It has previously been shown that there are many benefits to be obtained in combining several techniques in one in situ set-up to study chemical processes in action. Many of these combined set-ups make use of two techniques, but in some cases it is possible and useful to combine even more. A set-up has recently been developed that combines three X-ray-based techniques, small- and wide-angle X-ray scattering (SAXS/WAXS) and quick-scanning EXAFS (QEXAFS), for the study of dynamical chemical processes. The set-up is able to probe the same part of the sample during the synthesis process and is thus able to follow changes at the nanometre to micrometre scale during, for example, materials self-assembly, with a time resolution of the order of a few minutes. The practicality of this kind of experiment has been illustrated by studying zeotype crystallization processes and revealed important new insights into the interplay of the various stages of ZnAPO-34 formation. The flexibility of this set-up for studying other processes and for incorporating other additional non-X-ray-based experimental techniques has also been explored and demonstrated for studying the stability/activity of iron molybdate catalysts for the anaerobic decomposition of methanol.
We report on the direct observation of key organic template−framework interactions leading to the formation of specific aluminophosphate structures. In particular, we show how MeAPO-34 formation was governed by an interaction between the divalent framework substituted metal ion and the template conformation, while for AlPO-5 the structure formation was determined by the template conformation alone. Understanding such interactions therefore appears to be important for the rationalization of microporous material formation.
Crystalline inorganic solids show intriguing properties of importance in many technological applications, such as ferromagnetism, semiconductivity, gas sensing, and catalysis. A great deal of attention has been and continues to be focused on understanding why these materials possess these properties. When such phenomena are fundamentally understood, it becomes possible to improve their performance, and this can potentially lead to the development of new "designer" materials to meet the challenges of the future. However, the concept of a designer solid is still some way from being realized since the critical stages of inorganic solid crystallization are still not sufficiently understood.Time-resolved in situ experimentation represents the most likely means by which the key stages of inorganic solid crystallization can be unraveled. Many studies using a variety of analytical techniques on a range of samples have been reported in the literature with the area of microporous material crystallization receiving a lot of attention. 1-3 However, such studies often focus on data acquired using a single technique, which rarely provides all of the necessary information from which new insight can be obtained. This is because changes occur over the molecular (local coordination state), nano (primary units), and microscale (crystallite formation) dimension during crystallization, whereas the techniques are often only able to probe limited size regimes. In other words, with separate in situ studies, it is sometimes difficult to obtain consistent and corroborative information. One way to overcome these limitations is to intelligently combine complementary techniques into one experimental setup, and this approach often yields new insight. Some examples include the observation of primary units in zeolite MFI formation and the importance of a coordination state change of Co 2+ before the formation of CoAlPO-5 molecular sieves. 2,4 In addition, a combination of techniques has several advantages. 5 One being the possibility to evaluate if the probing technique may influence the state of a sample. Furthermore, you circumvent the need to repeat identical experimental conditions for recording separate measurements; although seemingly a trivial point, it is far from easy to achieve experimentally.In this communication, we present a novel setup, which combines SAXS, WAXS, and XAFS to study the crystallization processes of inorganic solids in depth. This study aims to follow the changes that occur with time at the molecular, nanoscopic, and crystalline level, with a time resolution in the order of a few minutes. The setup enables us to observe the various stages of zinc-substituted microporous aluminophosphate formation in one experiment and represents, to the best of our knowledge, the first data of its kind acquired in such a manner. A scheme of the setup is given in Figure 1. In Figure 2, we show the raw data collected during the heating of the zinc-doped aluminophosphate gel. Data analysis suggested that the initial † Utrecht Univers...
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