Infrared Spectroscopy 75

Infrared spectroscopy was measured using a PerkinElmer® Spectrum™ 100 FTIR with an Attenuated Total Reflectance (ATR) attachment. Spectra were acquired at 4 cm-1 resolution in the range 4000-550 cm-1.

2.4.2

Thermogravimetric Analysis

Thermogravimetric (TG) data were recorded using a Mettler Toledo TGA/DSC1 instrument. Approximately 10 mg of powder were loaded into an alumina crucible; the sample was heated in air to 1000 °C at a rate of 10 °C min-1. Room temperature experiments were also performed where the adsorption of volatile organic vapours was followed in situ. Nitrogen gas was passed through a Drechsel bottle containing a liquid organic which was then passed through the sample chamber.

For all of the TGA results where the empirical formula was known the first order and second order difference curves were used to identify small plateaus and inflection points in the data. The first order difference is calculated using Equation 2.7.

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[ ] [ ] [ ]

Equation 2.7

When the first order difference is close to zero it indicates that there is little change in the mass of the sample. The second order difference curve, calculated using Equation 2.8, was used to identify the inflection points in the data.

_{[ ] [ ] [ ]}

Equation 2.8

An inflection point is defined as the point at which the curvature of the graph changes sign from positive to negative or vice versa. Only the inflection points where the curvature changes sign from positive to negative, which indicates the onset of an increase in the rate of decomposition, were clearly marked on the graphs and used to predict the mass loss for each step.

- 77 - For all of the TGA results where the full empirical formula was not certain, i.e. the identity and quantity of the guest molecules was unknown, predictions were made based on the final mass of the metal oxide after complete decomposition; the mass, and consequently the number of moles, of the metal oxide was used to calculate theoretical masses of predicted empirical formulae. These masses were converted to percentage masses by dividing by the initial mass of the experimental sample. The predicted percentage masses were clearly marked on the graphs and compared to the percentage masses that correspond to the plateaus seen in the experimental data.

2.4.3

Elemental Analysis

All elemental analysis was carried out by MEDAC Ltd. The elements that were studied include C, H, N, S, F, and various metals.

2.4.4

UV/Vis Spectroscopy

Dimethylformamide was used as the solvent for the organic molecules studied using UV/Vis spectroscopy. Spectra were recorded using a Varian Cary® 50 UV-VIS-NIR spectrophotometer from Agilent Technologies in the range of 300 - 800 nm. The scan rate was 60 nm min-1.

2.4.5

Magnetic Studies

Magnetic studies were carried out using a superconducting quantum interference device known as a SQUID. The device used for these studies was a 5 T Quantum Design MPMS-5S SQUID Magnetometer capable of making measurements in the temperature range of 1.8 K to 400 K. Approximately 10 – 25 mg of sample were used for each experiment. Experiments to investigate the temperature dependence of the magnetisation were performed in a 0.01 T field in the range 2 – 400 K. The field dependence experiments were performed at four different temperatures; 5 K and 300 K

- 78 - were studied for each sample whereas the other two temperatures were chosen based on the features seen in the M vs T experiments. Data were recorded by H. Y. Playford and L. M. Daniels.

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2.5

References

1. R. M. Barrer, Hydrothermal Chemistry of Zeolites, Academic Press, London, 1982. 2. K. Byrappa and M. Yoshimura, Handbook of Hydrothermal Technology, William

Andrew, 2008, vol. 1

3. C. N. R. Rao, P. J. Thomas and G. U. Kulkarni, Nanocrystals: Synthesis, Properties and Applications, Springer, 2007, vol. 95

4. A. Rabenau, Angew. Chem. Int. Ed., 1985, 24, 1026-1040. 5. C. S. Cundy and P. A. Cox, Chem. Rev., 2003, 103, 663-702.

6. D. R. Modeshia and R. I. Walton, Chem. Soc. Rev., 2010, 39, 4303-4325.

7. A. Gaona-Gómez and C.-H. Cheng, Microporous Mesoporous Mater., 2012, 153, 227- 235.

8. X. Yang, I. D. Williams, J. Chen, J. Wang, H. Xu, H. Konishi, Y. Pan, C. Liang and M. Wu, J. Mater. Chem., 2008, 18, 3543-3546.

9. A. Michailovski, R. Kiebach, W. Bensch, J.-D. Grunwaldt, A. Baiker, S. Komarneni and G. R. Patzke, Chem. Mater., 2006, 19, 185-197.

10. H. Wu, D. Liu, H. Zhang, C. Wei, B. Zeng, J. Shi and S. Yang, Carbon, 2012, 50, 4847-4855.

11. M. T. Weller, Inorganic Materials Chemistry, 2nd edn., Oxford University Press, 1996. 12. A. Clearfield, J. Reibenspies and N. Bhuvanesh, eds., Principles and Applications of

Powder Diffraction, 1st edn., Wiley, 2008.

13. JCPDS. International Center for Diffraction Data, PA, USA, 2008.

14. A. C. Larson and R. B. Dreele, Los Alamos National Laboratory Report LAUR, 2000, 86, 748.

15. B. H. Toby, J. Appl. Crystallogr., 2001, 34, 210-213.

16. A. Le Bail, H. Duroy and J. L. Fourquet, Mater. Res. Bull., 1988, 23, 447-452. 17. N. Pienack and W. Bensch, Angew. Chem. Int. Ed., 2011, 50, 2014-2034.

18. E. Antonova, B. Seidlhofer, J. Wang, M. Hinz and W. Bensch, Chem. Eur. J., 2012, 18, 15316-15322.

19. A. T. Davies, G. Sankar, C. R. A. Catlow and S. M. Clark, J. Phys. Chem. B, 1997, 101, 10115-10120.

20. R. I. Walton, F. Millange, D. O'Hare, A. T. Davies, G. Sankar and C. R. A. Catlow, J. Phys. Chem. B, 2000, 105, 83-90.

21. F. Millange, R. El Osta, M. E. Medina and R. I. Walton, CrystEngComm, 2011, 13, 103-108.

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22. F. Millange, M. I. Medina, N. Guillou, G. Férey, K. M. Golden and R. I. Walton,

Angew. Chem. Int. Ed., 2010, 49, 763-766.

23. R. W. Cheary and A. A. Coelho, Programs XFIT and FOURYA, deposited in CCP14 Powder Diffraction Library, http://www.ccp14.ac.uk/.

24. S. J. Coles and P. A. Gale, Chem. Sci., 2012, 3, 683-689. 25. G. M. Sheldrick, Acta Crystallogr., 2008, A64, 112-122.

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Chapter 3

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3

Structural Transitions of MIL-53(Fe)

Studied in the Liquid Phase

This chapter details various in situ time-resolved energy dispersive X-ray diffraction (EDXRD) studies which have been used to investigate the adsorption properties of MIL-53(Fe). Initial studies include investigations to identify the conditions that can stabilise a transient crystalline phase which was observed in previous studies, by R. Walton and F. Millange,1 during the expansion of the framework in response to simple alcohols. The concentration and the rate of addition of the alcohol solutions were adjusted to identify the correct conditions to induce stabilisation. The studies into alcohol adsorption were then used as model behaviour when considering the adsorption of other guest molecules. This model behaviour was used to help investigate the industrially relevant problem of removing N/S heterocycles from petrochemicals. A combination of EDXRD data and adsorption isotherms were used to study the effect of guest concentration and solvent choice upon the ability of the framework to be able to adsorb these guest molecules. The various interactions between the host, the guests and the solvent were considered when exploring the differences in behaviour of the framework towards the different heterocycles.