Designing atomically precise and robust covalent organic frameworks for enhanced iodine/iodate uptake: structures with and without phenol hydroxy groups

Abstract

Iodine/iodide/iodate represents a highly recalcitrant environmental pollutant, whose bioaccumulation poses significant threats to human health. Despite the development of various removal methods, the targeted design of adsorbents with high efficiency and reusability for iodine/iodide/iodate extraction remains largely unexplored. Herein, we present the rational design and synthesis of triphenylamine (TPA)-based Schiff covalent organic frameworks (COFs) with tailored phenol hydroxyl sites (COF-BT, COF-TP, and COF-Dha) for iodine/iodide/iodate removal. The incorporation of nitrogen sites and phenol hydroxyl groups endows the COFs with exceptional stability and outstanding iodine uptake capacity. Notably, COF-Dha demonstrates remarkable performance across diverse iodine forms: achieving a maximum adsorption capacity of 4.9 g g⁻¹ for iodine vapor, 2.29 g g⁻¹ for polyiodide solutions, 1.26 g g⁻¹ for iodine–cyclohexane solutions, and 2.5 g g⁻¹ for CH₃I vapor. Moreover, the presence of para-hydroxyl groups in COF-Dha enables excellent redox activity toward iodate, facilitating the reduction of IO₃⁻ and exhibiting an adsorption capacity of 467 mg g⁻¹. The structural diversity of these TPA-COFs leads to superior physicochemical adsorption performance for iodine/iodide/iodate removal, providing a reference for the rational development of novel COF-based materials for environmental iodine/iodate remediation.