Efficient capture of iodine by charge-induced effect of nitrogen-rich ionic liquids

The efficient capture of radioactive iodine in nuclear waste is vital for promoting the sustainable development of nuclear energy, protecting the environment and human health. Nitrogen-rich adsorbents have received widespread attention due to their high affinity with iodine. Herein, we present a series of nitrogen-rich heterocyclic ionic liquids based on 5-aminotetrazolate (ATILs), and fabricate four composite materials ([N1111][AT]/MF, [N2222][AT]/MF, [N3333][AT]/MF, [N4444][AT]/MF). MF with porous properties as a carrier is cost-effective and readily available. For the composite materials, the ATILs possess abundant nitrogen active sites, and the introduction of MF significantly increases their specific surface area. This greatly enhances the iodine capture performance of materials. The maximum capture capacities of [N1111][AT]/MF, [N2222][AT]/MF, [N3333][AT]/MF and [N4444][AT]/MF were 6.94 g g−1, 6.53 g g−1, 5.70 g g−1 and 4.58 g g−1, respectively. A certain correlation between capture performance and nitrogen content can be found. Increasing the nitrogen content of material can still contribute to enhancing its performance, even when the nitrogen content exceeds 35 %. FT-IR, Raman and XPS spectra confirmed that the polyiodide anions were produced via charge-inductive effect and charge transfer. The density functional theory (DFT) calculation confirmed the feasibility of nitrogen-rich strategies and the existence of strong halogen bonds between I2 and 5-aminotetrazolate anions. This work obtained a series of iodine capture materials with high nitrogen content, achieved efficient iodine capture, and demonstrated the relationship between materials with high nitrogen content and iodine adsorption performance, which will promote the design and development of novel nitrogen-rich materials for iodine capture.