Plasma-driven sulfonation activation: Unveil a green pathway for sulfonated carbon acid catalysts

Sulfonated carbon catalysts are widely employed in acid-catalyzed biomass transformations. However, their conventional synthesis typically relies on harsh conditions. Plasma-driven sulfonation has recently emerged as a sustainable alternative that enables effective functionalization using dilute sulfuric acid with short treatment times, but the underlying reaction mechanisms remain poorly understood. Herein, we elucidate the liquid-phase reaction pathways governing plasma-assisted carbon sulfonation by combining DC plasma treatment with controlled UV and heat activation of sodium persulfate (Na 2 S 2 O 8 ) solutions as reference systems. Comparative analysis reveals that sulfate radicals (∙SO 4 – ), generated via plasma–liquid interactions or persulfate activation, play a key role in sulfur incorporation, leading to the formation of sulfonic (–SO 3 H) and sulfate ester (–OSO 3 H) groups alongside oxygen-containing functionalities on carbon surfaces. This work establishes a mechanistic framework for plasma-driven carbon sulfonation and provides fundamental insights into plasma–liquid chemistry, supporting the rational design of sustainable sulfonated carbon catalysts under mild conditions.