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A Pyridyltriazol Functionalized Zirconium Metal–Organic Framework for Selective and Highly Efficient Adsorption of Palladium

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journal contribution
posted on 20.05.2020 by Saba Daliran, Mahbobeh Ghazagh-Miri, Ali Reza Oveisi, Mostafa Khajeh, Sergio Navalón, Mercedes Âlvaro, Mansour Ghaffari-Moghaddam, Hojat Samareh Delarami, Hermenegildo García
This work reports the synthesis of pyridyltriazol-functionalized UiO-66 (UiO stands for University of Oslo), namely, UiO-66-Pyta, from UiO-66-NH2 through three postsynthetic modification (PSM) steps. The good performance of the material derives from the observation that partial formylation (∼21% of −NHCHO groups) of H2BDC-NH2 by DMF, as persistent impurity, takes place during the synthesis of the UiO-66-NH2. Thus, to enhance material performance, first, the as-synthesized UiO-66-NH2 was deformylated to give pure UiO-66-NH2. Subsequently, the pure UiO-66-NH2 was converted to UiO-66-N3 with a nearly complete conversion (∼95%). Finally, the azide–alkyne­[3+2]-cycloaddition reaction of 2-ethynylpyridine with the UiO-66-N3 gave the UiO-66-Pyta. The porous MOF was then applied for the solid-phase extraction of palladium ions from an aqueous medium. Affecting parameters on extraction efficiency of Pd­(II) ions were also investigated and optimized. Interestingly, UiO-66-Pyta exhibited selective and superior adsorption capacity for Pd­(II) with a maximum sorption capacity of 294.1 mg g–1 at acidic pH (4.5). The limit of detection (LOD) was found to be 1.9 μg L–1. The estimated intra- and interday precisions are 3.6 and 1.7%, respectively. Moreover, the adsorbent was regenerated and reused for five cycles without any significant change in the capacity and repeatability. The adsorption mechanism was described based on various techniques such as FT-IR, PXRD, SEM/EDS, ICP-AES, and XPS analyses as well as density functional theory (DFT) calculations. Notably, as a case study, the obtained UiO-66-Pyta after palladium adsorption, UiO-66-Pyta-Pd, was used as an efficient catalyst for the Suzuki–Miyaura cross-coupling reaction.