The fellowship entitled “Understanding and Engineering Phonon Properties for Controlling Mechanical and Thermal Characteristics in Metal-Organic Frameworks” will finance his further PhD studies. Thomas will continue his work along the following lines.
Metal-organic frameworks (MOFs) are an emerging class of materials often showing surprising properties like negative thermal expansion and negative Poisson’s ratios. The porous frameworks consisting of heavy metal centers connected by organic linkers often have internal surface areas of several thousand square meters per gram. Besides more traditional applications of MOFs (gas adsorption and separation, catalysis) exploiting the huge amounts of internal surface area, a more recent trend is to integrate MOFs into functional devices. However, design of that kind requires an in-depth understanding of the fundamental relations between the structure of a MOF and its mechanical, electrical, thermal, etc. characteristics. Therefore, the aim of the project will be to shed light on the mechanical and thermal properties, which can be conveniently described within the phonon picture of crystalline matter. Beyond that, a combined approach of theoretical and experimental techniques will be applied to study also anharmonic effects such as the thermal expansion coefficients as a function of structural components.
As part of Materials Chemistry Frontiers’ themed collection "In honour of Professor Robert H. Grubbs for his 50-year contributions in metathesis" a review article on the chemistry and technology of poly(dicyclopentadiene) (pDCPD) and pDCPD based materials was disclosed as open access article.
During the last two decades, pDCPD prepared by Ring-opening Metathesis Polymerization emerged as an important competitor for epoxy- and polyester resins. An important fundament for this development, going far beyond established pDCPD industries, is certainly the introduction of functional-group tolerant olefin metathesis catalysts by Prof. Grubbs. Accordingly, the article starts with discussing the need for latent, functional group tolerant and air insensitive initiators and describes the progress in this field. In the next section the progress in polymer chemistry and physics of pDCPD is presented, covering in particular the fields of durability, copolymers, nanocomposites, fiber reinforced pDCPD and the use of dicyclopentadiene based formulations in self-healing applications. Furthermore, emerging processing techniques such as frontal polymerization and additive manufacturing are highlighted. Macro- as well as microporous pDCPD based materials are presented according to their type of preparation. A short chapter on polymers from functionalized dicyclopentadiene followed by a personal view on challenges and perspectives elaborating the frontiers of the current research in the field close the article.
In an interdisciplinary work carried out within Graz University of Technology, a biocatalytic system based on the zeolitic imidazolate framework-8 (ZIF-8) is introduced. The catalytic sytems is obtained in a one-pot process by directly combining the enzyme horseradish peroxidase (HRP), iron oxide magnetic nanoparticles, the ligand and metal ions, in water at room temperature. The resulting system provides a useful platform for the next generation of reusable/repositionable biocatalysts.
The Slugovc group reported on completely solvent and catalyst free aza‐Michael addition reactions of azoles to liquid Michael acceptors in EurJOC. As long as the solubility of the azole in the reaction mixture is sufficient, the addition reaction proceeds towards completion in several hours at 80 °C and no solvents are needed during work-up. Thus, the disclosed protocol is on the one hand as resource saving as possible and on the other hand the importance of using high concentration conditions for (aza-)Michael addition reactions is illustrated. The obtained products will be used in the construction of porous coordination polymers.
Phonons crucially impact a variety of properties of organic semiconductor materials. For instance, charge- and heat transport depend on low-frequency phonons, while for other properties, such as the free energy, especially high-frequency phonons count. For all these quantities one needs to know the entire phonon band structure, whose simulation becomes exceedingly expensive for more complex systems when using methods like dispersion-corrected density functional theory (DFT). Therefore, in the present contribution researchers from Leoben, Bochum and Graz evaluate the performance of more approximate methodologies, including density functional tight binding (DFTB) and a pool of force fields (FF) of varying complexity and sophistication. Beyond merely comparing phonon band structures, they also critically evaluate to what extent derived quantities, like temperature-dependent heat capacities, mean squared thermal displacements, and temperature-dependent free energies are impacted by shortcomings in the description of the phonon bands.
Zeolitic imidazolate framework (ZIF) biocomposites show the capacity to protect and deliver biotherapeutics. To date, the progress in this research area is based on laboratory batch methods. Now, the first continuous flow synthetic method is presented for the encapsulation of a model protein (bovine serum albumin, BSA) and a clinical therapeutic (α1‐antitrypsin, AAT) in ZIF‐8. In a collaborative work, the in situ kinetics of nucleation, growth, and crystallization of BSA@ZIF‐8 were studied by small‐angle X‐ray scattering. By controlling the injection time of ethanol, the particle growth could be quenched by ethanol‐induced crystallization from amorphous particles to ZIF‐8 crystals. The particle size of the biocomposite was tuned in the 40–100 nm range by varying residence time prior to introduction of ethanol. As a proof‐of‐concept, this procedure was used for the encapsulation of AAT in ZIF‐8. Upon release of the biotherapeutic from the composite, the trypsin inhibitor function of AAT was preserved.
A team of researchers from Graz, Adelaide, Bologna and Stockholm systematically varied the composition (i.e. relative amounts of ligand (2-methylimidazole), metal precursor (Zn(OAc)2·2H2O), and protein) and post synthetic treatments (i.e. washes with water or water/ethanol) to prepare a series of protein@ZIF biocomposites. These data were used to construct two ternary phase diagrams that showed the synthesis conditions employed gave rise to five different phases including, for the first time, biocomposites based on ZIF-CO3-1.
They examined the influence of the different phases on two properties relevant to drug delivery applications: encapsulation efficiency and release profile. The encapsulation efficiencies of bovine serum albumin and insulin were phase dependent and ranged from 75% to 100%. In addition, release profiles showed that 100% protein release varied between 40 and 300 minutes depending on the phase. This study provides a detailed compositional map for the targeted preparation of ZIF-based biocomposites of specific phases and a tool for the straightforward analysis of the crystalline phases of ZIF based materials (web application named “ZIF phase analysis” available). These data will facilitate the progress of ZIF bio-composites in the fields of biomedicine and biotechnology. Read the work in Chemical Science (Open Access).
In a cooperation of the KU Leuven and Graz University of Technology it was demonstrated, that MAF‐252, a crystalline coordination polymer, is obtained from the solvent‐free reaction of ZnO with 3‐(2‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole. MAF‐252 can be synthesized in powder form and deposited as thin films, starting from ZnO powder and layers, respectively. Chemical vapor deposition (CVD) of MAF‐252 enables conformal and patterned thin films, even on high aspect ratio features.
The Slugovc group in collaboration with Sergey Borisov communicated a hydrocarbon based polymeric material, which rapidly reacts with oxygen. To obtain such an unprecedented material, emulsion templating of norbornadiene and curing with Ring-opening Metathesis Polymerization are used. The resulting cross-linked monolithic foams in unoxidized state exhibit appealing mechanical properties combining high Young’s moduli with pronounced ductility and scavenge 300 mg oxygen/g foam reducing the final oxygen level of a closed volume of air to at least 5 ppmv oxygen in less than a day at room temperature. A combination of the porous morphology and the chemical nature of the polymer is held responsible for the material’s high reactivity with molecular oxygen.
Researchers around Elisabeth Hengge present a method to in situ monitor the adsorption and desorption of self-assembled monolayers on nanoporous gold by resistometry, using cysteine as example and introduce herewith a new technique capable of characterizing the formation of monolayers on porous substrates. During the adsorption an overall relative change in resistance of 18% is detected, which occurs in three distinct stages. First, the cysteine molecules are adsorbed on the outer surface. In the second stage, they are adsorbed on the internal surfaces and in the last stage the reordering accompanied by additional adsorption takes place. The successful binding of cysteine on the Au surface was confirmed by cyclic voltammetry, which showed a significant decrease of the double-layer capacitance.
The Slugovc group described in a recent paper in Macromolecular Chemistry and Physics the effect of enhancing the crosslinking degree in polyHIPEs made from dicyclopentadiene by additionally using a crosslinking comonomer. Foams of 80% porosity with 10–40 wt% comonomer content in the continuous phase are prepared and show similar porosities and morphological characteristics as foams prepared with dicyclopentadiene alone. However, foams containing the crosslinking comonomer recover their initial shape and porosity upon drying of swollen samples. This newly introduced feature enables the use of this porous material in applications, which demand repeated swelling and drying.
Phonon properties of MOFs are largely unexplored, despite their relevance for thermal and electrical conductivities, thermal expansion, and mechanical properties. In the latest research paper of Kamencek, Bedoya-Martínez and Zojer quantum-mechanical simulations are used to provide an in-depth analysis of the phonon properties of isoreticular MOFs. Phonon band structures, spatial confinements of modes, projected densities of states, and group velocity distributions are considered. Additionally, the character of selected modes is discussed based on real-space displacements, and the change of phonon properties of MOFs upon altering constituents (mass and spatial extent, bonding structure, etc.) are addressed. The presented results provide the foundations for an in-depth understanding of the vibrational properties of MOFs and, therefore, pave the way for a future rational design of systems with well-defined phonon properties.
A consortium of researchers from the University of Adelaide, the Australian National University and Graz University of Technology show in their latest JACS paper, that a porous hydrogen-bonded organic framework (HOF) constructed from water-soluble tetra-amidinium and tetracarboxylate building blocks can encapsulate and stabilize biomolecules to elevated temperature, proteolytic and denaturing agents, and extend the operable pH range for catalase activity. The HOF, which readily retains water within its framework structure, can also protect and retain the activity of enzymes such as alcohol oxidase, that are inactive when encapsulated within zeolitic imidazolate framework (ZIF) materials. Such HOF coatings could provide valid alternative materials to ZIFs: they are metal free, possess larger pore apertures, and are stable over a wider, more biologically relevant pH range.
A crucial factor determining charge transport in organic semiconductors is the electronic coupling between the molecular constituents, which is heavily influenced by the relative arrangement of the molecules. Using the example of quinacridone, Egbert Zojer at al. identify in their latest Chem. Mater. paper the combination of Pauli repulsion and orbital rehybridization as the driving force steering the system toward a structure in which the electronic coupling is minimal. This underlines that the design of high-performance materials cannot rely on the “natural” assembly of the π-conjugated backbones of organic semiconductors into their most stable configurations.
Anne-Marie Kelterer works in the field of Computational Chemistry. As an associate researcher of the lead-project she will contribute with her quantum chemical and electronic structure knowledge to the MOF research.
A team of researchers from KU Leuven, Vrije Universiteit Brussel and Porous Materials @ Work disclosed their latest results on growing MOF films from the gas-phase in Chemical Communications. Copper dicarboxylate metal-organic framework films are deposited via chemical vapour deposition. Uniform films with an out-of-plane orientation and accessible porosity are obtained from the reaction of copper and copperoxide with vaporised dicarboxylic acid linkers.
Recent work in biomolecule‐metal–organic framework (MOF) composites has proven to be an effective strategy for the protection of proteins. However, for other biomacromolecules such as nucleic acids, the encapsulation into nano MOFs and the related characterizations are in their infancy. This publication reports the encapsulation of a complete gene‐set in zeolitic imidazolate framework‐8 (ZIF‐8) MOFs and cellular expression of the gene delivered by the nano MOF composites.
Understanding the stability of zeolitic imidazolate framework-8 (ZIF-8) under physiological conditions is critical in biotechnology and biomedicine for biosensing, biocatalysis, and drug delivery. The use of ZIF-8 has shown that this metal organic framework (MOF) and its derived bio-composites can degrade in presence of buffer solutions. Here a team of researchers from Australia, Germany and Graz presents an in-depth analysis of the structural and chemical changes of pure ZIF-8 particles exposed to phosphate buffered saline (PBS) media. Have a read of the article in CrystEngComm.
Motile metal−organic frameworks (MOFs) are potential candidates to serve as small‐scale robotic platforms for applications in environmental remediation, targeted drug delivery, or nanosurgery. Here, magnetic helical microstructures coated with a kind of zinc‐based MOF, zeolitic imidazole framework‐8 (ZIF‐8), with biocompatibility characteristics and pH‐responsive features, are successfully fabricated. Moreover, it is shown that this highly integrated multifunctional device can swim along predesigned tracks under the control of weak rotational magnetic fields. The proposed systems can achieve single‐cell targeting in a cell culture media and a controlled delivery of cargo payloads inside a complex microfluidic channel network. See the article in Advanced Materials.
On June 27th, 2019 a networking meeting on energy materials research at TU Graz took place (8:30 to about 18:00 in the lecture room H “Ulrich Santner” Kopernikusgasse 24).
The event was jointly organized by VARTA Micro Innovation GmbH and the lead-project Porous Materials @ Work and aimed at connecting the expertise of the many groups active in the field. Additionally, representatives of industries were present. The meeting consisted of talks (12+3 min) introducing the research fields, expertise and special equipment of the research groups, a poster session and ample time for networking.
Fully oriented and functional MOF‐on‐MOF films were achieved via epitaxial growth in solution. In a collaborative communication, groups from Japan, Australia and Graz University of Technology exploited the alignment of MOF multi‐layer films on an oriented Cu(OH)2 film. Ag nanoparticles accommodated in aligned pores with anisotropic shape in the selective layer of MOF‐on‐MOF film showed unique anisotropic plasmon resonances.
The Zojer group tested different computational approaches for describing charge‐transport parameters in organic semiconductor crystals using the α‐polymorph of quinacridone as a prototypical example. A rather complex tight‐binding model is fitted to the electronic band structure. Using this model, it is possible to obtain intermolecular electronic couplings and effective masses and to decompose electronic bands into individual contributions. Yet, the gained know-how, published in Advanced Theory and Simulations, will enable to describe charge‐transport in microporous materials such as MOFs and COFs.
A team of Australian and Austrian researchers studied the encapsulation of carbohydrates in metal organic frameworks (MOFs). Carbohydrates, as pure molecules or as a component of proteins and cells, perform essential biological functions. Thus, an understanding of the role of carbohydrates in the formation of MOF-based bio-composites will facilitate their application to biotechnology and medicine. In particular the role of carbohydrate molecular weight and chemical functionalization in the formation of carbohydrate@MOF composites was uncovered in the recent publication in Materials Horizons. The carboxylation of carbohydrates leads to an enhanced concentration of metal cation at the surface of the biomolecule: this triggers the rapid self-assembly of zeolitic-imidazolate framework 8 (ZIF-8) and related polymorphs.
...took place on Feb. 28th, 2019. Organized by Efthymia Vakalopoulou, Tobias Burger and Christian Winkler 12 PhD students presented their progress. The event closed with an inspiring guest lecture of Prof. Shuhei Furukawa from Kyoto University.
Researchers of the National Institute of Chemistry, Ljubljana and ICTM underlined in a recent publication in Polymer the unique mechanical properties of emulsion templated macroporous polymer foams consisting of poly(dicyclopentadiene). The recent work deals with the influence of surfactant loading on strengths and toughness of this kind of porous matter which can be considered as the strongest and toughest macroporous polymer foams available up to now.
Encapsulation of biomacromolecules in metal–organic frameworks (MOFs) can preserve biological functionality in harsh environments. Despite the success of this approach, termed biomimietic mineralization, limited consideration has been given to the chemistry of the MOF coating. In a collaborative contribution of researchers from the University of Adelaide, the Fudan University, the Elettra synchrotron and TU Graz studied the differences between enzymes encapsulated within different Zeolitic Imidazolate Frameworks. Bio-composites prepared with hydrophilic MAF-7 or ZIF-90 retain enzymatic activity under harsh environments (i.e. high temperatures, proteolytic agents, and organic solvents). Hydrophobic ZIF-8 affords inactive catalase and negligible protection to urease.
In a joint effort with Japanese and Australian scientists we have developed a high-throughput computational screening algorithm to identify MOFs that are likely to undergo macroscale aligned heteroepitaxial growth on a substrate. The ability to align porous metal–organic frameworks (MOFs) on substrate surfaces on a macroscopic scale is a vital step toward integrating MOFs into functional devices. But macroscale surface alignment of MOF crystals has only been demonstrated in a few cases. Screening of thousands of MOF structures by this process can be achieved in a few days on a desktop workstation. The algorithm filters MOFs based on surface chemical compatibility, lattice matching with the substrate, and interfacial bonding. Our method uses a simple new computationally efficient measure of the interfacial energy that considers both bond and defect formation at the interface. The according paper has been published in ACS Appl. Mater. Interfaces.
Dr. Paudel is Assistant Professor at the Institute of Process and Particle Engineering and scientific area leader at the Research Center Pharmaceutical Engineering GmbH where he is responsible for the development of novel products and innovative drug delivery approaches. His research focuses on poorly soluble, inhalative and oral drug delivery systems, individualized and personalized medicine and patient-centric formulations.
Prof. Paolo Falcaro is currently looking for three PhD students to address exciting challenges in the field of nano-porous functional materials. Candidates are encouraged to contact Prof. Falcaro for additional information.
On Sept. 21st 2018, the Advanced Materials Day which is the exhibition of research achievements of the FoE Advanced Materials Science took place. Three associate researchers (Bedoya, Hofmann and Ricco) gave lectures and six posters of associate researcher and PhD students (2x Vakalopoulou, Hengge, Kräuter, Kodolitsch) of Porous Materials@Work were presented.
42 researchers joined the event at Der Klugbauer. Such a team disclosed scientific skills and capabilities during 17 lectures. The aim and the progress of sub-projects were introduced during 10 short presentations given by PhD students. Thanks to the presence of the F&T house, an overview of available funding-schemes was given; particular emphasis was provided to funding-opportunities for pre- and postdocs.
This study shows that insoluble inorganic precursors and minerals can be used for the synthesis of porous crystals (Metal-Organic Frameworks - MOFs , specific MOF studied: HKUST-1). The proposed chemical process requires only water and ethanol as solvents; in presence of the second building-block of the porous crystal, the reaction spontaneously occurs at room temperature. Under these conditions, the original mineral rapidly decomposes and, simultaneously, a porous crystals forms. In other words, TU Graz, Adelaide University and CSIRO have found new “green” and fast procedure for the preparation of highly porous materials. The procedure is promising for industrial applications.
The aim of the interdisciplinary Marie-Curie project MNEMONIC (MagNetic Enzyme Metal OrgaNIc framework Composites) is to develop novel materials consisting of metal-organic frameworks (MOFs), magnetic nanoparticles (MNPs), and enzymes. The porous MOF coating protects proteins from inhospitable conditions, and provides a selective molecular gate for the exchange of substrates and products. External magnetic forces acts on the MNPs to allow for precise positioning in fluidic systems.
These composites will be synthesized using the recently discovered biomimetic mineralization process, in which metal ions and organic ligands can quickly nucleate on various biological substrates (proteins, DNA, cells), in aqueous solution at room temperature.
The long-term impact of this project includes technological benefits for industrial biotechnology, owing to the high resistance of MOF-coated enzymes towards organic solvents, high temperatures, and inhibitors, along with the presence of MNPs permitting easy localization and recovery of the material, convenient for highly automated processes.
This project is connected with the research proposed in the sub-task P11 of the Lead Project Porous Materials@Work.
The current research journal of Graz University of Technology just appeared.
Read the feature article entitled "Interior Architecture at the Nanoscale" written by Doris Griesser on the lead-project Porous Materials @ Work which will start on July 1st, 2018.
Researchers from ICTM will take part in three sub-projects dealing with conductive MOFs and COFs, microporous sensing materials towards optical sensing of methane and the synthesis and application of nanoporous zinc sulfide.
Oliver T. Hofmann received the START grant from the FWF. The Porous Materials@Work consortium cordially congratulates for this great achievement. Oliver T. Hofmann is an associate researcher of the lead-project and will contribute with his machine learning know-how in two sub-projects. We are looking forward working with him!
Karin Zojer will head the newly founded CD-laboratory for Mass Transport through Paper with the corporate partner Mondi Group on her side. Porosity is at centre stage of this CD lab. Karin Zojer states: ‘We want to understand the special pore structure of paper and be able to explain its influence on the transport of diverse types of particles through it. Only with this knowledge can the porosity of paper be swiftly and optimally adapted to the desired packaging application.’ Karin Zojer is associate researcher of the lead-project and with the foundation of the CD-lab, Porous Materials@Work will experience strong synergies concerning the modelling of porosity.