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Cu2+ cations complexed by linear polyamines have been studied as structure-directing

The substitution of the divalent cations Mg 2+ and Zn 2+ into the aluminophosphate (AlPO) framework of STA-2 has been studied using an "NMR crystallographic" approach, combining multinuclear solid-state NMR spectroscopy, X-ray diffraction and firstprinciples calculations. Although the AlPO framework itself is inherently neutral, the positive charge of the organocation template in an as-made material is usually balanced either by the coordination to the framework of anions from the synthesis solution, such as OH  or F  , and/or by the substitution of aliovalent cations. However, the exact position and distribution of the substituted cations can be difficult to determine, but can have a significant impact upon the catalytic properties a material exhibits once calcined.   For as-made Mg substituted STA-2, the positive charge of the organocation template is balanced by the substitution of Mg 2+ for Al 3+ and, where required, by hydroxide anions coordinated to the framework. 27 Al MAS NMR spectra show that Al is present in both tetrahedral and five-fold coordination, with the latter dependent on the amount of substituted cations, and confirms the bridging nature of the hydroxyl groups, while high-resolution MQMAS spectra are able to show that Mg appears to preferentially substitute on the Al1 site. This conclusion is also supported by first-principles calculations.The calculations also show that 31 P chemical shifts depend not only on the topologicallydistinct site in the SAT framework, but also on the number of next-nearest-neighbour Mg species, and the exact nature of the coordinated hydroxyls (whether the P atom forms part of a six-membered ring, P(OAl)2OH, where OH bridges between two Al atoms). The calculations demonstrate a strong correlation between the 31 P isotropic chemical shift and the average bond angle. In contrast, for Zn substituted STA-2, both X-ray diffraction and NMR spectroscopy show less preference for substitution onto Al1 or Al2, with both appearing to be present, although that into Al1 appears slightly more favoured.

The use of copper polyamine complexes as structure directing agents for microporous solids offers a direct route to the inclusion of Cu 2+ complex cations in their pores: upon calcination, this gives active catalysts for the selective catalytic reduction of NO with NH 3. In situ synchrotron IR absorption spectroscopy on crystals of dimensions 25-35 μm has been used to monitor the dehydration of the Cu 2+-cyclam complex that acts as a co-template for the silicoaluminophosphate SAPO STA-7 and, at higher temperatures (400 °C), the calcination that gives the active catalyst Cu,H-SAPO STA-7. Polarised synchrotron IR microspectroscopy reveals strong alignment of N-H bonds of the Cu 2+ cyclam in the larger cages of as-prepared STA-7, and complementary X-ray diffraction, ESR and UV-visible spectroscopy and computer simulation indicates that hydrated complexes act as co-templates during crystallisation: dehydration leads to removal of their coordinated water by 200 °C.