Three HO₃S-functionalized porous organic polymers (HO₃S-POPs) with high surface areas (500–700 m²/g) and a broad range of porosity profiles were synthesized and tested against homogeneous-acid analogs and commercially available acid resins to evaluate their relative catalytic activities in the acid-catalyzed conversion of fructose to HMF. Comparison of fructose conversions and HMF yields demonstrates that the sulfonated POPs with hierarchical porosity can achieve catalytic activities that rival those of their homogeneous counterparts. The associated HMF selectivities represent optimized values that increase with higher temperature and faster heating, both of which can reduce the reaction time and limit product decomposition. Due to their intrinsically high mesoporosity and number of accessible acid sites, these HO₃S-POPs also outperform the commercially available Amberlyst 15 resin catalyst and its crushed variant.