Three-dimensional crystal structure of novel aluminophosphate PST-5 solved using a powder charge flipping method

Abstract

Novel PST-5 which resists structure solution has been solved using a powder charge flipping method.

Synthesis and Characterization of Silicoaluminophosphate CIT-16P and Its Transformation to SAPO-17

“…The 31 P MAS NMR spectrum of as-synthesized CIT-16P showed two groups of signals in the regions of −9 to −14 ppm and −20 to −30 ppm, the former, which disappear after thermal treatment, suggests the presence of partially OHcoordinated P-sites. 14 The thermally treated CIT-16P showed only two resonances at −29.1 and −34.7 ppm in the 31 P NMR spectrum, which is consistent with tetrahedrally connected and dehydrated AlPO 4 -or SAPO-17 results. 20,24 The single resonance (Figure 3c) in the 29 Si CPMAS NMR spectrum at ca.…”

“…15,16 One such example that demonstrates this difficulty is an organic−AlPO 4 hybrid material, PST-5, which transforms to PST-6 (PSI) following the removal of the organic structure-directing agent (OSDA). 14 Here, we demonstrate the synthesis of a new SAPO material (designated herein as CIT-16P, Figure 1a) that transforms into SAPO-17 (ERI) when the OSDA is removed. Diquinuclidinium-based diquats with C 3 − or C 4 − linkers (Figure 1b), which are OSDAs known to crystallize ERI-, 17 AFX-, 18 and SATtype 19 molecular sieves, crystallized CIT-16P, albeit in a very narrow range of synthesis parameters.…”

“…The coordinations of Al, P, and Si in the as-synthesized CIT-16P and resultant SAPO-17 materials were investigated by solid-state NMR spectroscopy (Figure a–c). As-synthesized CIT-16P showed two broad signals in its 27 Al MAS NMR spectrum at 41.5 and 7.3 ppm that can be attributed to tetrahedral and pentacoordinated Al species, respectively. ,,, The 7.3 ppm 27 Al signal survived cycles of extensive ethanolamine washing steps (Figure S6), suggesting that this signal is unlikely from extracrystalline Al-containing species, but rather from Al sites bound within the framework. The population of these nontetrahedral Al sites is significant in the framework of CIT-16P .…”

“…Compared to their zeolitic counterparts, structures of AlPO 4 -based molecular sieves can be more challenging to analyze based on X-ray or electron-beam diffractometry techniques due to their structural instability or complex coordination behaviors of T-sites. For instance, the Al- or P-sites of the AlPO 4 framework can form extra coordination bonds with OH – /H 2 O or occluded organic molecules. , One such example that demonstrates this difficulty is an organic–AlPO 4 hybrid material, PST-5, which transforms to PST-6 (PSI) following the removal of the organic structure-directing agent (OSDA) …”