Highly Efficient and Recyclable Sulfonic Acid-Modified Polypropylene Fiber Catalysts for Epoxide Ring-Opening, Aldol Condensation and Heterocyclic Synthesis

Abstract

Polypropylene fibers (PPFs) have gained significant attention as promising catalyst supports because of their excellent physical and chemical properties. Herein, we report the synthesis of a polypropylene fiber catalyst (PPCSAF) functionalized with sulfonic acid via a low-temperature solution grafting approach. As a multifunctional catalyst, PPCSAF facilitated reactions involving three distinct types of chemical bonds with remarkable efficiency. In the formation of C–O bonds, PPCSAF achieved a 98.2% yield and 96.9% regioselectivity in the ring-opening reaction of epichlorohydrin at 25 °C within 24 hours, significantly outperforming the conventional H2SO4 catalytic system. Mechanistic studies revealed that the reaction follows a “capture–nucleophilic addition–release” pathway, in which the functionalized fiber effectively concentrates the substrate and promotes its conversion to the desired product, ensuring high efficiency and selectivity. Furthermore, PPCSAF demonstrated excellent catalytic activity in C–C bond formation, achieving remarkable yields of 91%-98% in the aldol condensation of cyclohexanone with aromatic aldehydes, showing broad substrate applicability. Additionally, it exhibited high activity in the formation of C–N bonds during the synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives, yielding 91–99% with a wide range of substrates. These findings underscore the versatility, efficiency, and broad applicability of PPCSAF. The catalyst also demonstrated excellent recyclability, maintaining high performance over five cycles, and was scalable for gram-scale reactions. Overall, PPCSAF combines high efficiency, selectivity, recyclability, and scalability, making it as a promising catalyst for industrial applications and sustainable catalytic processes.