Probing ZnAPO-34 Self-Assembly Using Simultaneous Multiple in Situ Techniques

The hydrothermal crystallization of ZnAPO-34 (CHA) molecular sieves has been studied for the first time using a combined in situ four technique setup utilizing SAXS/WAXS/XAFS/Raman to follow the various steps that occur during the complex transformation process of an amorphous precursor gel into a crystalline microporous material. These data are also supported by a detailed characterization of both the precursor gel (using Raman, NMR, XAFS, and TEM) and the final crystalline material (NMR, XRD, XAFS, TEM, and energy minimization calculations). Thus, all components during the various stages of reaction have been studied allowing for fundamental insight from the atomic/molecular level up to the bulk scale. On the basis of this multitechnique approach, the following observations are made: (i) The initial formation of a heterogeneous gel containing predominantly separate Al−O−P and Zn−O−P containing species as well as the presence of particles with a broad size distribution were noted. (ii) During sample heat...