Covalent organic frameworks functionalized with thioether or vinyl groups for efficient and rapid capture of multiple iodine pollutants

Abstract

Efficient sequestration of radioactive iodine species (I₂, CH₃I, I₃⁻) is vital for nuclear safety and environmental protection. However, developing multifunctional adsorbents that remain effective under diverse conditions remains a significant challenge. Herein, we report two functionalized PD-COFs (PD-WS and PD-WY) with moderate crystallinity, outstanding thermal stability, and robust chemical resistance. They exhibit superior adsorption performance in both gas and liquid phases. Specifically, at 75°C, PD-WY achieves capacities of 4.88 g g⁻¹ for I₂, 1.55 g g⁻¹ for CH₃I, and 5.55 g g⁻¹ for the I₂/CH₃I mixture, while high capacities are also retained at room temperature. In solution, PD-WY adsorbs up to 3.56 g g⁻¹ of I₃⁻ in water and 2.00 g g⁻¹ of iodine in cyclohexane. These COFs display rapid kinetics (K_80% = 3.25 g g⁻¹ h⁻¹ for I₂ and 7.89 g g⁻¹ h⁻¹ for I₃⁻) and excellent selectivity. Mechanistic studies indicated that the excellent iodine affinity of PD-COFs arises from their rich electronic structures, abundant active sites, and charge transfer interactions. These findings position PD-COFs as highly promising adsorbents for nuclear waste treatment and environmental remediation.