In this study the high-pressure (HP) behavior of a synthetic potassium alluminosilicate zeolite L (ZL) [1] has been investigated by in situ powder synchrotron X-ray diffraction, using the “penetrating” media 16:3:1 methanol:ethanol:water (m.e.w.) mixture as P-transmitting fluids. ZL is an interesting and well know porous system used to crate organic-inorganic hybrid microporous materials [2,3] currently applied in strategic areas, from sustainable energy technologies to biomedical sciences. In fact this investigation is a preparatory study to exploit the effect of high pressure on hybrid ZL composite materials. The HP experiments were performed from ambient pressure (Pamb) to 6.25 GPa and some patterns were also collected upon decompression to Pamb. The evolution of the unit cell parameters of the ZL were followed by the Rietveld profile fitting up to the highest P, showing neither amorphisation nor phase transition from the original space group P6/mmm. ZL undergone to an anisotropic compression in fact the a axis is the most rigid axis (-0.9%) whereas the c axis is the most compressible one (-4.1%).The pressure-induced water intrusion, as reported in literature for K or Rb-galliosilicate ZL [4,5] is also here observed. The over hydration effect is concentrated in the P range from Pamb to 4.5 GPa. The refined total number of water molecules per unit cell linearly increases from 18 to 36. No penetration of methanol and ethanol was observed. The H2O molecules are confined in the main 12 membered ring channel, distributed on seven independent crystallographic sites (in addition to the five already present in the original ZL structure, two new sites were found). The water molecules weakly interact with the ZL framework and with the extraframework K sites. On the contrary, they are strongly hydrogen-bonded each other. The water intrusion is completely reversible: upon P release, the cell parameters and the water content are recovered. These results - in agreement with those present in literature for other ZL samples with different chemical composition - indicate that the capacity of this system to incorporate nanostructures inside its channels is mainly driven by its peculiar one-dimensional spatial constrains. [1] Ch. Baerlocher, L.B. McCusker, D.H. Olson, Atlas of Zeolite Framework Types, 6th ed., Elsevier, Amsterdam, 2007 [2] L.Gigli, R.Arletti, G.Tabacchi, E. Fois, J. G. Vitillo, G. Martra, G. Agostini, S. Quartieri, G,Vezzalini J. Phys. Chem. C, 2014, 118 (29), 15732–15743. [3] L. Gigli, R. Arletti, J. G. Vitillo, G. Alberto, G. Martra, A. Devaux, and G. Vezzalini J. Phys. Chem. C, 2015, 119 (28), 16156–16165. [4] Y. Lee, C. C. Kao, S.J. Kim, H.H. Lee, D.R. Lee, T.J. Shin, and J.Y. Choi Chemistry of Materials 2007 19 (25), 6252-6257. [5] Y. Lee, S.J. Kim, D.C. Ahn, and N.S. Shin Chemistry of Materials 2007 19 (9), 2277-2282.

The high pressure-induced water intrusion in the 1-D K-aluminosilicate zeolite L: a synchrotron X-ray powder diffraction study

Simona Quartieri;
2017-01-01

Abstract

In this study the high-pressure (HP) behavior of a synthetic potassium alluminosilicate zeolite L (ZL) [1] has been investigated by in situ powder synchrotron X-ray diffraction, using the “penetrating” media 16:3:1 methanol:ethanol:water (m.e.w.) mixture as P-transmitting fluids. ZL is an interesting and well know porous system used to crate organic-inorganic hybrid microporous materials [2,3] currently applied in strategic areas, from sustainable energy technologies to biomedical sciences. In fact this investigation is a preparatory study to exploit the effect of high pressure on hybrid ZL composite materials. The HP experiments were performed from ambient pressure (Pamb) to 6.25 GPa and some patterns were also collected upon decompression to Pamb. The evolution of the unit cell parameters of the ZL were followed by the Rietveld profile fitting up to the highest P, showing neither amorphisation nor phase transition from the original space group P6/mmm. ZL undergone to an anisotropic compression in fact the a axis is the most rigid axis (-0.9%) whereas the c axis is the most compressible one (-4.1%).The pressure-induced water intrusion, as reported in literature for K or Rb-galliosilicate ZL [4,5] is also here observed. The over hydration effect is concentrated in the P range from Pamb to 4.5 GPa. The refined total number of water molecules per unit cell linearly increases from 18 to 36. No penetration of methanol and ethanol was observed. The H2O molecules are confined in the main 12 membered ring channel, distributed on seven independent crystallographic sites (in addition to the five already present in the original ZL structure, two new sites were found). The water molecules weakly interact with the ZL framework and with the extraframework K sites. On the contrary, they are strongly hydrogen-bonded each other. The water intrusion is completely reversible: upon P release, the cell parameters and the water content are recovered. These results - in agreement with those present in literature for other ZL samples with different chemical composition - indicate that the capacity of this system to incorporate nanostructures inside its channels is mainly driven by its peculiar one-dimensional spatial constrains. [1] Ch. Baerlocher, L.B. McCusker, D.H. Olson, Atlas of Zeolite Framework Types, 6th ed., Elsevier, Amsterdam, 2007 [2] L.Gigli, R.Arletti, G.Tabacchi, E. Fois, J. G. Vitillo, G. Martra, G. Agostini, S. Quartieri, G,Vezzalini J. Phys. Chem. C, 2014, 118 (29), 15732–15743. [3] L. Gigli, R. Arletti, J. G. Vitillo, G. Alberto, G. Martra, A. Devaux, and G. Vezzalini J. Phys. Chem. C, 2015, 119 (28), 16156–16165. [4] Y. Lee, C. C. Kao, S.J. Kim, H.H. Lee, D.R. Lee, T.J. Shin, and J.Y. Choi Chemistry of Materials 2007 19 (25), 6252-6257. [5] Y. Lee, S.J. Kim, D.C. Ahn, and N.S. Shin Chemistry of Materials 2007 19 (9), 2277-2282.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/3120109
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