Metal-organic framework nanoribbons

Metal-organic framework nanoribbons

The nanostructure of metal-organic frameworks (MOFs) plays an important role in various applications since different nanostructures usually exhibit different properties and functions. In this work, the authors reported the preparation of ultrathin MOF nanoribbons by using metal hydroxide nanostructures as the precursors. Importantly, this general method can be used to synthesize various kinds of ultrathin MOF nanoribbons. The as-prepared ultrathin nanoribbons have been used for DNA detection, exhibiting excellent sensitivity and selectivity.

Metal-organic frameworks (MOFs) have attracted great attentions in the past decades due to their many noticeable features, such as large surface areas, highly ordered pores, tunable structures and unique functions, making them promising for many applications. The structure engineering of MOFs at the nanometer scale is essential to customize MOFs for specific applications.

Among various nanostructures, ultrathin nanoribbons (NRBs) show great potentials in both fundamental studies and technological applications. Their unique features like high surface-to-volume ratio, highly active surface, and high concentration of selectively exposed crystal facets enable them to exhibit unique electronic structures, mechanical properties, and excellent catalytic efficiency. However, so far, the preparation of ultrathin MOF NRBs still remains a great challenge due to the complicated nucleation and growth processes of MOFs.

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Adding a polymer stabilizes collapsing metal…

Adding a polymer stabilizes collapsing metal-organic frameworks

Metal-organic frameworks (MOFs) are a special class of sponge-like materials with nano-sized pores. The nanopores lead to record-breaking internal surface areas, up to 7800 m2 in a single gram. This feature makes MOFs extremely versatile materials with multiple uses, such as separating petrochemicals and gases, mimicking DNA, hydrogen production and removing heavy metals, fluoride anions, and even gold from water—to name a few.

One of the key features is pore size. MOFs and other porous materials are classified based on the diameter of their pores: MOFs with pores up to 2 nanometers in diameter are called “microporous,” and anything above that is called “mesoporous.” Most MOFs today are microporous, so they are not useful in applications that require them to capture large molecules or catalyze reactions between them—basically, the molecules don’t fit the pores.

So more recently, mesoporous MOFs have come into play, because they show a lot of promise in large-molecule applications. Still, they aren’t problem-free: When the pore sizes get into the mesoporous regime, they tend to collapse. Understandably, this reduces the internal surface area of mesoporous MOFs and, with that, their overall usefulness. Since a major focus in the field is finding innovative ways to maximize MOF surface areas and pore sizes, addressing the collapsing problem is top priority.

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Enhancing the performance of metal-organic f…

Enhancing the performance of metal-organic framework materials

Researchers at the group of Dr. Stefania Grecea at the University of Amsterdam’s Research Priority Sustainable Chemistry have devised a way to enhance the practical performance of metal-organic frameworks (MOFs). By using leaves from the black poplar as a template, they produced hierarchical porous structures of mixed-metal oxide materials that can act as support for MOF crystals. In a recent edition of the journal ACS Applied Materials & Interfaces, Ph.D. student Yiwen Tang, in collaboration with Dr. David Dubbeldam of the UvA Computational Chemistry group, demonstrate the unique adsorption and separation properties of the bio-inspired design.

Separation of water-alcohol mixtures is one of the most challenging problems associated with the practical application of bioethanol as a sustainable fuel. Produced from agricultural feedstocks, algae farms or the fermentation of molasses, bioethanol contains both water and methanol as impurities. Obtaining fuel-grade bioethanol from these water-alcohol mixtures using traditional distillation is not practical because water and ethanol form a so-called azeotropic mixture.

The cost-effective and green alternative to distillation is adsorptive separation. In biofuels production, this method relies on the development of adsorbent materialswhich are highly selective towards ethanol or the impurities in the mixture. At the University of Amsterdam’s Research Priority Area Sustainable Chemistry, the group of Dr. Stefania Grecea develops synthetic approaches for designing porous molecular-based materials with such selective adsorption properties.

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Imperfection is OK for better MOFs

Imperfection is OK for better MOFs

Perfect crystals are not necessarily the most useful. Defects in the ordered crystalline structure of metal-organic frameworks (MOFs) could tailor these versatile materials for specific applications. KAUST researchers have already developed a pioneering method to image the defects using transmission electron microscopy. They now report that creating specific defects, visualizing them, and investigating their chemical effects takes the exploration of MOFs to new levels of detail and control.

MOFs contain regularly spaced metallic clusters connected by carbon-based organic linker groups. Varying the metals in the clusters and the structure of the linkers creates a huge diversity of MOFs with varying pore networks and different chemical properties. Two of the major applications MOFs are being developed for are for use as catalysts and as highly selective gas adsorption and separation materials.

MOFs are one of the hottest areas of chemical research, and KAUST scientists are hard at work to remain in the forefront. The latest advance builds on a long record of discoveries and has involved three KAUST research centers, the KAUST Core labs and collaborators in China and the UK.

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Building next gen smart materials with the pow…

Building next gen smart materials with the power of sound

Metal-organic frameworks, or MOFs, are incredibly versatile and super porous nanomaterials that can be used to store, separate, release or protect almost anything.

Predicted to be the defining material of the 21st century, MOFs are ideal for sensing and trapping substances at minute concentrations, to purify water or air, and can also hold large amounts of energy, for making better batteries and energy storage devices.

Scientists have designed more than 88,000 precisely-customised MOFs – with applications ranging from agriculture to pharmaceuticals – but the traditional process for creating them is environmentally unsustainable and can take several hours or even days.

Now researchers from RMIT University in Melbourne, Australia, have demonstrated a clean, green technique that can produce a customised MOF in minutes.

Dr Heba Ahmed, lead author of the study published in Nature Communications, said the efficient and scaleable method harnessed the precision power of high-frequency sound waves.

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New MOF rocket fuel to replace toxic, hazardou…

sci:

image

Today, most rockets are fueled by hydrazine, a toxic and hazardous chemical comprised of nitrogen and hydrogen. Those who work with it must be kitted up in protective clothing. Even so, around 12,000t of hydrazine is released into the atmosphere every year by the aerospace industry

Now, researchers are in
the process of developing a greener, safer rocket fuel based on metal organic
frameworks (MOFs), a porous solid material made up of clusters of metal ions
joined by an organic linker molecule. Hundreds of millions of connections join
in a modular structure.

image

Robin Rogers, formerly at
McGill University, US, has worked with the US Air Force on hypergolic liquids that
will burn when placed in contact with oxidisers, to try get rid of hydrazine.
He teamed up with Tomislav Friščić at McGill who has developed ways to react
chemicals ‘mechanochemically’ – without the use of toxic solvents.

The pair were interested in
a common class of MOFs called zeolitic imidazole frameworks, or ZIFs, which
show high thermal stability and are usually not thought of as energetic
materials.

image

They discussed the potential of using ZIFs with the imidazolate
linkers containing trigger groups. These trigger groups allowed them to
take advantage of the usually not accessible energetic content of these MOFs.

The resulting ZIF is safe
and does not explode, and it does not ignite unless placed in contact with
certain oxidising materials, such as nitric acid, in this case.

image

Authorities continue to
use hydrazine because it could cost millions of dollars to requalify new rocket
fuels, says Rogers. MOF fuel would not work in current rocket engines, so he
and Friščić would like to get funding or collaborate with another company to
build a small prototype engine that can use it.


To read the full article, by Kathryn Roberts, for free in C&I, the members’ magazine for SCI, click here.

Taming defective porous materials for robust…

Taming defective porous materials for robust and selective heterogeneous catalysis

The production of 1-butene via ethylene dimerization is one of the few industrial processes that employs homogeneous catalysis due to its high selectivity, despite the massive amounts of activators and solvents required. Now, a new paper by the University of the Basque Country (UPV/EHU), in collaboration with the López group at the Institute of Chemical Research of Catalonia (ICIQ) and RTI International, shows a more sustainable alternative via metal-organic frameworks (MOFs), a family of porous materials formed by metallic nodes connected through organic ligands.

The scientists demonstrate that tailored MOFs under condensation regimes catalyze the ethylene dimerization to 1-butene with high selectivity and stability in the absence of activators and solvent. The research, published in Nature Communications, opens new avenues to develop robust heterogeneous catalysts for a wide variety of gas-phase reactions.

The researchers engineered defects in the MOF (Ru)HKUST-1 without compromising the framework structure via two strategies: a conventional ligand exchange approach during MOF synthesis, and a pioneering post-synthetic thermal approach. The researchers then characterized the defects, which have been shown to be catalytically active for ethylene dimerization.

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Rocket fuel that’s cleaner, safer and …

Rocket fuel that’s cleaner, safer and still full of energy

Research published this week in Science Advances shows that it may be possible to create rocket fuel that is much cleaner and safer than the hypergolic fuels that are commonly used today. And still just as effective. The new fuels use simple chemical “triggers” to unlock the energy of one of the hottest new materials, a class of porous solids known as metal-organic frameworks, or MOFs. MOFs are made up of clusters of metal ions and an organic molecule called a linker.

Satellites and space stations that remain in orbit for a considerable amount of time rely on hypergols, fuels that are so energetic they will immediately ignite in the presence of an oxidizer (since there is no oxygen to support combustion beyond the Earth’s atmosphere). The hypergolic fuels that are currently mainly in use depend on hydrazine, a highly toxic and dangerously unstable chemical compound made up of a combination of nitrogen and hydrogen atoms. Hydrazine-based fuels are so carcinogenic that people who work with it need to get suited up as though they were preparing for space travel themselves. Despite precautions, around 12,000 tons of hydrazine fuels end up being released into the atmosphere every year by the aerospace industry.

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Regular

New biologically derived metal-organic framework mimics DNA

The field of materials science has become abuzz with “metal-organic frameworks” (MOFs), versatile compounds made up of metal ions connected to organic ligands, thus forming one-, two-, or three-dimensional structures. There is now an ever-growing list of applications for MOF, including separating petrochemicals, detoxing water from heavy metals and fluoride anions, and recovering hydrogen or even gold from it.

But recently, scientists have begun making MOFs, made of building blocks that typically make up biomolecules, e.g. amino acids for proteins or nucleic acids for DNA. Apart from the traditional MOF use in chemical catalysis, these biologically derived MOFs can be also used as models for complex biomolecules that are difficult to isolate and study with other means.

Now, a team of chemical engineers at EPFL Valais Wallis have synthesized a new biologically-derived MOF that can be used as a “nanoreactor” – a place where tiny, otherwise-inaccessible reactions can take place. Led by Kyriakos Stylianou, scientists from the labs of Berend Smit and Lyndon Emsley constructed and analyzed the new MOF with adenine molecules – one of the four nucleobases that make up DNA and RNA.

The reason for this was to mimic the functions of DNA, one of which include hydrogen-bonding interactions between adenine and another nucleobase, thymine. This is a critical step in the formation of the DNA double helix, but it also contributes to the overall folding of both DNA and RNA inside the cell.

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Nanomaterials give plants ‘super&rsquo…

Nanomaterials give plants ‘super’ abilities

Science-fiction writers have long envisioned human¬-machine hybrids that wield extraordinary powers. However, “super plants” with integrated nanomaterials may be much closer to reality than cyborgs. Today, scientists report the development of plants that can make nanomaterials called metal-organic frameworks (MOFs) and the application of MOFs as coatings on plants. The augmented plants could potentially perform useful new functions, such as sensing chemicals or harvesting light more efficiently.

The researchers will present their results today at the American Chemical Society (ACS) Spring 2019 National Meeting & Exposition.

According to the project’s lead researcher, Joseph Richardson, Ph.D., humans have been introducing foreign materials to plants for thousands of years. “One example of this is flower dyeing,” he says. “You’d immerse a cut flower stem into some dye, and the dye would be taken up through the stem and penetrate into the flower petals, and then you’d see these beautiful colors.”

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