The Development of Hybrid Liquids and Gases

Lead Research Organisation: University of Cambridge
Department Name: Materials Science & Metallurgy

Abstract

Metal-organic frameworks (MOFs) are a class of porous materials with specific surface areas comparable to or greater than materials such as activated carbons and zeolites. Their high surface areas combined with the variety of functional groups that can be accommodated into the organic backbone of the structures compared to zeolites has led to research into the use of MOFs in as storage and separations, catalysis and radioactive waste recycling.
Although MOF research has previously been focused on synthesis and characterisation of crystalline frameworks, recent research has found a subset of MOFs that are capable of melting and in which the inorganic-organic connectivity of the structure is retained in the liquid phase. Cooling of these liquids results in the formation of hybrid organic-inorganic glasses which form a new class of materials distinct from i) inorganic, (ii) metallic and (iii) organic categories known to date.
The aim of the PhD project is to further examine the basic science of this new class of materials through examining the generality of glass formation in the 55,000 known MOF structures. The crystalline MOFs will be synthesised using established solvothermal, ball milling or steam assisted methodologies and X-ray powder diffraction and differential scanning calorimetric techniques used to characterise their glass forming nature. Investigations of the liquid and glass phases will be performed using pair distribution function analysis and X-ray absorption fine structure techniques. Characterisation of the glass species formed will also be conducted by techniques such as nano-indentation with an aim of investigating the potential applications of hybrid glasses.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509620/1 01/10/2016 30/09/2021
1937211 Studentship EP/N509620/1 01/10/2017 30/09/2021 Louis Longley
 
Description Metal-organic frameworks (MOFs) are a class of materials created by joining inorganic nodes with organic linkers into a three-dimensional framework. These frameworks are typically highly porous and the wide variety of different nodes and linkers means that they exhibit a wide variety of structures, with over 70, 000 structures reported in the Cambridge Structural Database.

The majority of MOFs reported have been crystalline in nature, meaning they have a repeating long range structure, however amorphous MOFs, MOFs lacking a long range repeating structure, can be produced through a variety of thermo-mechanical and synthetic routes. In 2014 a crystalline MOF framework was found to form a liquid on heating, which when cooled back to room temperature resulted in the formation of an amorphous material. As this material is formed from a liquid state it is an example of a glass, which is a liquid which has been 'trapped' into a low temperature solid state, avoiding formation of a crystalline phase. Glass MOFs represent a new family of glass materials, due to their combination of inorganic and organic elements, which makes them distinct from inorganic, polymer (purely organic), and metallic glasses. Only a small subset of existing MOF crystals have an accessible liquid state however, with the majority of frameworks shown to decompose before melting upon heating.

A key focus on my work has been on creating and characterising MOF glasses formed from more than one constituent MOF component. So far two distinct types of such glasses have been identified; 'blends' in which both components are MOFs which can melt and form glasses separately, and 'fluxes' in which the liquid state of one MOF is used to drive melting in a different crystalline framework which does not have an accessible liquid state when heated on its own. My work focused on the synthesis of these materials and there characterisation using X-ray total scattering and pair-distribution functions, a technique which probes the atom-atom correlations present in structures.
In addition to this I have also contributed PDF analysis to work on porous MOF glasses, and to research into the structural development of MOF glasses during treatment at elevated temperatures for extended periods of time.
Exploitation Route MOF glasses represent a new class of materials, occupying a region intermediate between inorganic glasses and polymer glasses in terms of structure, and mechanical properties. New classes of materials occupying new regions of materials space will have properties and applications that are unique. The chemical versatility of MOF glasses, which they share with their parent crystals, combined with the processing potential of the liquid state means that they could have a variety of applications, however many basic structural questions still need to be answered. My work has contributed to elucidating the structure of a variety of MOF glasses and on investigating ways in which the chemical functionality of the glass phase can be expanded. This is work necessary before more application focused research in either industry or academia can occur.
Sectors Chemicals,Energy

 
Description Collaboration with Otto Schott Institute for Materials Research 
Organisation Friedrich Schiller University Jena (FSU)
Country Germany 
Sector Academic/University 
PI Contribution Produced and characterised samples via a variety of techniques.
Collaborator Contribution Produced and characterised samples, specifically produced Inorganic glasses and characterised experimental samples through confocal microscopy, Raman spectroscopy, Nano-indentation and solid state NMR.
Impact This output has resulted in the publication of the following paper: Shichun Li et al., "Mechanical Properties and Processing Techniques of Bulk Metal-Organic Framework Glasses," J. Am. Chem. Soc., vol. 141, no. 2, pp. 1027-1034, 2019.
Start Year 2018
 
Description Collaboration with the Diamond Light Source - i15-1 beamline 
Organisation Diamond Light Source
Country United Kingdom 
Sector Private 
PI Contribution I produced samples and collaborated with data analysis and interpretation.
Collaborator Contribution Prof. Dave Keen, Dr Dean Keeble, and Dr Philip Chater provided training and expertise in collecting and analysing X-ray total scattering data.
Impact The following papers contain data resulting from this collaboration: L. Longley et al., "Flux melting of metal-organic frameworks," Chem. Sci., vol. 10, no. 12, pp. 3592-3601, 2019 J. Zhang et al., "Structural evolution in a melt-quenched zeolitic imidazolate framework glass during heat-treatment," Chem. Commun., vol. 55, no. 17, pp. 2521-2524, 2019. L. Longley et al., "Liquid phase blending of metal-organic frameworks," Nat. Commun., vol. 9, no. 1, pp. 2-11, 2018. C. Zhou et al., "Metal-organic framework glasses with permanent accessible porosity," Nat. Commun., vol. 9, no. 1, pp. 1-9, 2018. C. Zhou et al., "Thermodynamic features and enthalpy relaxation in a metal-organic framework glass," Phys. Chem. Chem. Phys., vol. 20, no. 27, pp. 18291-18296, 2018
Start Year 2017
 
Description Collaboration with the Diamond Light Source - i20 beamline 
Organisation Diamond Light Source
Country United Kingdom 
Sector Private 
PI Contribution Provided samples, conducted data collection and analysis.
Collaborator Contribution Provided training in EXAFS and XANES data analysis and collection.
Impact Work still ongoing - no concrete outputs yet.
Start Year 2019
 
Description Collaboration with the Electron Microscopy Group - Transmission Electron Microscopy of MOF-glasses 
Organisation University of Cambridge
Department Department of Materials Science & Metallurgy
Country United Kingdom 
Sector Academic/University 
PI Contribution I synthesised the samples and on which they conducted their characterisation, as well as using many other characterisation techniques myself.
Collaborator Contribution They examined samples provided using Transmission Electron Microscopy and analysed the resulting data.
Impact The following papers contain results which come from this collaboration: L. Longley et al., "Flux melting of metal-organic frameworks," Chem. Sci., vol. 10, no. 12, pp. 3592-3601, 2019. S. M. Collins et al., "Phase diagrams of liquid-phase mixing in multi-component metal-organic framework glasses constructed by quantitative elemental nano-tomography," APL Mater., vol. 7, no. 9, pp. 0-8, 2019. L. Longley et al., "Liquid phase blending of metal-organic frameworks," Nat. Commun., vol. 9, no. 1, pp. 2-11, 2018.
Start Year 2017
 
Description Collaboration with the Nitschke Group - DSC on coordination cages 
Organisation University of Cambridge
Department Department of Chemistry
Country United Kingdom 
Sector Academic/University 
PI Contribution I provided training and support in the use and interpretation of Differential Scanning Calorimetry.
Collaborator Contribution They synthesised the samples and conducted many other experimental techniques to understand there properties and structure.
Impact This collaboration resulted in a paper, L. Ma et al., "Coordination cages as permanently porous ionic liquids," Nat. Chem., pp. 1-4, Feb. 2020.
Start Year 2019
 
Description Collaboration with the State Key Laboratory of Silicate Materials for Architectures - Wuhan University of Technology 
Organisation Wuhan University of Technology
Country China 
Sector Academic/University 
PI Contribution I prepared samples, and collaborated with them on the interpretation of the results they generated.
Collaborator Contribution They conducted scanning differential calorimetry on samples sent to them.
Impact The following papers are a result of this collaboration: 1. C. Zhou et al., "Thermodynamic features and enthalpy relaxation in a metal-organic framework glass," Phys. Chem. Chem. Phys., vol. 20, no. 27, pp. 18291-18296, 2018. 2. C. Zhou et al., "Metal-organic framework glasses with permanent accessible porosity," Nat. Commun., vol. 9, no. 1, pp. 1-9, 2018. 3. L. Longley et al., "Liquid phase blending of metal-organic frameworks," Nat. Commun., vol. 9, no. 1, pp. 2-11, 2018. 4. J. Zhang et al., "Structural evolution in a melt-quenched zeolitic imidazolate framework glass during heat-treatment," Chem. Commun., vol. 55, no. 17, pp. 2521-2524, 2019. 5. L. Longley et al., "Flux melting of metal-organic frameworks," Chem. Sci., vol. 10, no. 12, pp. 3592-3601, 2019.
Start Year 2017