Unravelling the High-Pressure Behaviour of Dye-Zeolite L Hybrid Materials

Abstract

Self-assembly of chromophores nanoconfined in porous materials such as zeolite L has led to technologically relevant host-guest systems exploited in solar energy harvesting, photonics, nanodiagnostics and information technology. The response of these hybrid materials to compression, which would be crucial to enhance their application range, has never been explored to date. By a joint high-pressure in situ synchrotron X-ray powder diffraction and ab initio molecular dynamics approach, herein we unravel the high-pressure behaviour of hybrid composites of zeolite L with fluorenone dye. High-pressure experiments were performed up to 6 GPa using non-penetrating pressure transmitting media to study the effect of dye loading on the structural properties of the materials under compression. Computational modelling provided molecular-level insight on the response to compression of the confined dye assemblies, evidencing a pressure-induced strengthening of the interaction between the fluorenone carbonyl group and zeolite L potassium cations. Our results reveal an impressive stability of the fluorenone-zeolite L composites at GPa pressures. The remarkable resilience of the supramolecular organization of dye molecules hyperconfined in zeolite L channels may open the way to the realization of optical devices able to maintain their functionality under extreme conditions.

Supramolecular Organization in Confined Nanospaces

“…Though the composites are technically suitable for use in solar cells and sensing applications (Section 7), acidity inside the zeolite L channel is still a limiting factor towards attaining maximum concentration of donor molecules inside the host . Nevertheless, these composites have proven to be thermally robust, and mechanically resilient up to GPa pressures; in addition, the host matrix is easy to synthesize in form of disc‐shaped crystals, for which a uniform filling of dye molecules along the channels can be accomplished . Also, the use of nanosized zeolite L crystals could further improve the luminescence properties of these hybrid materials, disclosing potential medical applications as theranostic agents …”

“…Nonetheless, the atomistic structure of these versatile compounds often remains unexplored, as suggested by the scarce number of diffraction studies on dye‐zeolite hybrids ,. Fortunately, computational modeling comes to the rescue .…”

“…When the concentration of the dye increases up to a close‐packing regime (Figure ), this interaction still remains important, and drives the formation of a peculiar space‐filling arrangement of chromophore molecules . Under compression, this fluorenone‐nanoladder, protected by the zeolite host, withstands GPa pressures and responds by approaching with the carbonyl groups the K + cations, i. e., by strengthening the main stabilizing interaction . Such impressive resilience to high pressure is a promising step for extending the application range of dye‐zeolite materials beyond normal conditions.…”

Compressibility behavior and pressure-induced over-hydration of zeolite K AlSi-L

“…Since the analysis of the observed diffraction patters did not show any phase transition, all the structural refinements were carried out in the original K-L space group P6/mmm, starting from the atomic coordinates reported by Gigli et al [16] and using the GSAS package [28] with EXPGUI interface [29]. To allow the comparison with previous literature data on K-gallosilicate with LTL topology, the atom labels were after Lee et al [23].…”

“…Notwithstanding, several studies have dealt with the incorporation of dyes into zeolites [10][11][12][13][14][15], only a work [16] until now exploited the behavior of these systems under high pressure trying to establish whether compression could favor a different distribution of the dye molecules and lead to an improvement of the optical properties of the materials under investigation. Very recently, Gigli et al [16] studied the high-pressure behavior of some hybrid composites formed by zeolite L and fluorenone dye, through an integrated experimental-computational approach. The hybrid system resulted to be very stable upon pressure, undergoing only a modest variation of the pore volumes, thus affecting only to a minor extent the molecular structure of the organic guests.…”