Novel cotton fiber-covalent organic framework hybrid monolith for reversible capture of iodine

The cellulose-based materials are new types of advanced materials combining pristine cellulose with functional materials for specific applications. In this study, a novel cotton fiber (CF)–covalent organic framework (COF) hybrid monolith was prepared for the efficient capture of iodine in vapor and solution. The cotton fibers were first modified with (3-aminopropyl)trimethoxysilane via silylation reaction to generate amino functions on the surface of the fibers, and then the COFs grafted subsequently. The obtained CF/COF hybrid monolith has been characterized by infrared spectra, powder X-ray diffraction, elemental analysis, scanning electron microscope, thermo-gravimetric analysis, and nitrogen adsorption–desorption analysis, and then it was used as adsorbent for removing iodine. The grafting of COFs on the cotton fiber matrix was calculated to be about 12.28 wt%, which increased the BET specific surface area of the cotton fiber from 1.9 to 166 m²/g. The CF/COF monolith displayed excellent capture ability for iodine vapor with adsorption capacity up to 823.9 mg/g, and it also showed remarkable adsorption ability for iodine in cyclohexane solution. The hybrid monolith can be easily regenerated by washing with methanol, and it showed good reusability. Moreover, the CF/COF monolith presented good thermal stability with a decomposition temperature above 300 °C. This strategy for combining COFs with cotton fibers will pave the way for the development of novel efficient adsorption materials for radioiodine during nuclear waste disposal.