Boosting C–S Coupling for Selective Hydroxymethanesulfonate Electrosynthesis over Bimetallic Cu–Ni Sites within Covalent Organic Frameworks

Abstract Electrocatalytic C–S coupling via CO2/SO32– co-reduction represents a promising route for sustainable hydroxymethanesulfonate (HMS) synthesis, yet it still suffers from sluggish C–S coupling kinetics and severe competing side reactions. Herein, we develop bimetallic Cu–Ni sites within a covalent organic framework (CuNi-COF) catalyst for efficient and selective HMS electrosynthesis. Mechanistic investigations reveal that bimetallic Cu–Ni sites can synergistically reduce CO2 to *CHOH and promote C–S coupling of *CHOH with *SO3, while inhibiting the competing hydrogen evolution reaction, thereby resulting in a high efficiency for selective HMS synthesis. Impressively, CuNi-COF achieves the exceptional HMS yield rate of 32.8 μmol cm–2 h–1 and a Faradaic efficiency of 27.3% in a membrane electrode assembly electrolyzer, along with outstanding long-term stability for over 100 h of electrolysis. Techno-economic analysis further demonstrates the considerable economic viability of the CuNi-COF-driven electrocatalytic C–S coupling method for industrial-scale HMS production.