Nanocasting Design and Spatially Selective Sulfonation of Polystyrene-Based Polymer Networks as Solid Acid Catalysts

Nanocasting is a general and widely applied method in the generation of porous materials during which a sacrificial solid template is used as a mold on the nanoscale. Ideally, the resulting structure is the inverse of the template. However, replication is not always as direct as anticipated, so the influences of the degree of pore filling and of potential restructuring processes after removal of the template need to be considered. These apparent limitations give rise to opportunities in the synthesis of poly(styrene‐co‐divinylbenzene) (PSD) polymer networks of widely varying porosities (BET surface area=63–562 m2 g−1; Vtot=0.18–1.05 cm3 g−1) by applying a single synthesis methodology. In addition, spatially selective sulfonation on the nanoscale seems possible. Together, nanocasting and sulfonation enable rational catalyst design. The highly porous nanocast and predominantly surface‐sulfonated PSD networks approach the activity of the corresponding molecular catalyst, para‐toluenesulfonic acid, and exceed those of commercial ion‐exchange polymers in the depolymerization of macromolecular inulin. Casting director: The nanocasting of polystyrene‐based polymer networks is investigated, highlighting significant restructuring processes that can occur during removal of the template, post‐synthesis heat treatment, or solvent immersion. Analysis of the nanocast polymers sulfonated in the liquid phases suggests that spatially selective sulfonation of the polymer is possible, allowing a rational catalyst design for the conversion of inulin.