13 research outputs found
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 vast variety of crystalline MOFs have
been identified as being 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 (Tm
< Td). Experimental evidence shows that the Tm of ZIF-8 obtained by
IL infiltration is around 381 °C, and that the glass forming ability
(Tg/Tm) of such melts is above 0.9, i.e. higher than those previously
reported for other meltable MOFs. 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.</div
In situ synchrotronâbased Xâray powder diffraction and microâRaman study of biomass and residue model compounds at hydrothermal conditions
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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
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Mapping Short-Range Order at the Nanoscale in MetalâOrganic Framework and Inorganic Glass Composites
Characterization of nanoscale changes in the atomic structure of amorphous materials is a profound challenge. Established X-ray and neutron total scattering methods typically provide sufficient signal quality only over macroscopic volumes. Pair distribution function analysis using electron scattering (ePDF) in the scanning transmission electron microscope (STEM) has emerged as a method of probing nanovolumes of these materials, but inorganic glasses as well as metalâorganic frameworks (MOFs) and many other materials containing organic components are characteristically prone to irreversible changes after limited electron beam exposures. This beam sensitivity requires âlow-doseâ data acquisition to probe inorganic glasses, amorphous and glassy MOFs, and MOF composites. Here, we use STEM-ePDF applied at low electron fluences (10 e-/Ă
2) combined with unsupervised machine learning methods to map changes in the short-range order with ca. 5 nm spatial resolution in a composite material consisting of a zeolitic imidazolate framework glass agZIF-62 and a 0.67([Na2O]0.9[P2O5])-0.33([AlO3/2][AlF3]1.5) inorganic glass. STEM-ePDF enables separation of MOF and inorganic glass domains from atomic structure differences alone, showing abrupt changes in atomic structure at interfaces with interatomic correlation distances seen in X-ray PDF preserved at the nanoscale. These findings underline that the average bulk amorphous structure is retained at the nanoscale in the growing family of MOF glasses and composites, a previously untested assumption in PDF analyses crucial for future non-crystalline nanostructure engineering
Mapping short-range order at the nanoscale in metalâorganic framework and inorganic glass composites
Metal-organic framework and inorganic glass composites
Metal-organic framework (MOF) glasses have become a subject of study due to their novelty as an entirely new category of melt quenched glass and their 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 optically transparent materials, composed of both MOF and inorganic glass domains. Here, we present the design rules for this family of materials, 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.</p