ω-Sulfonic-perfluoroalkylated poly(styrene–maleic anhydride)/silica hybridized nanocomposite as a new kind of solid acid catalyst

A new kind of ω-sulfonic-perfluoroalkylated poly(styrene–maleic anhydride)/silica hybrid nanocomposite FSMA/SiO2 has been synthesized under mild conditions by perfluoroalkylation of styrene–maleic anhydride copolymer (SMA) with ω-fluorosulfonylperfluorodiacyl peroxides (SFAP), and followed in turn by aminolysis using (3-aminopropyl)triethoxysilane (APTES), alkali hydrolysis, gelation with tetraethoxysilane (TEOS) and finally acidification. The hybrid solid acid FSMA/SiO2 with terminal perfluoroalkylsulfonic and carboxyl groups was characterized by FTIR, SEM, TEM, TGA, XPS, EDX, acidimetry and nitrogen sorption technique. Its pore structure, acid strength and acid amount were easily modulated by controlling the gelation and perfluoroalkylation conditions. The catalytic activity and selectivity, as well as reusability of FSMA/SiO2 were tested in three important reactions, namely, cyclization of pseudoionone, condensation of indole and esterification of benzoic acid. Owing to the higher exchange capacity than that of Nafion/SiO2, and the stronger acidity than that of Amberlyst-15, the nanocomposite FSMA/SiO2 showed higher activity and selectivity than these commercial solid acids in the reactions.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (184 K)Download as PowerPoint slideHighlights► The nanocomposite (FSMA/SiO2) bearing mixed acids was synthesized in mild condition. ► FSMA resin was uniformly distributed in silica framework through covalent linkage. ► The acidic amount and pore structure of FSMA/SiO2 are adjusted simultaneously. ► The acidity of FSMA/SiO2 is easily regulated for various catalytic processes. ► FSMA/SiO2 has showed high activity in cyclization, condensation and esterification.