Callens, Freddy

Depauw, Hannes

Leus, Karen

Nevjestic, Irena

Van Der Voort, Pascal

Vrielinck, Henk

English

Ghent University Academic Bibliography

VIV Ions As Paramagnetic Probes For Monitoring the Structural Flexibility ofV-Doped MIL-53(Al)Irena Nevjestic´(1), Hannes Depauw(2), Karen Leus(2), Pascal Van Der Voort(2), Freddy Callens(1), Henk Vrielinck(1)(1) Ghent University, Dept. of Solid State Sciences, Krijgslaan 281-S1, B-9000 Gent, Belgium(2) Ghent University, Dept. of Inorganic and Physical Chemistry, COMOC, Krijgslaan 281-S3, B-9000 Gent, BelgiumIntroductionI Metal-organic frameworks (MOFs) are crystalline porousmaterials constructed from metal moieties connected by organicligandsI Many interesting features: well-defined pore size, pore shape,ultra-high porosity, ...I Their tunability in porosity and in functionalization of the internalsurface makes MOFs an important class of materials withpotential major impact in catalysis, gas sensing and gas storageI MIL-53(Al) [Al(OH)(BDC)] [1]BDC = terephthalate or 1,4-benzenedicarboxylateMIL = Mate´riaux de l’Institut LavoisierI After synthesis, in the MIL-53(Al)AS the channels are filled withuncoordinated BDC moleculesI These can be removed by calcination or solvent extraction, whichis referred to as activation of the MOFI Activated MIL-53(Al) exhibits a structural flexibility, referred to asbreathing: the structure can reversibly change from a large openpore (LP) to a narrow pore (NP) form without any loss ofcrystallinityTwo VIV states in activated V-doped MIL-53(Al)I Temperature-triggered breathing was investigated in MIL-53(Al) doped withVIV ions (3d1, S = 1/2) ionsI Powder EPR spectra of activated 1.5% V-doped MIL-53(Al) in vacuum atroom temperature (RT) are shown in NP and LP states280 300 320 340 360 380 400 420B(mT)T>373 KStoring in liquid N2LPNPCarbonOxygenAluminumVanadiumLP stateNP stateMixture of LP and NP stateI EPR spectra of VIV in NP and LP MIL-53(Al) are clearly differentI VIV is paramagnetic probe for detecting the phase transition in the frameworkEPR insets show a magnification of the high-field part of the spectraBreathing effect monitored in situ in vacuum4 6 10 5 9 11 (200) (110) (400) (220) (110) (200) (220) (121) (011) (321) NP LP LP d – spacing (Å) 8 7 0 1 -1 (111 )  Temperature (K) 300 300 350 400 450 400 350 in situ XRD EPR insets show a magnification of the high-field part of the spectraXRD λ = 0.825086 A˚, 2θ is converted to d-spacing in A˚ via Bragg’s law. Miller indices are indicated for both the NP (below) and LP (above) state. Thesample was at RT in the NP state, after the heating cycle the XRD pattern of the LP state is observed. [2]Breathing effect monitored in situ in air4 6 10 5 9 11 (200) (110) (400) (220) (110) (200) (220) (121) (011) (321) NP NP LP d – spacing (Å) 8 7 0 1 -1 (111 )  Temperature (K) 300 300 350 400 450 400 350 in situ XRD EPR insets show a magnification of the high-field part of the spectraXRD λ = 1.54056 A˚, 2θ is converted to d-spacing in A˚ via Bragg’s law. Miller indices are indicated for both the NP (below) and LP (above) state. Thesample was at RT in the NP state, at approximately 425 K full transition to the LP state occurred. Cooling down the sample to RT, the XRD pattern of theNP state starts appearing again. [2]X-ray absorption near edge structure (XANES) and EPR3.4 3.54.13.5 3.44.200.511.522.533.544.55Oxidation state of V-doped MIL-53 determined from XANESOxidation stateI Position of mainedge peak definesionizationthreshold tocontinuum statesI Main edge peakshifts to higherenergy withincreasedoxidation stateI Afteractivationincrease inconcentra-tion of VIVions isobservedin EPRspectrumConclusionsI The EPR spectra of VIV in the NP and LP MIL-53(Al) states are clearly distinguishableI The EPR active VIV ions (3d1, S = 1/2) can be used as a local probe to detect the phase transitions in the frameworkI Oxidation states of V-doped MIL-53 determined with XANES is in agreement (within error) with EPR quantitative measurementsReferences :[1] T. Loiseau et al., Chem.-Eur. J., 2004, 10 (6), 1373-1382.[2] I. Nevjestic´ et al., J. Phys. Chem. C, 2016, 120 (31), 17400-17407.Acknowledgments :Diamond Light Source (I11), CoCooNresearch group, Pieter Tuck (XANESanalysis), Luka LuketinContact :Irena Nevjestic´Ghent University, Dept. of Solid State SciencesKrijgslaan 281-S1, B-9000 Gent, BelgiumE-mail: Irena.Nevjestic@UGent.be

VIV ions as paramagnetic probe for monitoring the structural flexibility of V-doped MIL-53(Al)

https://biblio.ugent.be/publication/8086942/file/8087035.pdf

VIV ions as paramagnetic probe for monitoring the structural flexibility of V-doped MIL-53(Al)

Abstract

Similar works

Full text

Available Versions

Ghent University Academic Bibliography