Radiation Synthesis and Adsorption Properties of Imidazolium-Based Bromide Ionic Liquid Grafted Covalent Organic Framework

Abstract

In the fields of spent fuel reprocessing and nuclear environmental remediation, it is important to design and synthesize adsorbent materials with high efficiency and selectivity for separating TcO4- and its analog ReO4-. The porous and crystalline covalent organic framework (COF) materials show unique advantages in radionuclide separation. In this work, a vinyl-rich two-dimensional COF material (TbDa-COF) was synthesized firstly. The ionic liquid 1-vinyl-3-ethyl imidazolium bromide (C2vimBr) as a monomer was successfully grafted onto TbDa-COF by using γ-ray pre-irradiation induced grafting polymerization. The crystallinity and porosity of the TbDa-COF remains after grafting with ionic liquid. The effect of concentration of ionic liquid monomer on the grafting is the most important. The grafting yield increases with the rising of monomer content, and solvent has slight effect on the grafting yield of products. The prepared ［C2vimBr］-TbDa-COF material shows excellent adsorption performance for ReO4-. The adsorption equilibrium can be reached within 2 min, and the maximum adsorption capacity is up to 420 mg/g. The introduction of long hydrophobic alkyl groups on the graft chain in ［C2vimBr］-TbDa-COF is conducive to improving the adsorption selectivity towards ReO4-. This work demonstrates the great potential of ionic liquid modified COF for spent fuel reprocessing and nuclear environmental remediation.