In situ functionalized sulfonic copolymer toward recyclable heterogeneous catalyst for efficient Beckmann rearrangement of cyclohexanone oxime

•In situ sulfonated polymer is applied in Beckmann rearrangement for the first time.•The catalyst possesses plenty of mesopores and high sulfur content.•High yield is achieved within short reaction time of 1 h.•The catalyst shows well recyclability and substrate compatibility.

Exploring environmentally friendly, efficient and recyclable heterogeneous catalysts for low-temperature liquid-phase organic reactions are important for the development of green and sustainable processes. In this work, we applied an in situ sulfonated polymeric solid acid H-PDVB-SO3H for catalyzing liquid-phase Beckmann rearrangements for the first time, with post-sulfonated sample and other various counterparts as control catalysts. H-PDVB-SO3H was prepared by copolymerization of divinylbenzene with sodium p-styrene sulfonate under solvothermal condition, followed by ion-exchanging to convert the polymer into proton form. It possessed a large surface area, plenty of mesopores and high sulfur content, and exhibited the high yield to ε-caprolactam (75%) with quite steady reusability in the heterogeneous Beckmann rearrangement of cyclohexanone oxime. The catalyst also showed good substrate compatibility with such a high reaction rate that the reaction time was as short as 1 h. No any co-catalysts or metals were used in the catalytic system, making the catalyst an environmentally friendly and efficient candidate for Beckmann rearrangements.

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