Powder diffraction study of zeolitic imidazolate framework-8

$Page 1: Powder diffraction study of zeolitic imidazolate framework-8$

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

Powder Diffraction Study of Zeolitic Imidazolate Framework-8

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A. Petricola, 2008. Ariel view of the ESRF, Available from: http://www.esrf.eu/decouvrir [Accessed on 13/01/2015]

http://www.esrf.eu/decouvrir

http://www.esrf.eu/decouvrir


ESRF – EUROPEAN SYNCHROTRON RADIATION FACILITY

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ESRF, 2008, ESRF brochure [online]. Grenoble: ESRF. Available from:http://www.esrf.fr/about/information-material/brochures [accessed on: 13/01/2015]

Linac

Booster Synchrotron

Storage Ring

l Title of Presentation l Date of Presentation l Author

SYNCHROTRON ANIMATION

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PXRD – POWDER X-RAY DIFFRACTION

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2θ

Synchrotron radiation (X-

rays) Powder Sample

Detector

I

ID22

• High resolution powder X-ray diffraction beamline.

• Insertion device used is an undulator:

• Also uses a monochromator.

Bragg’s Law

• Path length difference: AB+BC=2dsinθ

• When reflected waves are in phase, AB+BC=nλ

• This gives Braggs Law:

• Commonly shortened to:

ID22, Technical description [online], Grenoble, ESRF. Available from: http://www.esrf.fr/id22/technical-description [accessed on: 21/01/2015] P.Atkins, J. De Paula; Atkins’ Physical Chemistry; OUP, Oxford, Ninth edn., 2010, 701-704

A

B

C

θ

θ

d

http://www.esrf.fr/id22/technical-description

http://www.esrf.fr/id22/technical-description


PLACEMENT OBJECTIVES

• Research current MOF and ZIF chemistry• Synthesise ZIF 8 using a range of methods• Use PXRD as a characterisation technique• Gas adsorption study of ZIF 8

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Unit cell of ZIF 8 showing pore opening comprised of 6-methylimidazole rings


INTRODUCTION TO MOFS AND ZIFS

• Metal organic frameworks or MOFs are comprised of metal ions or clusters coordinated to organic molecules

• Zeolitic imidazolate frameworks or ZIFs are a subclass of MOFs. They are made of transition metal ions and imidazolate organic linkers.

• ZIFs have structures analogous to those of naturally occurring alluminosilicate zeolites. M-Im-M (where M represents the transition metal ion) angle is similar to that of the 145o Si-O-Si found in zeolites.

• MOFs and ZIFs are highly porous with large surface areas and hence have potential applications in gas storage and catalysis.

• ZIFs have particularly high chemical and thermal stability.

• ZIF 8 is Zn2+ ions with 2-methylimidazole linkers. It takes the form Zn(mIm)2

• ZIF 8 has the space group I3m (no.217)

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DIFFERENT SYNTHETIC METHODS

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Solvothermal• Reagents are a hydrated metal salt and the

chosen imidazole linker• Organic solvents or alcohols • High yields and near stoichiometric ratio of

ragents• More expensive and more difficult to dispose of

solvents etc…

Hydrothermal• Reagents are a hydrated metal

salt and the chosen imidazole linker

• Water as solvent• More environmentally friendly

option• Requires a large excess of the

linker molecule

Dimethylformamide (DMF) method1:• Zn(NO3)2∙6H2O (14mmol), 2-methylimidazole

(11.7mmol)• Heated in a programmable oven• Precipitate collected by filtrationEthanol/Acetone method2:• Zn(NO3)2•6H2O and 2-methylimidazole (1:8 molar ratio)• Precipitate collected by centrifugation

1. K.S. Park, Z. Ni, A.P. Côté, J.Y. Choi, R. Huang, F.J. Uribe-Romo, H.K. Chae, M. O’Keeffe, O.M. Yaghi; Proceedings of the National Academy of Sciences of the United States of America; 2006; vol. 103 no. 27; 10186-101912. E.L. Bustamante, J.L. Fernández, J.M. Zamaro; Journal of Colloid and Interface Science; 2014; vol. 424; 37-433. K. Kida, M. Okita, K. Fujita, S. Tanaka, Y. Miyake; CrystEngComm; 2013; vol. 15 no. 9; 1794-1801

Aqueous method3:• Used Zn(NO3)2•6H2O (2.5mmol) and 2-

methylimidazole (25mmol)• Heated in a programmable oven• Precipitate collected by filtration


DIMETHYLFORMAMIDE (DMF) SYNTHESIS

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2θ

I

• λ = 0.496Å• 0.9mm capillary• Indexed using DASH 3.2 to give a cubic unit cell with lattice parameter 17.032Å• Simulated pattern lattice parameter 16.991Å

OG1b diffraction pattern collected on ID22

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0

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30

40

50

60

70

80

90

100

10 20 30

Intensity

2-theta

ZIF 8 cubic (Sim) Observed Reflections Empirical with Pawley refinement Simulated ZIF 8 pattern*

*K.S. Park, Z. Ni, A.P. Côté, J.Y. Choi, R. Huang, F.J. Uribe-Romo, H.K. Chae, M. O’Keeffe, O.M. Yaghi; Proceedings of the National Academy of Sciences of the United States of America; 2006; vol. 103 no. 27; 10186-10191


DMF ANALYSIS – PAWLEY REFINEMENT

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Section of jEdit file with ZnO structural information

2θ

I

Pawley refinement including ZnO structural information

• Impurity is ZnO• Can be accounted for using ZnO .cif file• Pawley refinement run in TOPAS using input file

from jEdit• Unit cell parameter refined to 17.016Å


DMF ANALYSIS – RIETVELD REFINEMENT

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2-methylimidazole z-matrix

OG1 diffraction pattern with Reitveld refinement ZIF-8 structure

• Rietveld refinement uses structural information to fit the pattern.• All peaks are fit • Sharp peaks show the sample is highly crystalline.

Z matrices• Rigid body• Defines the position of certain

atoms with respect to others• Uses a combination of bond

lengths and angles• In this case, 2-methylimidazole

has been defined using a z-matrix

I

2θ

2-methylimidazole rigid body


AQUEOUS SYNTHESIS AND ANALYSIS

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I

2θ

• Using the example of OG2. λ = 0.401Å. 1.0mm capillary.• Indexed using DASH 3.2 to give an orthorhombic unit cell with parameters: a= 24.057Å, b= 19.673Å, c=

16.983Å. • Space group P222 was used for Pawley refinement.• It is clearly not ZIF 8.

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0

10

20

30

40

50

60

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10 20 30

Intensity

2-theta

ZIF 8 cubic (Sim) Observed Reflections

Simulated

Empirical


ETHANOL/ACETONE SYNTHESIS AND ANALYSIS

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2θ2θ

I I

• λ=0.345Å. 1.0mm capillary• Indexed to give lattice

parameter 16.991Å • Pawley and Rietveld

refinement run using space group I4̅3m

• Lattice parameter refined to 16.581Å

Ethanol with Rietveld

Acetone with Rietveld

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0

10

20

30

40

50

60

70

80

90

100

10 20 30

Intensity

2-theta

ZIF 8 cubic (Sim) Observed Reflections

Simulated

• λ=0.345Å. 1.0mm capillary

• Indexed to give lattice parameter 17.006Å

• Pawley and Rietveld refinement run using space group I4̅3m

• Lattice parameter refined to 16.619Å


COMPARISON OF SYNTHETIC METHODS

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Synthetic method DMF Aqueous Ethanol/Acetone

Lattice type Cubic Orthorhombic Cubic

Space group I4̅3m P222 I4̅3m

Lattice parameter(s), (Å)

a=b=c=17.016 a=24.057, b=19.673, c=16.983 a=b=c=16.581 (ethanol)a=b=c=16.619 (acetone)

Diffraction Pattern

2θ

I Ethanol

2θ

I Acetone

I

2θ

I

2θ


GAS ADSORPTION STUDY/PLANS FOR GAS ADSORPTION STUDY

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• CO2 adsorbed onto sample at various pressures• Analysis will be to try and understand where the molecules lie in the framework• Will look to do further measurements with other gases.


CONCLUSION SO FAR AND PLANS FOR REST OF THE PLACEMENT

Conclusions• Wide range of synthetic routes• DMF method was most suitable for this study:• Sharp peaks

• Correct lattice parameter

• Uses sensible amounts of reagents

• Gas adsorption• Initial look shows gas was adsorbed into the pores

Future Plans• Further gas adsorption measurements• Repeat measurements

• Further measurements with different gases

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ACKNOWLEDGEMENTS

• ESRF – European Synchrotron Radiation Facility• In particular:• Christina Drathen

• Andy Fitch

• All the staff on ID22

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PROBLEMS FACED SO FAR…

• Samples had a very short lifetime in the beam.

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3 three minute scans run at the same position on the capillary

ZnO peak (left) with and ZIF 8 peak (right)


WHAT IS A SPACE GROUP?

• Categories developed by mathematical group theory• Describe the symmetry elements for unit cells

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Powder diffraction study of zeolitic imidazolate framework-8