Gamma radiation synthesized POSS crown ether polymers for efficient and selective lithium recovery from seawater

• POSS and cyclic siloxane polymers were synthesized via γ-radiation. • GMA grafting and crown ether functionalization produced lithium-selective adsorbents. • Modified POSS showed high Li⁺ capacity (∼3 mg/g), selectivity, and regeneration. • Modified POSS enabled efficient lithium recovery from real seawater. The rapid increase in worldwide demand for lithium ions (Li + ) is driven by progress in renewable energy storage systems and nuclear technology. The development of efficient recovery techniques has been required. Adsorption-based methods provided operational simplicity and environmental sustainability. However, it is limited by poor selectivity, low adsorption capacities, and complex synthesis processes. In this study, a novel and efficient strategy was developed to fabricate crown ether–functionalized polyhedral oligomeric silsesquioxane (POSS)-based polymers via gamma radiation-induced grafting followed by post-functionalization with 2-hydroxymethyl-12-crown-4 (2H12C4). The synthesized materials, P-POSS_MethylD 4 _2H12C4 and P-POSS_VinylD 4 _2H12C4, were thoroughly characterized using FT-IR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and solid-state 13 C NMR spectroscopy, confirming successful synthesis and robust structural formation. Both materials demonstrated notable Li + adsorption capacities of 2.95 and 3.05 mg/g within 5 h and exhibited high selectivity toward Li + in the presence of competing cations (Na + , K + , Mg 2+ , Ca 2+ ), with selective separation factors exceeding 4.07. They also showed excellent regeneration performance, retaining their adsorption capacity over five consecutive adsorption–desorption cycles. Moreover, the materials showed successful Li + extraction from actual seawater, highlighting their applicability in aqueous environments. This work presents a scalable, catalyst-free, and environmentally friendly platform for advanced Li + extraction materials.