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Issue 21, 2020
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Impact of dehydration and mechanical amorphization on the magnetic properties of Ni(ii)-MOF-74

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Abstract

Mechanically responsive metal–organic frameworks (MOFs) came very recently into the spotlight of material science for their unique properties and potential new fields of application. We present here a clarification of the magnetic properties of prototypical magnetic MOF-74 material, Ni(II)-MOF-74, using magnetization measurements, X-band electron spin resonance (ESR), multi-frequency high-field ESR (HF-ESR), and theoretical model. It was established that the guests populating the honeycomb channels have little influence on the magnetism of Ni-MOF-74, whereas magnetic properties change significantly upon mechanical amorphization. Amorphous material (am-Ni-MOF-74), which can be readily prepared by the mechanochemical treatment of dehydrated Ni-MOF-74 (deh-Ni-MOF-74), as shown by in situ monitoring methods, displays significantly lower bulk magnetization compared to Ni-MOF-74 and deh-Ni-MOF-74. This decline in magnetization is established to be a consequence of the spin-crossover from high-spin to a low-spin state of nickel(II) ions. The observed spin-crossover was rationalized by an insight into the changes of the nickel coordination sphere during the amorphization, which was provided by solid-state nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Additionally, it was found that am-Ni-MOF-74 behaves differently than its zinc analogue when exposed to vapors or liquid-additives in the milling process, indicating that the nature of the metal node plays a substantial role in the mechanical properties of this modular family of MOF materials.

Graphical abstract: Impact of dehydration and mechanical amorphization on the magnetic properties of Ni(ii)-MOF-74

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Article information


Submitted
18 Feb 2020
Accepted
20 Apr 2020
First published
20 Apr 2020

J. Mater. Chem. C, 2020,8, 7132-7142
Article type
Paper

Impact of dehydration and mechanical amorphization on the magnetic properties of Ni(II)-MOF-74

S. Muratović, B. Karadeniz, T. Stolar, S. Lukin, I. Halasz, M. Herak, G. Mali, Y. Krupskaya, V. Kataev, D. Žilić and K. Užarević, J. Mater. Chem. C, 2020, 8, 7132
DOI: 10.1039/D0TC00844C

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