The role of synchrotron radiation in examining the self-assembly of crystalline nanoporous framework materials: from zeolites and aluminophosphates to metal organic hybrids

Abstract

This tutorial review describes the role of synchrotron-based techniques in the study of the formation of Crystalline Nanoporous Framework Materials (CNFMs), such as zeolites, aluminophosphates (AlPOs) and metal organic frameworks (MOFs). Initially, a general formation process for CNFMs is described and the 'tool kit' (including synchrotron and non-synchrotron-based techniques) used to examine this complex process is presented. The need for realistic in situ conditions and the balance between this, data quality and time resolution, are also discussed with reference to commonly utilized in situ synchrotron-based experimental cells. The experimental studies into the formation of several CNFM systems are then examined and the role of the synchrotron-based experiments, in context with those obtained from other techniques, is discussed. From this the importance of the synchrotron-based technique is demonstrated, however it is also shown that, to obtain a more complete understanding of the formation process, complementary independent measurements are still often required. During these discussions some of the most common experimental techniques and analytical methods are also discussed in detail and critically assessed.

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

“…As with previous measurements performed on aluminophosphate gels, the SAXS intensity I(q) closely follows a power-law decay k -n with n close to -3 and is indicative of particles present being poorly/irregularly structured (i.e., not compact with sharp interfaces). 25,27 After removing the leading q -3 decay of the I(q) 3 q 3 dependence, it is possible to observe a difference between the scattering profiles. The plots exhibit a broad maximum (defined as q max ), which can be fitted with Gaussian function(s) and approximated to the inverse of the typical size of possible gel aggregates/precursors that form during ZnAPO-34 crystallization.…”

“…35 The formation process has been studied using a unique bespoke setup in which the X-ray-based techniques XAFS, small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS) have been combined with Raman spectroscopy to obtain a more detailed insight into the formation of the Zn 2þ substituted form of the CHA framework. 16,22,25,36 Importantly, this combination of techniques allows us to examine the interplay between the Zn 2þ species, the template molecule, the initial gel species, and the final crystalline material providing for more detailed insight into the essential steps leading to microporous aluminophosphate formation. In addition, these studies and the conclusions drawn from them were also supplemented by both pre-and postsynthesis analysis of the material.…”

Probing zeolites by vibrational spectroscopies

“…The full investigation of complex systems, such as zeolites under working conditions, requires the combined use of different vibrational (IR and Raman), structural (XRD, PDF, SAXS, and EXAFS), electronic (UV-Vis, UPS, XPS, XANES, and XES) and magnetic (NMR and EPR) characterization techniques, 162,364,378,383,494,544,545,737,[934][935][936][937][938][939][940][941][942][943][944][945][946][947][948][949][950] possibly supported by DFT calculations. 22,46,202,364,536,537,553,673,736,863,949,[951][952][953][954][955] Combining information from different experimental techniques is the only way to avoid the intrinsic limitations that each technique possesses such as (ia) the inability of XRD to analyze amorphous phases; (ib) the inability of EPR to detect diamagnetic species; (ic) the inability of NMR to detect nuclei with zero spin; (id) the inability of XRD, PDF, and SAXS to discriminate between different possible oxidation states; (ie) the inability of standard XRD, PDF, SAXS, IR, and Raman to be element-specific; (iia) the difficulty of XRD, PDF, SAXS, and EXA...…”

Particle shape effects in colloidal crystals and colloidal liquid crystals: Small-angle X-ray scattering studies with microradian resolution

“…Structures on the mesoscales, ranging from about a nanometre to a micron, play a key role in a broad range of research fields such as soft matter [1,2], heterogeneous catalysis [3] and biology [4,5]. They can be studied either in direct-space using microscopy or in reciprocal-space using scattering that are complementary to each other.…”