into a SnO nanoflower structure only upon electrolyte immersion. • The SnO nanoflower achieves >92% formate Faradaic efficiency in both H-cell and flow cell. • Its abundant grain boundaries and edge sites enhance the adsorption and stabilization of the *OCHO intermediate. • The nanoflower morphology remains stable during CO 2 reduction, contributing to sustained catalytic performance. Sn-based materials are promising for electrochemical CO 2 reduction to formate, yet the real active species and structural evolution under operating conditions remain elusive. Here, we track the spontaneous, potential-independent reconstruction of a Sn-terephthalic acid framework (Sn-PTA) in KHCO 3 electrolyte, revealing a two-stage transformation that dictates catalytic performance. Initially, the MOF decomposes into nanoflower-like SnO assemblies (Sn-PTA-180), characterized by abundant grain boundaries and edge sites that maximize active surface exposure. This metastable intermediate exhibits superior intrinsic activity, achieving a 92.7% formate Faradaic efficiency (FE) at 38.9 mA cm −2 in an H-cell and maintains 92.6% FE at 200 mA cm −2 in a flow cell. In situ ATR-SEIRAS correlates this performance to the optimized adsorption and stabilization of the *OCHO intermediate on the unique nanoflower architecture. Furthermore, we demonstrate that under cathodic bias, SnO undergoes a phase transition to metallic Sn while perfectly inheriting the advantageous morphology. This work elucidates electrolyte-driven MOF reconstruction as a powerful in situ route to engineer catalytically active interfaces, offering a new paradigm for designing high-performance pre-catalysts for efficient CO 2 -to-formate conversion. Download: Download high-res image (362KB) Download: Download full-size image