Ionic Functionalization of Multivariate Covalent Organic Frameworks to Achieve an Exceptionally High Iodine‐Capture Capacity

Abstract

Adsorption‐based iodine (I2) capture has great potential for the treatment of radioactive nuclear waste. In this study, we apply a “multivariate” synthetic strategy to construct ionic covalent organic frameworks (iCOFs) with a large surface area, high pore volume, and abundant binding sites for I2 capture. The optimized material iCOF‐AB‐50 exhibits a static I2 uptake capacity of 10.21 g g−1 at 75 °C and a dynamic uptake capacity of 2.79 g g−1 at ≈400 ppm I2 and 25 °C, far exceeding the performances of previously reported adsorbents under similar conditions. iCOF‐AB‐50 also exhibits fast adsorption kinetics, good moisture tolerance, and full reusability. The promoting effect of ionic groups on I2 adsorption has been elucidated by experimentally identifying the iodine species adsorbed at different sites and calculating their binding energies. This work demonstrates the essential role of balancing the textural properties and binding sites of the adsorbent in achieving a high I2 capture performance.

Electrocleavage Synthesis of Solution-Processed, Imine-Linked, and Crystalline Covalent Organic Framework Thin Films

“…25 COF powders and aerogels have been studied for the capture and storage of radiological iodine and have achieved a high iodine uptake of over 10 g g −1 . 26 dozens of hours to reach an adsorption equilibrium. Such slow kinetics results from the slow diffusion of iodine in the long one-dimensional (1D) channels in the COF powders and aerogels; the slow adsorption kinetics lead to a substantial issue for practical utilization.…”

Water-stable porous Al24 Archimedean solids for removal of trace iodine

“…As can be seen from the expanded XPS spectra (Fig. 6a ), the two peaks for the I3 d transition move to the higher binding energy with increased iodine loading, indicating an enhanced degree of aggregation 47 , 48 . The intensities of the Raman signals also increase with the concentration of the I 2 /KI solution used (Fig.…”

Combination of aluminum molecular rings with chemical reduction centers for iodine capture and aggregation

“…S43 and S44 †). 10,55 The absorption peak of I 2 may be blue-shifted to 170 cm −1 due to host-guest interactions. 12 In the XPS spectra, the binding energy at 630 eV and 618 eV is associated with the I 3 − I 3d 5/2 and I 3d 3/2 peaks, which are present in both I 2 @AlOC-151 and I 2 @AlOC-155 (Fig.…”

“…1 Therefore, there is an urgent need to develop new materials and technologies that capture, immobilize and store iodine. Compared to the common materials 2 (carbon, 3 silverbased materials, 4 silicon 5 aerogel materials, 6 nanoporous materials 7,8 and COFs 9,10 ), the visualization of crystalline materials by single-crystal X-ray diffraction (SCXRD) provides an effective method to understand the interactions between hosts and guests. Among them, crystalline metal-organic frameworks serve as an exciting avenue to capture iodine due to their facile functionalization, stable and high surface area, porous nature, and the controllability of framework components.…”