Vibrational disorder and densification-induced homogenization of local elasticity in silicate glasses

We report the effect of structural compaction on the statistics of elastic disorder in a silicate glass, using heterogeneous elasticity theory with the coherent potential approximation (HET-CPA) and a log-normal distribution of the spatial fluctuations of the shear modulus. The object of our study, a soda lime magnesia silicate glass, is compacted by hot-compression up to 2 GPa (corresponding to a permanent densification of ~ 5%). Using THz vibrational spectroscopic data and bulk mechanical properties as inputs, HET-CPA evaluates the degree of disorder in terms of the length-scale of elastic fluctuations and the non-affine part of the shear modulus. Permanent densification decreases the extent of non-affine elasticity, resulting in a more homogeneous distribution of strain energy, while also decreasing the correlation length of elastic heterogeneity. Complementary (29)Si magic angle spinning NMR spectroscopic data provide a short-range rationale for the effect of compression on glass structure in terms of a narrowing of the Si–O–Si bond-angle and the Si–Si distance

Ionic liquid facilitated melting of the metal-organic framework ZIF-8.

Hybrid glasses from melt-quenched metal-organic frameworks (MOFs) have been emerging as a new class of materials, which combine the functional properties of crystalline MOFs with the processability of glasses. However, only a handful of the crystalline MOFs are meltable. Porosity and metal-linker interaction strength have both been identified as crucial parameters in the trade-off between thermal decomposition of the organic linker and, more desirably, melting. For example, the inability of the prototypical zeolitic imidazolate framework (ZIF) ZIF-8 to melt, is ascribed to the instability of the organic linker upon dissociation from the metal center. Here, we demonstrate that the incorporation of an ionic liquid (IL) into the porous interior of ZIF-8 provides a means to reduce its melting temperature to below its thermal decomposition temperature. Our structural studies show that the prevention of decomposition, and successful melting, is due to the IL interactions stabilizing the rapidly dissociating ZIF-8 linkers upon heating. This understanding may act as a general guide for extending the range of meltable MOF materials and, hence, the chemical and structural variety of MOF-derived glasses

Sodium Ion Conductivity in Superionic IL-Impregnated Metal-Organic Frameworks: Enhancing Stability Through Structural Disorder

Abstract: Metal-organic frameworks (MOFs) are intriguing host materials in composite electrolytes due to their ability for tailoring host-guest interactions by chemical tuning of the MOF backbone. Here, we introduce particularly high sodium ion conductivity into the zeolitic imidazolate framework ZIF-8 by impregnation with the sodium-salt-containing ionic liquid (IL) (Na0.1EMIM0.9)TFSI. We demonstrate an ionic conductivity exceeding 2 × 10−4 S · cm−1 at room temperature, with an activation energy as low as 0.26 eV, i.e., the highest reported performance for room temperature Na+-related ion conduction in MOF-based composite electrolytes to date. Partial amorphization of the ZIF-backbone by ball-milling results in significant enhancement of the composite stability towards exposure to ambient conditions, up to 20 days. While the introduction of network disorder decelerates IL exudation and interactions with ambient contaminants, the ion conductivity is only marginally affected, decreasing with decreasing crystallinity but still maintaining superionic behavior. This highlights the general importance of 3D networks of interconnected pores for efficient ion conduction in MOF/IL blends, whereas pore symmetry is a less stringent condition

Metal-organic framework and inorganic glass composites

Abstract: Metal-organic framework (MOF) glasses have become a subject of interest as a distinct category of melt quenched glass, and have potential applications in areas such as ion transport and sensing. In this paper we show how MOF glasses can be combined with inorganic glasses in order to fabricate a new family of materials composed of both MOF and inorganic glass domains. We use an array of experimental techniques to propose the bonding between inorganic and MOF domains, and show that the composites produced are more mechanically pliant than the inorganic glass itself

Nanoindentation Study of the Surface of Ion-Exchanged Lithium Silicate Glass

Variations in mechanical properties (stiffness and hardness) were measured as a function of case depth in ion-exchange glasses using nanoindentation. A simple silicate composition, 30Li₂O–70Si₂O, was exchanged (Li⁺ ↔ K⁺) at several different temperatures, below and above the glass transition, to evaluate the effect of exchange temperature on mechanical properties throughout the ion-exchange layer. Significant enhancements in Young’s modulus and hardness were found near the edge in ion-exchanged glasses and attributed to compressive stress and the mixed-alkali effect. Indent size effect-like behaviors were observed in the untreated and ion-exchange samples alike near the sample edge; this was explained by surface-condition sensitivity and compressive stress found within this region. The elastic recovery and resistance to plastic deformation were calculated to assess the effect of ion exchange on elastic and plastic mechanical responses. Microhardness measurements of the exchanged samples were also made for comparison

Research data supporting The Reactivity of an Inorganic Glass Melt with ZIF-8

This dataset contains all experimental results published in the work: The Reactivity of an Inorganic Glass Melt with ZIF-8, L. Longley et al., Dalton Trans., (2021), DOI: 10.1039/d1dt00152c This work explores the thermal behaviour of ZIF-8, Zn(meIm)2, in the presence of a sodium fluoroaluminophosphate glass melt. This system was probed through differential scanning calorimetry and thermogravimetric analysis. The structural integrity of ZIF-8 was then determined by a combination of powder X-ray diffraction, Fourier transform infra-red and 1H nuclear magnetic resonance spectroscopy. Scanning electron microscopy and image analysis were used to quantify the particle size distribution of the synthesised ZIF-8 framework. Due to the large variety of data types contained within this dataset individual read-me files detail necessary information for each separate data type

The reactivity of an inorganic glass melt with ZIF-8.

The thermal behaviour of ZIF-8, Zn(meIm)2 in the presence of a sodium fluoroaluminophosphate glass melt was probed through differential scanning calorimetry and thermogravimetric analysis. The structural integrity of ZIF-8 was then determined by a combination of powder X-ray diffraction, Fourier transform infra-red and 1H nuclear magnetic resonance spectroscopy

Sodium Ion Conductivity in Superionic IL-Impregnated Metal-Organic Frameworks: Enhancing Stability Through Structural Disorder

Metal—organic frameworks (MOFs) are intriguing host materials in composite electrolytes due to their ability for tailoring host-guest interactions by chemical tuning of the MOF backbone. Here, we introduce particularly high sodium ion conductivity into the zeolitic imidazolate framework ZIF-8 by impregnation with the sodium-salt-containing ionic liquid (IL) (Na0.1¬EMIM0.9)TFSI. We demonstrate an ionic conductivity exceeding 2×10-4 S ⋅cm-1 at room temperature, with an activation energy as low as 0.26 eV, i.e., the highest reported performance for room temperature Na+-related ion conduction in MOF-based composite electrolytes to date. Partial amorphization of the ZIF-backbone by ball-milling results in significant enhancement of the composite stability, reflecting in persistent and stable ionic conductivity during exposure to ambient air over up to 20 days. While the introduction of network disorder decelerates IL exudation and interactions with ambient contaminants, the ion conductivity is only marginally affected, decreasing linearly with decreasing crystallinity but still maintaining superionic behavior. This highlights the general importance of 3D networks of interconnected pores for efficient ion conduction in MOF/IL blends, whereas pore symmetry is a presumably less stringent condition.</p

Research data supporting Metal-Organic Framework and Inorganic Glass Composites

This data set contains all of the data presented in the paper "'Metal-Organic Framework and Inorganic Glass Composites', L. Longley et. al, Nature Comms, Accepted”. This consists of structure and property data characterising a new class of hybrid glass – inorganic glass composites composed of glassy ZIF-62, [Zn(Im)1.75(bIm)0.25] (Im = C3H3N2− and bIm = C7H5N2−) and a series of aluminophosphate glasses of general formula (1−x)([Na2O]z[P2O5])-x([AlO3/2][AlF3]y). The structure of these composites is determined via powder X-ray diffraction (PXRD), energy dispersive X-ray spectroscopy (EDX), attenuated total reflectance infra-red spectroscopy (ATR-IR), Raman spectroscopy, scanning electron microscopy (SEM), light microscopy, 1H and 31P nuclear magnetic resonance (NMR), density measurements and X-ray total-scattering. The thermal properties during composite formation where characterised by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The mechanical properties and ionic conductivity of the composites were investigated via nano-indentation and impedance spectroscopy respectively. Each sub folder contains README files for each data collection technique explaining its contents and the methodology by which the data was gathered