Facile Synthesis of Polyarylene Ether Nitrile Adsorbent for High‐Capacity and Selective Removal of Methylene Blue

ABSTRACT In environmental remediation, high‐performance adsorbents that can selectively capture target dyes from complex water mixtures are highly desirable. However, conventional adsorbents generally suffer from low adsorption efficiency, poor selectivity, and inferior recyclability, limiting their practical wastewater treatment applications. Herein, a series of poly(arylene ether nitrile)s (PENs) bearing nitrile groups as well as tunable negatively charged sulfonate and carboxylate functionalities were synthesized via nucleophilic substitution reaction for efficient dye removal. The representative deprotonated sample, PEN(S‐P‐5/5), exhibited excellent adsorption capacity for cationic methylene blue (MB), which was significantly superior to that of the corresponding control samples. The adsorption process fitted well with the pseudo‐second‐order kinetic model and Langmuir isotherm model, with a maximum MB adsorption capacity of 746.27 mg g −1 at 298.15 K. Thermodynamic analysis further verified that the adsorption process was spontaneous and thermodynamically favorable. Impressively, PEN(S‐P‐5/5) achieved rapid and selective elimination of MB from binary dye mixtures containing methyl orange (MO), maintaining a high removal efficiency of 96% even after five adsorption–desorption cycles. Mechanistic investigations revealed that the adsorption process was dominated by chemisorption, where electrostatic interactions and π–π stacking between the PEN and MB molecules serve as the main driving force. Benefiting from its ultrahigh adsorption capacity, rapid adsorption kinetics, favorable selectivity, and excellent recyclability, the as‐prepared PEN is a promising candidate for efficient dye removal from wastewater.