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The Different Organization of Water in Zeolite L and Its MOF Mimic

preprint
submitted on 22.02.2019 and posted on 25.02.2019 by gloria tabacchi, Ettore Fois
Abstract:
Confinement of molecules inside one dimensional arrays of channel-shaped cavities has led to an impressive number of technologically interesting materials. However, the interactions governing the properties of the supramolecular aggregates still remain obscure, even in the case of the most common guest molecule: water. Herein, we use computational chemistry methods (#compchem) to study the water organization inside two different channel-type environments: zeolite L – a widely used matrix for inclusion of dye molecules, and ZLMOF – the closest metal-organic-framework mimic of zeolite L. In ZLMOF, the methyl groups of the ligands protrude inside the channels, creating nearly isolated nanocavities. These cavities host well-separated ring-shaped clusters of water molecules, dominated mainly by water-water hydrogen bonds. ZLMOF channels thus provide arrays of „isolated supramolecule“ environments, which might be exploited for the individual confinement of small species with interesting optical or catalytic properties. In contrast, the one dimensional nanochannels of zeolite L contain a continuous supramolecular structure, governed by the water interactions with potassium cations and by water-water hydrogen bonds. Water molecules impart a significant energetic stabilization to both materials, which increases by increasing the water content in ZLMOF, while the opposite trend is observed in zeolite L. The water network in zeolite L contains an intriguing hyper-coordinated structure, where a water molecule is surrounded by 5 strong hydrogen bonds. Such a structure, here described for the first time in zeolites, can be considered as a water pre-dissociation complex and might explain the experimentally detected high proton activity in zeolite L nanochannels.

Funding

This work was supported by the Italian MIUR, within the frame of the following projects: PRIN2015 “ZAPPING” (2015HK93L7), ImPACT (FIRB RBFR12CLQD), and University of Insubria Far 2016-2017.

History

Email Address of Submitting Author

gloria.tabacchi@uninsubria.it

Institution

University of Insubria

Country

Italy

ORCID For Submitting Author

0000-0002-1988-6775

Declaration of Conflict of Interest

No conflict of interest

Version Notes

1st version

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