A nitrogen-rich conjugated covalent organic framework enabling effective iodine adsorption

Abstract

Radioactive iodine is a hazardous product generated by nuclear energy, and it is important to design new porous materials to capture and store iodine. In this work, a nitrogen-rich conjugated covalent organic framework (JLNU-318) was constructed. JLNU-318 has high crystallinity, large specific surface area (1008.88 mg²/g), and strong thermal and chemical stability, which makes it an ideal choice for iodine adsorption. JLNU-318 exhibits iodine adsorption capacity of 4.25 g g⁻¹ at 75 °C for 50 h, and recycles five times without significantly decrease in its adsorption capacity. Theoretical calculations demonstrated that the strong interactions between the nitrogen-rich (imine N, sp³ N) and conjugated structures (C═C) in JLNU-318 and the iodine molecules resulted in the transformation of iodine vapor into polyiodide anions, which were firmly adsorbed in the pores. This work establishes a novel approach to enhance the performance of COFs in the field of iodine adsorption.