Post-Synthetically Modified Metal Organic Framework\nFunctionalized with a 1,2-Dihydroxybenzene Chelating Unit for Efficient\nRemoval of Thorium and Uranyl Ions from Radioactive Waste

Metal organic frameworks (MOF) are\nproven to be the efficient solid\nphase sorbents for uranium and thorium, the driver fuels for the present\nand future nuclear power program of India. In this article, a novel\nsorbent material (MOF-DHB) has been dove-tailed by a post-synthetic\nmodification technique (here, 1,2-dihydroxybenzene functionalized\non the surface of UiO66-NH<sub>2</sub>), and sorption efficacy of\nthe material for UO<sub>2</sub><sup>2+</sup> and Th<sup>4+</sup> from\nacidic solutions has been explored for the first time. It exhibits\nvery high (>98%) removal efficiency for both actinides compared\nto\nthe unfunctionalized MOF (with 52% and 65% for UO<sub>2</sub><sup>2+</sup> and Th<sup>4+</sup>, respectively). The surface functionalization\ninduced the enhancement in the saturation sorption capacity values\nof UO<sub>2</sub><sup>2+</sup> and Th<sup>4+</sup> (nearly 1.3-fold\ncompared to parent MOF). Reusability has been demonstrated by quantitative\nback extraction of metal ions using suitable stripping agents and\nsubsequent use of the sorbent for new extraction without any performance\ncompromise. The synthesized MOF is stable up to 500 kGy dose and can\nbe applied for more than five cycles of operation. FTIR analysis illustrates\nthat major modes of coordination in MOFDHB and MOF are through phenolic\n−OH and −NH<sub>2</sub> groups.