Electron Paramagnetic Resonance

Mendt, Matthias; Šimėnas, Mantas; Pöppl, Andreas

doi:10.1002/9783527693078.ch21

Cited by 9 publications

(8 citation statements)

References 86 publications

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“…Typically, the magnetic properties of MOFs have mainly been investigated by magnetic susceptibility measurements. ,,,, However, recently, electron paramagnetic resonance (EPR) spectroscopy has been more widely applied in this field, as it may provide complementary information about the paramagnetic ions and their magnetic coupling on a microscopic scale. ,,, However, EPR is traditionally employed for investigations of paramagnetic ions in magnetically diluted materials where the various magnetic interactions can be fully resolved. In that way, in a previous electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) study we have explored the coordination state of cupric ions in the magnetically diluted mixed-metal MOF ∞ 3 [Cd 0.98 Cu 0.02 (prz–trz–ia)] and determined their magnetic interaction tensors .…”

Section: Introductionmentioning

confidence: 99%

Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound _∞³[Cu(prz–trz–ia)]

et al. 2018

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Multifrequency electron paramagnetic resonance (EPR) spectroscopy, magnetic susceptibility measurements, and density functional theory (DFT) have been employed to characterize the magnetic properties of Cu 2+ ions and their magnetic interactions in the porous metal−organic framework compound ∞ 3 [Cu(prz−trz−ia)]. Two distinct cupric ion species were found to contribute to the overall magnetic susceptibility of the polycrystalline material. The majority of the copper ions forms antiferromagnetically coupled ion pairs located at framework sites in the dinuclear metal ion units of this coordination polymer. Their theoretically computed isotropic intrapair exchange coupling constant J 1 = −26 cm −1 is in excellent agreement with experimentally determined exchange coupling. Besides the metal ion pairs, a part of the copper in this material is present as agglomerates of additional framework ions.

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Section: Introductionmentioning

confidence: 99%

Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound _∞³[Cu(prz–trz–ia)]

et al. 2018

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“…EPR spectroscopy has not yet become a routine tool for studying MOFs; however, its applications in this field are rapidly developing. 40 − 42 Bare MOFs with paramagnetic metals, embedded or adsorbed radicals, were actively studied over the past decade. 10 , 43 − 45 In particular, structural transitions in flexible MOFs such as MIL-53 and some others, were addressed.…”

mentioning

confidence: 99%

“…EPR spectroscopy has not yet become a routine tool for studying MOFs; however, its applications in this field are rapidly developing. − Bare MOFs with paramagnetic metals, embedded or adsorbed radicals, were actively studied over the past decade. ,− In particular, structural transitions in flexible MOFs such as MIL-53 and some others, were addressed. ,− Several promising applications of in situ EPR to MOFs were recently reported, − including a study of Cu-doped DUT-8(Ni) . DUT-49(Cu), to the best of our knowledge, was never studied using EPR.…”

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confidence: 99%

Structural Transitions of the Metal–Organic Framework DUT-49(Cu) upon Physi- and Chemisorption Studied by in Situ Electron Paramagnetic Resonance Spectroscopy

Polyukhov

Krause

Bon

et al. 2020

J. Phys. Chem. Lett.

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Flexible metal–organic frameworks (MOFs) exhibit a variety of phenomena attractive for basic and applied science. DUT-49(Cu) is one of the remarkable representatives of such MOFs, where phase transitions are coupled to pressure amplification and “negative gas adsorption”. In this work we report important insights into structural transitions of DUT-49(Cu) upon physi- and chemisorption of gases and volatile liquids obtained by in situ electron paramagnetic resonance (EPR) spectroscopy. In this method, phase transitions are detected via the zero-field splitting in dimeric copper(II) units. First, a new approach was validated upon physisorption of n -butane. Then, using diethyl ether, we for the first time demonstrated that chemisorption can also trigger phase transition in DUT-49(Cu). On the basis of the EPR results, the transition appears completely reversible. The developed EPR-based approach can also be extended to other flexible MOFs containing paramagnetic metal paddlewheels, where high sensitivity and spectral resolution allow in situ studies of stimuli-induced structural variability.

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“…One of the best approaches to monitor penetration of guest molecules into the porous material relies on the probes located inside the pores. − Therefore, we developed a synthesis of ZIF-8 with embedded stable nitroxide radicals, which are excellent reporters for the electron paramagnetic resonance (EPR) spectroscopy and can be used in low concentrations such as 1 per 1000 MOF cavities or less . Briefly, stable nitroxide TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) was added to a solution of 2-methylimidazole during the common synthesis of ZIF-8 in water (details in Supporting Information, SI).…”

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Precise Measurement and Controlled Tuning of Effective Window Sizes in ZIF-8 Framework for Efficient Separation of Xylenes

et al. 2019

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Metal−organic frameworks (MOFs) are the promising nanomaterials for separation of molecules with close dimensions and structures, such as various types of isomers. The efficiency of separation can be greatly enhanced if the apertures of the nanosized windows, controlling the diffusion of a particular molecule inside the cavities, are fine-tuned by external stimuli. We report the new approach for precise measurement of window sizes in ZIF-8 MOF and employ it in efficient separation of xylenes, which is of high practical importance. For this sake, we synthesized ZIF-8 with embedded stable nitroxides in the pores and applied electron paramagnetic resonance spectroscopy for in situ kinetic measurement of the diffusion of various guest molecules through the material. Slight variation of temperature within 298−333 K allowed tuning of the windows and reaching optimum conditions for separation of p-, m-, and o-xylenes with the efficiency up to 92−95%. The developed methodology provides deeper understanding of steric and kinetic aspects of molecular diffusion in ZIF-8 and paves the way to rational optimization of other MOF-based separation applications.

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Electron Paramagnetic Resonance

Cited by 9 publications

References 86 publications

Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound _∞³[Cu(prz–trz–ia)]

Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound _∞³[Cu(prz–trz–ia)]

Structural Transitions of the Metal–Organic Framework DUT-49(Cu) upon Physi- and Chemisorption Studied by in Situ Electron Paramagnetic Resonance Spectroscopy

Precise Measurement and Controlled Tuning of Effective Window Sizes in ZIF-8 Framework for Efficient Separation of Xylenes

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Electron Paramagnetic Resonance

Cited by 9 publications

References 86 publications

Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound ∞3[Cu(prz–trz–ia)]

Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound ∞3[Cu(prz–trz–ia)]

Structural Transitions of the Metal–Organic Framework DUT-49(Cu) upon Physi- and Chemisorption Studied by in Situ Electron Paramagnetic Resonance Spectroscopy

Precise Measurement and Controlled Tuning of Effective Window Sizes in ZIF-8 Framework for Efficient Separation of Xylenes

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Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound _∞³[Cu(prz–trz–ia)]

Multifrequency EPR, SQUID, and DFT Study of Cupric Ions and Their Magnetic Coupling in the Metal–Organic Framework Compound _∞³[Cu(prz–trz–ia)]