Author: Linwei He, Long Chen, Xinglong Dong, Shitong Zhang

Corresponding author: Wang Shu concave, Yu Han

Correspondence: Soochow University, King Abdullah University of Science and Technology

Research highlights:

1. A new design concept of iodine-absorbing material is proposed.

2. Nitrogen-rich COF (SCU-COF-2) exhibits super-high iodine absorption and CH3I absorption.

3. Water has little effect on the iodine intake of SCU-COF-2.

Research Background

The capture of radioactive iodine species during nuclear fuel reprocessing and nuclear accidents is critical to nuclear safety, environmental protection and public health. Under actual dynamic conditions, the previously reported emerging materials for iodine absorption cannot be compared with commercial zeolite and activated carbon.

Introduction

Recently, Professor Wang Panwa of Soochow University and King Abdullah University of Science and Technology Yu Han designed and synthesized a robust nitrogen-rich COF (SCU-COF-2), which aims to selectively remove and remove elemental iodine (I2) and Methyl iodide (CH3I).

Point 1: Preparation of nitrogen-rich covalent organic framework

In order to enhance the host-guest interaction between the COF framework and iodine, the researchers chose 2,20-bipyridine-5,50-dialdehyde (2,20-BPy-DCA) as the functional ligand. At the same time, the nitrogen atom in pyridine can react with organic iodine through methylation reaction to form a COF material with organic iodine capturing ability.

Point 2: SCU-COF-2 structure characterization

Studies have found that the highly functionalized bipyridine building block is expected to interact with I2 molecules through the electron pair effect that enhances binding affinity and act as a substrate for methylation reactions to immobilize CH3I. In addition, the fully conjugated and highly hydrophobic framework structure of SCU-COF-2 gives it good radiation, humidity and thermal stability, which is essential for extreme operating conditions in UNF post-processing.

Point 3: Iodine Absorption Test

Through penetration experiments under high humidity and high temperature, it has proved its good iodine trapping ability. The experimental results show that the ultra-high iodine absorption under static adsorption conditions reached 6.0 g g-1, and the absorption of CH3I reached 1.45 g g-1. In addition, the penetration experiment under high humidity and high temperature achieved dynamic conditions Record high iodine adsorption capacity.

Point 4: Theoretical calculation

The researchers used density functional theory (DFT) calculations to reveal the capture site and adsorption mechanism. The introduction of N into the benzene ring (creating a pyridine ring) provides a large number of adsorption sites not only in the hexagonal cavity but also in the triangular cavity. In addition, the dissociative adsorption (chemisorption) of methyl iodide is thermodynamically favorable at the pyridine nitrogen site.

references

He et al., A nitrogen-rich covalent organic framework for simultaneous dynamic capture of iodine and methyliodide, Chem (2020)

DOI: 10.1016/j.chempr.2020.11.024

https://doi.org/10.1016/j.chempr.2020.11.024

Source of information: Wonders

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