Intermediates in the Synthesis of Zr-Based Metal-Organic Framework UiO-66 [post]

Marco Taddei, Jeroen A. van Bokhoven, Marco Ranocchiari
2019 unpublished
We recently discovered that aging a solution of zirconium(IV) tetrachloride (ZrCl<sub>4</sub>) 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 [<i>Chem. Commun.</i> <b>2016</b>, <i>52</i>, 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
more » ... and structural characterization of a microcrystalline zirconium-based compound of formula [ZrCl(OH)<sub>2</sub>(DMF)<sub>2</sub>]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)<sub>2</sub>(DMF)<sub>2</sub>]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 ZrCl<sub>4</sub> as the Zr(IV) source. By starting from ZrCl<sub>4</sub> and generating [ZrCl(OH)<sub>2</sub>(DMF)<sub>2</sub>]Cl in situ in solution through aging, we obtained smaller crystallites as the aging time increased, proving that [ZrCl(OH)<sub>2</sub>(DMF)<sub>2</sub>]Cl plays a role in the aging process. The possible role of [ZrCl(OH)<sub>2</sub>(DMF)<sub>2</sub>]Cl in the crystallization mechanism of UiO-66 is also discussed.<br>
doi:10.26434/chemrxiv.11382165 fatcat:ovasnakwhncqbor6cspruuomd4