Preparation of Sulfonate‐Functionalized Cross‐Linked Polysulfone‐Benzoxazine/Calix[4]Arene Copolymer for Specific Adsorption of Methylene Blue

The novel cross‐linked copolymer (BPSU‐C4A‐SPS) was synthesized by the copolymerization of benzoxazine‐functionalized polysulfone (BPSU), calix[4]arene (C4A), and sodium 4‐hydroxybenzenesulfonate (SPS). The material exhibited high thermal stability with a glass transition temperature ( T g ) of 285°C and a 5% weight loss temperature ( T d5 ) of 347°C, and enhanced hydrophilicity with a water contact angle of 76.5°. Moreover, adsorption studies on MB demonstrated that BPSU‐C4A‐SPS possesses a higher adsorption capacity than the benzoxazine‐functionalized polysulfone homopolymer (BPSU‐a) and the benzoxazine‐functionalized polysulfone‐calix[4]arene copolymer (BPSU‐C4A). Adsorption followed the Freundlich isotherm and pseudo‐second‐order kinetics best describes the adsorption process of BPSU‐C4A‐SPS to MB, indicating multilayer chemisorption driven by electrostatic interactions and π‐π stacking. This work provides a scalable strategy for designing stable adsorbents with synergistic effects, suitable for industrial wastewater treatment.