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The influence of water in the synthesis of Zr-based metal-organic framework UiO-66: isolation and reactivity of the new species [ZrCl(OH)2(DMF)2]Cl

preprint
revised on 03.04.2020 and posted on 06.04.2020 by Marco Taddei, Jeroen A. van Bokhoven, Marco Ranocchiari
We recently discovered that aging a solution of zirconium(IV) tetrachloride (ZrCl4) in N,N-dimethylformamide (DMF) in the presence of water, followed by addition of terephthalic acid linker, reduces the crystallite size of the metal-organic framework UiO-66 [Chem. Commun. 2016, 52, 6411-6414]. In an effort to shed light into the nature of the aging effect and on its relationship with the crystallite size of UiO-66, we report here the isolation and structural characterization of a microcrystalline zirconium-based compound of formula [ZrCl(OH)2(DMF)2]Cl, which is formed during the aging process. The Zr(IV) ions are coordinated by hydroxide, DMF and chloride to produce a one-dimensional polymer. Thanks to the presence of two –OH groups per zirconium atom, [ZrCl(OH)2(DMF)2]Cl is a suitable precursor for the synthesis of UiO-66 in dry DMF, affording a product having smaller crystallite size than that obtained from a reaction mixture having the same chemical composition, but using ZrCl4 as the Zr(IV) source. By starting from ZrCl4 and generating [ZrCl(OH)2(DMF)2]Cl in situ in solution through aging, we obtained smaller crystallites as the aging time increased, proving that [ZrCl(OH)2(DMF)2]Cl plays a role in the aging process. The possible role of [ZrCl(OH)2(DMF)2]Cl in the crystallization mechanism of UiO-66 is also discussed, with emphasis on its relationship with the amount of water in the reaction mixture.

Funding

Energy System Integration platform at Paul Scherrer Institute

History

Email Address of Submitting Author

marco.taddei@unipi.it

Institution

Paul Scherrer Institute - Università di Pisa

Country

Switzerland - Italy

ORCID For Submitting Author

0000-0003-2805-6375

Declaration of Conflict of Interest

No conflict of interest to report.

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