Nanoporous N-Rich Covalent Organic Frameworks with High Specific Surface Area for Efficient Adsorption of Iodine and Methyl Iodide

Abstract

With the rapid development of the nuclear industry, the effective treatment of radioactive iodine has become an urgent and challenging task. In this article, we synthesized a nanoporous nitrogen-rich covalent organic framework (TTA-DMTP-COF) with a specific surface area of up to 2332 m2/g for the adsorption of iodine (I2) and methyl iodide (CH3I). Adsorption experiments showed that TTA-DMTP-COF exhibited effective I2 and CH3I adsorption properties; the maximum adsorption capacity of I2 is as high as 2.59 g·g–1, and the maximum adsorption capacity of CH3I is 1.60 g·g–1. In addition, TTA-DMTP-COF can effectively adsorb iodine from an iodine–cyclohexane solution, and the adsorption amount is as high as 516.46 mg/g. Mechanistic studies have shown that I2 and CH3I enter the nanopores of COF materials and form charge transfer complexes with various functional groups in TTA-DMTP-COF (including imines, triazine moieties, and residual amino groups). The N-methylation reaction specifically binds CH3I to the nucleophilic N site and generates polyiodides during the adsorption process. Our work demonstrates that TTA-DMTP-COF is an excellent candidate material capable of capturing radioactive iodine from air and solution in harsh environments.

Linking Nitrogen-Rich Pillar[5]arene to Hyper-Cross-Linked Polymers for Efficient and Simultaneous Capture of Iodine and Methyl Iodide

“…These results were consistent with the results reported previously, , indicating that adsorption was chemically controlled and charge-transfer interactions occurred between I 2 and the active sites. In the N 1s XPS spectra of P­[5]­A-TPTA12 (Figure d), the peaks at 400.1 and 398.8 eV, assigned to sp 3 N and triazine N, shifted to 401.3 and 399.0 eV, respectively, after the adsorption of I 2 , further indicating the occurrence of charge transfer between I 2 and various N species of P­[5]­A-TPTA12 . − The PXRD patterns also supported the uptake mechanism mentioned above. Compared with that of P­[5]­A-TPTA12 (Figure S14), the PXRD pattern of I 2 -saturated P­[5]­A-TPTA12 contained weaker diffraction peaks, indicating that I 2 -saturated P­[5]­A-TPTA12 was still amorphous.…”

“…Because radioactive I 2 and CH 3 I coexist in the exhaust stream, it is urgent to remove them concurrently. However, iodine and methyl iodide are usually adsorbed separately, and only five types of adsorbents, namely, three imine-linked covalent–organic frameworks (COFs), − one nitrogen-rich silk fibroin aerogel, and one highly hydrophobic zeolite, have been investigated for the simultaneous capture of I 2 and CH 3 I. Although these COFs exhibit high adsorption ability for both iodine and methyl iodide, they are unstable in acidic, humid, and warm environments.…”

Light-Gating Crystalline Porous Covalent Organic Frameworks

“…We further investigated kinetics to reveal the uptake rate constant. The I 2 adsorption by [E-4F-Azo] 0.17 -TPB-DMTP-COF follows a pseudo-second-order kinetics, 36,37 which gives rise to an average adsorption rate of 2.70 × 10 −2 g g −1 h −1 , which is evaluated at the point of 80% full capacity 38,39 (Figure 3F, red curve and Table S5). As the X value was increased to 0.34, [E-4F-Azo] 0.34 -TPB-DMTP-COF exhibited an average adsorption rate of 2.55 × 10 −2 g g −1 h −1 (Figure 3F, blue curve and Table S5), while retaining a pseudo-second-order kinetics.…”

Synthesis of Triazole-Linked Porous Cage Polymers: Modulating Cage Size for Tailored Iodine Adsorption

“…The research on iodine capture centers on developing high-performance adsorbent materials. − Various adsorbents, such as silver-based zeolites, activated carbons, metal–organic frameworks (MOFs), ,− covalent organic frameworks (COFs), − and porous organic polymers (POPs), − have been extensively studied for their potential use in iodine removal. In addition to these porous materials, porous organic cages (POCs) have recently been utilized as alternative adsorbents to capture iodine. ,− Compared to the extended polymeric materials, like MOFs, COFs, or POPs, that only have external pores, POCs comprise discrete organic cage molecules with intrinsic cavities and accessible windows.…”