Network SHCP-1 showed no measurable catalytic activity due to low acidity (S content of 0.1 mmol•g -1 ). Control experiments with non-acidic hypercrosslinked polymer equivalents confirmed that no measurable conversion was achieved without sulfonation. The more acidic SHCP-2 (S content of 0.4 mmol•g -1 ) gave substrate conversions of 31% with a high standard deviation of ± 18%, suggesting that this polymer lies at a critical concentration upon which catalytic activity depends highly on network acidity. The remaining SHCPs all achieved ≥60% conversion of cyclohexyl acetate, outperforming both the commercial resin Amberlyst-15 and homogeneous (liquid) H2SO4. Interestingly, high acid densities did not appear crucial for catalyst performance.