A One-Pot Route to Fine-Tuned Hypercrosslinked Polymer Solid Acid Catalysts

Highly acidic sulfonated polymers are promising heterogeneous catalysts due to their excellent chemical and thermal stability, as well as the possibility of employing low-cost synthesis routes. However, their production is time consuming and control of their chemical and physical properties is often difficult. Here, we produce sulfonated hypercrosslinked polymers using chlorosulfonic acid as a dual polymerisation catalyst and sulfonation agent, consolidating a conventional two-step process into a one-pot reaction. The synthesis time of the networks is reduced from 5-6 days to <24 hours, while significantly lowering or eliminating the requirement of some reagents. Furthermore, these sulfonated networks display superior acid site densities and porous properties to conventional equivalents. By varying the ratio of aromatic monomer with the multifunctional chlorosulfonic acid at the synthetic stage, excellent control over the polymers’ porous properties and sulfonation density is achieved, permitting judicious catalyst design. The ability of these polymers to act as heterogeneous acid catalysts is demonstrated via the hydrolysis of cyclohexyl acetate. Therein, it is shown that fine-tuning polymers has a dramatic effect on their catalytic performance and allows for the identification of key catalyst properties for optimal conversion.