A Thiophene-based and Sulfur-enriched Highly Conjugated Hyper-Crosslinked Polymer for Efficient Sequestration of Iodine from Various Media

Abstract

A thiophene-based hyper-crosslinked polymer (Bi-Thio HCP) was synthesized using commercially available 2,2'-bithiophene as a monomer via Friedel-Crafts alkylation reaction. The obtained Bi-Thio HCP exhibits a high surface area, hierarchical porosity, and an abundance of electron-rich binding sites, facilitating efficient and rapid iodine uptake. The Bi-Thio HCP demonstrated outstanding iodine capture capabilities, with an adsorption capacity of 1.96 g/g in the vapor phase at 350 K and a maximum uptake capacity of 1.66 g/g for triiodide (I₃⁻) in aqueous phase at 298 K. The distribution coefficient (Kd) values greater than 10⁴ mL g⁻¹ associated with I3− capture, indicate the affinity of an adsorbent material towards the adsorbate. The trapped iodine can be readily released by simple heating at an elevated temperature or by soaking in an alcoholic solvent (such as methanol and ethanol) at room temperature. The Bi-Thio HCP can be recycled for at least five cycles without any significant decrease in removal efficiency, enabling its use in sustainable applications. In this study, the adsorption capacities and mechanisms of iodine adsorption by Bi-Thio HCP material were examined using Density Functional Theory (DFT) computations. Overall, the Bi-Thio HCP is a highly competitive option as an adsorbent for iodine sequestration due to its ease of synthesis using readily available monomers and scalable reaction conditions.