Abstract
The employment of nuclear magnetic resonance (NMR) spectroscopy for studying crystalline porous materials formation is reviewed in the context of the development of in situ methodologies for the observation of the real synthesis medium, with the aim of unraveling the nucleation and growth processes mechanism. Both liquid and solid state NMR techniques are considered to probe the local environment at molecular level of the precursor species either soluble in the liquid phase or present in the reactive gel. Because the mass transport between the liquid and solid components of the heterogeneous system plays a key role in the synthesis course, the two methods provide unique insights and are complementary. Recent technological advances for hydrothermal conditions NMR are detailed and their applications to zeolite and related materials crystallization are illustrated. Achievements in the field are exemplified with some representative studies of relevance to zeolites, aluminophosphate zeotypes, and metal-organic frameworks.
Highlights
Crystalline microporous solids historically include zeolites and zeotype materials mostly metallophosphates, and recently hybrid organic-inorganic coordination polymers called metal organic frameworks (MOFs), has joined this family of compounds [1]
Solvent and host molecules are often found entrapped within their cages and channels interacting strongly with the framework and are suspected to play key role to ensure the structural cohesion [9,10]. They can be removed through postsynthesis procedures, the extra-framework species are usually present in as-made materials
nuclear magnetic resonance (NMR) has been frequently used in microporous formation studies, since it gives the possibilities of gaining detailed information about speciation in both solid and solution phases [18,44]
Summary
Crystalline microporous solids historically include zeolites and zeotype materials mostly metallophosphates, and recently hybrid organic-inorganic coordination polymers called metal organic frameworks (MOFs), has joined this family of compounds [1]. Combination of various techniques to explore wide temporal and spatial domain scales is a required approach to refine as much as possible the current crystallization models of the different synthesis systems To verify such postulated mechanisms, kinetic investigation of the crystallization process represents one of the most effective experimental approaches [29,30,31]. NMR has been frequently used in microporous formation studies, since it gives the possibilities of gaining detailed information about speciation in both solid and solution phases [18,44] This technique provides structural and dynamic insights with distinct spatial and temporal resolution. I will survey the recent technological and methodological developments in the field of in situ NMR of hydrothermal synthesis medium together with past results Within this context, I will expose an overview of main achievements in mechanistic studies of microporous materials. MOFs. representative examples of zeolites, aluminophosphates, and aluminum crystallization carboxylate type MOFs
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