Self-assembly synthesis of a high-content sulfonic acid group functionalized ordered mesoporous polymer-based solid as a stable and highly active acid catalyst

Abstract

A stable and highly active ordered mesoporous polymer-based acid catalyst has been prepared via a simple surfactant templating approach and oxidation treatment. The composition and nanostructure are characterized by XRD, NMR, XPS, TEM, nitrogen sorption, elemental and chemical analysis. The sulfonic acid groups have been anchored within the well-arranged channels of the polymer-based matrix. Even with a high –SO₃H group loading (up to about 27.4 wt%) on the mesoporous polymer-based material, the ordered mesostructure and high surface area (∼400 m² g⁻¹) can be retained and the functional moieties are highly chemically accessible. With the large number of acid sites (0.93–2.38 H⁺ mmol g⁻¹ determined by acid–base titration) and the hydrophobic character, the mesoporous polymer-based solid exhibits unique catalytic performance in acid-catalyzed reactions such as condensation and acetalization, not only high activity (per site yield of bisphenol-A is over 45 in the condensation of phenol and acetone) but also excellent stability. Loss in acidic loading and activity is negligible even after the catalyst is reused 20 times in the acetalization of butanediol and aldehyde. The stability is most likely attributed to the hydrophobic nature of the mesoporous polymer-based solids, which favors the diffusion of water and thereby inhibits the poisoning of acidic sites caused by water generating in the reaction. Moreover, with large mesopores, the diffusion of reactants and products can be promoted and hence the catalytic activity can be further increased.