Molecular Iodine Capture by Covalent Organic Frameworks

Abstract

The effective capture and storage of volatile molecular iodine from nuclear waste is of great significance. Covalent organic frameworks (COFs) are a class of extended crystalline porous polymers that possess unique architectures with high surface areas, long-range order, and permanent porosity. Substantial efforts have been devoted to the design and synthesis of COF materials for the capture of radioactive iodine. In this review, we first introduce research techniques for determining the mechanism of iodine capture by COF materials. Then, the influencing factors of iodine capture performance are classified, and the design principles and strategies for constructing COFs with potential for iodine capture are summarized on this basis. Finally, our personal insights on remaining challenges and future trends are outlined, in order to bring more inspiration to this hot topic of research.

Covalent Organic Framework as a Metal-Free Photocatalyst for Dye Degradation and Radioactive Iodine Adsorption

“…Peaks at 618.67 and 630.15 eV are attributed to the presence of 3d 5/2 and 3d 3/2 of molecular iodine, while the simultaneous appearance of peaks at 620.58 and 632.05 eV is due to the presence of polyiodide (I 3 − and I 5 − ) anions. 6,63,64 Moreover, for iodine-adsorbed COF, the N 1s spectrum (Figure S13b, Supporting Information) shows peaks at 398.4, 399.8, and 400.2 eV for triazine, triphenylamine, and imine nitrogen, respectively. Interestingly, such a nitrogen environment encounters little high binding energies compared to the pristine COF (see Figure 3a).…”

A Porous π-Stacked Self-Assembly of Cup-Shaped Palladium Complex for Iodine Capture

“…To give insights into the I 2 adsorption mechanism, we conducted Fourier transform infrared (FT-IR) spectroscopy ( Figure 4 a) and X-ray photoelectron spectroscopy (XPS) ( Figure 4 b–d) studies on compound 1 before and after I 2 uptake. After I 2 loading, the characteristic band at ∼1634 cm −1 assigned to the C=N stretching vibration decreases significantly [ 14 , 19 , 29 , 33 , 34 ]. A pair of I 3d signals can be seen from the XPS of the sample after I 2 uptake ( Figure 4 a,b).…”

“…As for 131 I, it is often combined with hydrocarbons, giving rise to harmful organic compounds such as methane iodide [ 9 , 10 , 11 , 12 ]. Among various possible radioactive iodine species, molecular iodine (I 2 ) is the main pollutant in nuclear waste disposal and the nuclear accident [ 13 , 14 ]. Therefore, acquiring adsorbents for effective capture of I 2 is on demand.…”

“…In spite of that significant progress on adsorbents for I 2 capture has been achieved, there is still much room to improve the performance of adsorbents for I 2 capture. In general, a high-performance I 2 capture material needs to simultaneously meet the following requirements: high I 2 adsorption capacity and kinetics under industrial conditions, high selectivity, a long retention time of the adsorbed I 2 , and great recyclability and low-cost [ 14 ]. The search for high-performance I 2 capture adsorbents is still ongoing.…”

Two New 1D Supramolecular Compounds Based on PbI2 for Efficient Iodine Capture

“…Supramolecular materials combine the stability of inorganic materials and the adjustability of organic materials, which gives organic–inorganic hybrid materials unique advantages in the field of iodine molecular enrichment [ 12 ]. Some electron-rich groups, such as −NH, −NH 2 , −C=N−, heterocyclic (S, P), aromatic ring, and so on, can adsorb electron-deficient I 2 by forming charge transfer complexes, so as to improve the adsorption capacity and adsorption rate by adjusting the adsorption dynamics between organic–inorganic hybrid materials modified with electron-rich functional groups and iodine [ 28 ]. Our research group has been engaged in the preparation and performance research of supramolecular compounds for a long time [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ].…”