Stabilizing Highly Active Metastable Bi (101) Facet via Covalent Organic Frameworks to Break Activity-Stability Trade-off in CO-to-HCOOH Electrocatalysis.

Electrochemical CO reduction reaction (eCORR) offers a sustainable route to convert greenhouse gases into value-added chemicals. Bismuth (Bi) has emerged as a promising electrocatalyst for CO-to-HCOOH conversion due to its low cost, nontoxicity, and favorable adsorption properties for the key *OCHO intermediate. However, its relatively contracted 5d and expanded 6p orbitals lead to inevitable thermodynamically driven structural reconstruction during eCORR, resulting in a persistent trade-off between activity and stability. Here, by tuning the balance between the electrochemical and thermodynamic steady states of layered Bi species leveraging interlayer interactions and spatial confinement provided by a two-dimensional covalent organic framework (COF), we achieve the selective exposure and stable maintenance of the highly active, metastable Bi (101) facet during eCORR for the first time. The resulting catalyst achieves top-tier performance with 98.7 ± 0.1% HCOOH selectivity, exceptional stability over 230 h, and a flow cell HCOOH partial current density exceeding 350 mA cm at -1.0 V versus RHE, ranking it among the most efficient and stable electrocatalysts reported to date.