Precise Design of Sulfonated Polymer Aerogels with Tunable Hierarchical Pores: Unraveling the Structure–Adsorption Relationship for Micropollutant Removal

The balance among adsorption capacity, adsorption rate, and adsorption selectivity usually poses a fundamental challenge in the design of porous adsorbents. This intrinsic conflict stems from an unavoidable trade-off: the improvement of adsorption selectivity generally requires the grafting of abundant adsorption sites, which inevitably causes pore narrowing or even blockage and further impairs both adsorption capacity and adsorption rate. Traditional solutions include modifying morphological structures and constructing hierarchical pore architectures for functional porous adsorbents. However, the relationship between hierarchical pore architectures and adsorption activity remains highly unclear and insufficiently understood, which prevents the rational design and synthesis of high-performance porous adsorbents. Herein, a series of sulfonated porous aerogels were designed and fabricated to unravel the porous structure–adsorption activity relationship for micropollutant removal. The resulting aerogels feature systematically regulated macroporous structures while maintaining nearly identical microporous structures and sulfonic acid contents. Adsorption experiments reveal that when the microporous structures and sulfonic acid contents remain basically consistent, the adsorption rate increases with an increasing macropore size of the sulfonated porous aerogels. This clear trend confirms that the adsorption rate of micropollutants is positively correlated with the macropore size but independent of the microporous structures. The largest macropore size endows PAF-524-SO3H aerogels with the fastest adsorption rate toward methylene blue, rhodamine B, ciprofloxacin, and tetracycline at an initial concentration of 200 ppm. Meanwhile, the micropollutant adsorption capacity remains nearly constant with an increase in macropore size, suggesting that microporous structures directly dictate the adsorption capacity rather than the adsorption rate. Moreover, PAF-524-SO3H exhibits strong anti-interference capability and maintains excellent adsorption efficiency under various complex aqueous conditions, including variable pH and temperature, tap water, and coexisting competing ions. This work not only constructs sulfonated porous aerogels with an ultrahigh removal rate for cationic pollutants and antibiotics but also clearly demonstrates the relationship between adsorption activity and pore structure.