Green mechanochemical synthesis of imine-linked covalent organic frameworks for high iodine capture

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2023-08, Vol.25 (16), p.6287-6296
• Main Authors: Brown, Normanda, Alsudairy, Ziad, Behera, Ranjan, Akram, Fazli, Chen, Kuangcai, Smith-Petty, Kayla, Motley, Bria, Williams, Spirit, Huang, Wenyu, Ingram, Conrad, Li, Xinle
• Format: Article
• Language: English
• Subjects: Additives; Adsorbents; Ambient temperature; Ball milling; Charge transfer; Chemical synthesis; Environmental cleanup; Fourier transforms; Green chemistry; Iodine; Iodine 131; Iodine radioisotopes; Photoelectron spectroscopy; Photoelectrons; X ray photoelectron spectroscopy
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d3gc01927f

Covalent organic frameworks (COFs) have emerged as promising adsorbents for radioiodine capture. However, the conventional solvothermal synthesis contradicts the principles of green chemistry due to the use of hazardous solvents, long reaction times (typically 3 days), and high reaction temperatures. To address these issues, we demonstrate for the first time the green, efficient, liquid-assisted mechanochemical synthesis of COF adsorbents for high iodine capture. The ball milling synthesis was performed with various liquid additives at ambient temperature, yielding six imine-linked COFs of diverse pore sizes and functionalities in merely 1 hour. Notably, one representative COF exhibited high crystallinity and a remarkable surface area of 1387 m 2 g −1 in just 1 minute of ball milling. When tested as adsorbents for static iodine vapor capture at 75 °C, four mechanochemically synthesized COFs exhibited outstanding iodine adsorption capacities of 6.4-7.1 g g −1 , comparable to or exceeding those of solvothermally synthesized COF and most reported COF adsorbents. Furthermore, Fourier transform infrared and X-ray photoelectron spectroscopy corroborated the charge transfer between iodine and COF adsorbents. This mechanochemical methodology will pave the path for green, rapid, facile, and scalable synthesis of COFs, revealing great prospects for applications in environmental remediation and beyond. Delineated here is the first mechanochemical synthesis of covalent organic frameworks (COF) adsorbents that exhibited exceptional iodine adsorption capacities of 6.4-7.1 g g −1 , surpassing those of most existing COFs.