Electrophile-mediated ionic liquid strategy for transforming inert natural polymers into highly active iodine adsorbents

The separation and conversion of gas resources are crucial aspects of sustainable energy development. Developing general methods to overcome bottlenecks in gas adsorption and conversion within natural polymers is an urgent global concern. In this work, the use of ionic liquids as electrophiles was proposed, and the Ionic Liquid Solution Process (ILSP) was employed to prepare alginate polymers-based on natural polymers. ILSP achieved a remarkable 0-to-1 transformation in gaseous iodine adsorption, converting inactive alginic acid (∼0 g g−1 in saturated adsorption capacity) into a highly active iodine adsorbent (5.24 g g−1). It was revealed that electrophiles effectively regulated the electron cloud distribution of functional groups by replacing acidic protons on alginic acid, exerting a volumetric effect. This increased the electron density near the deprotonated carboxylic groups, enhancing the nucleophilicity of carboxylic groups. Consequently, it promoted halogen interaction between electron-rich oxygen atoms and iodine during adsorption, thereby improving the efficiency of charge transfer complex formation and polyiodide ion conversion. The ILSP strategy could provide guidance for the separation and conversion of gases such as iodine, carbon dioxide, and hydrogen.