Optical Spectroscopy and Microscopy Studies on the Spatial Distribution and Reaction Dynamics in Zeolites

Abstract

This Perspective describes current research into the photochemistry of zeolites, pointing out issues yet to be resolved and suggesting future directions of investigation. The fascinating host materials are known to act as a support for guest ions, molecules, or clusters both within their large interior cage/channel networks and on their exterior surfaces, together providing rich chemistry. Two techniques have proven particularly successful for their study, diffuse reflectance transient absorption spectroscopy and optical microscopy. The various properties revealed by these techniques include intracrystalline and intercrystalline migration, migration-assisted photochemical reactions, and heterogeneous distribution of guest molecules among and within crystals.

Supramolecular Organization in Confined Nanospaces

“…This example evidences the delicate interplay of host‐guest interactions in hydrophilic zeolites: fine differences in the framework structure, or in the nature of the charge balancing cations, may affect significantly the stability and dynamic behavior of the confined supramolecular assembly. These factors also govern the organization of more complex guests such as lanthanides, metal complexes,, or dyes, inside hydrophilic hosts …”

“…These factors also govern the organization of more complex guests such as lanthanides, [51] metal complexes, [561,562] or dyes, inside hydrophilic hosts. [563][564][565][566]…”

Transient absorption spectroscopy and photochemical reactivity of CAU-8

“…[10][11][12] Zeolites and mesoporous aluminosilicates have been among the preferred hosts to perform heterogeneous photochemical reactions, with the aim being to achieve a product selectivity higher than in the liquid phase. 4,[12][13][14][15] In this context, a more recent class of crystalline porous materials that have considerable possibilities in photochemistry are Metal Organic Frameworks (MOFs). [16][17][18][19][20][21] These solids are constituted by metal ions or clusters of metal ions at nodal positions held in place by rigid bi-or multipodal organic linkers, with aromatic polycarboxylates being the most widely used linkers.…”

Determination of the depth profile distribution of guest species in microporous materials using the voltammetry of immobilized particles methodology: application to lapachol attachment to palygorskite and kaolinite

“…7 On the other hand, the distribution of pharmacologically active guests in nanostructured materials is relevant for determining the kinetics and performance of drug delivery processes. [8][9][10] As recently studied [11][12][13] and reviewed 14 by Hashimoto, methods reported for this purpose include diffuse reflectance transient absorption spectroscopy, 14 photoinduced electron transfer and charge separation, [15][16][17][18][19][20][21][22] confocal optical microscopy, 23 microscope FTIR mapping, 24 and multidimensional NMR correlation spectroscopy, 25 among others. 14 The influence of charge compensating ions to control the distribution and conformation of the guest species within the channels of ion-permeable microporous materials should be noted, 7,14 and also that species distribution can influence photochemical 26,27 and mechanical 28 properties of these kinds of materials.…”