Influence of Water in the Synthesis of the Zirconium-Based Metal–Organic Framework UiO-66: Isolation and Reactivity of [ZrCl(OH)2(DMF)2]Cl
journal contribution
posted on 2020-05-14, 16:11 authored by Marco Taddei, Jeroen A. van Bokhoven, Marco RanocchiariWe recently discovered
that aging a solution of zirconium(IV) tetrachloride
(ZrCl4) in N,N-dimethylformamide
(DMF) in the presence of water, followed by the addition of a 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
on 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
the 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 a 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.
