These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
Preprints are manuscripts made publicly available before they have been submitted for formal peer review and publication. They might contain new research findings or data. Preprints can be a draft or final version of an author's research but must not have been accepted for publication at the time of submission.
revised on 03.04.2020 and posted on 06.04.2020by 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.