The influence of the framework and extraframework content on the high pressure behavior of the GIS type zeolites: the case of amicite

We report the results of a study [1], performed by in-situ synchrotron X-ray powder diffraction, of the high pressure behavior of the natural zeolite amicite [K4Na4(Al8Si8O32)•10H2O], the GIS-type phase with ordered (Si, Al) and (Na, K) distribution. The experiments were carried out at the SNBL1 (BM01a) beamline at ESRF, up to 8.13(5) GPa in methanol:ethanol:water = 16:3:1 (m.e.w.), and 8.68(5) GPa in silicone oil (s.o.).The crystal structure refinements of the patterns collected in m.e.w. were performed up to 4.71(5) GPa, while for the patterns collected in s.o. only the unit cell parameters were determined as a function of pressure. The observed framework deformation mechanism—similar to that reported for the other studied phases with GIS topology—is essentially driven by the distortion of the “double crankshaft” chains and the consequent changed shape of the 8-ring channels . However, the degree of compressibility is strongly dependent on the chemical compositions of the porous phases. The comparison with the high pressure behavior of the other GIS-type phases confirms that the compressibility of microporous materials is not simply related to their framework density and topology, but is also greatly affected by the type, amount, and location of the extra-framework species. The pressure-induced over-hydration observed in the experiment performed in aqueous medium (m.e.w.) occurs without unit cell volume expansion, and is substantially reversible upon pressure release. [1] R. Arletti, C. Giacobbe, S. Quartieri, G. Vezzalini, Minerals 2017, 7, 18; doi:10.3390/min7020018.