Category: Chemistry

Boron, carbon, nitrogen and oxygen: these four elements can form chemical triple bonds with each other due to their similar electronic properties. Examples of this are the gas carbon monoxide, which consists of one carbon and one oxygen atom, or the nitrogen gas in the Earth’s atmosphere with its two nitrogen atoms.

Chemistry recognizes triple bonds between all possible combinations of the four elements—but not between boron and carbon. This is astonishing because there have long been stable double bonds between boron and carbon. In addition, many molecules are known in which triple bonds exist between two carbon atoms or between two boron atoms.

Chemists at Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, have now closed this gap: A team led by boron expert Professor Holger Braunschweig has succeeded for the first time in synthesizing a molecule with a boron-carbon triple bond, a so-called boryne, which exists as an orange solid at room temperature.

The scientists characterized the new molecule and also carried out initial reactivity studies. They present the results in the journal Nature Synthesis.

Boron atom in an uncomfortable situation

In the novel molecule, the boron atom is in a linear arrangement with carbon atoms. “In combination with the triple bond, this is about as uncomfortable as it gets for boron, requiring very special conditions,” says Dr. Rian Dewhurst, co-author of the study. This is why it has taken so long to synthesize such a triple bond for the first time.

What interests the Würzburg chemists about the new molecule: “Compounds in which individual atoms feel ‘uncomfortable’ often show a very interesting reactivity,” explains Maximilian Michel, the doctoral student who made the molecule in the laboratory.

It is precisely this reactivity that the team’s further work is now focusing on. Ultimately, this may result in innovative tools for chemical syntheses. The findings could also be helpful for a better understanding of chemical bonds and structures.

“Another benefit that is often overlooked: Basic research like ours inspires other researchers to put their efforts and imagination into synthesizing compounds that might seem improbable,” says Dewhurst. “World-changing advances often emerge from these kinds of crazy ideas.”

Teflon, for example, was discovered during research originally aimed at developing new refrigerants, while the well-known product superglue emerged by chance during attempts to produce transparent plastics.

More information: Maximilian Michel et al, The synthesis of a neutral boryne, Nature Synthesis (2025). DOI: 10.1038/s44160-025-00763-1. www.nature.com/articles/s44160-025-00763-1

Journal information: Nature Synthesis 

Provided by University of Würzburg 

Some beetles, such as Anomala albopilosa, strongly reflect left circularly polarized light (electromagnetic waves that oscillate leftward relative to the direction of light reception). This property originates from the formation of a cholesteric liquid crystal phase with an optically active, helical structure during chrysalis during exoskeleton formation and the solidification of this phase into a rigid skeleton while retaining its helical structure.

Researchers at the University of Tsukuba have coated the surface of its exoskeleton with an electrically conductive polymer, polyaniline. The polymer does not reflect circularly polarized light; however, electrical or chemical oxidation of the polymer changes its coloration, thereby changing its light transmittance.

By combining the color change caused by the oxidation and reduction of polyaniline with the exoskeleton’s properties of reflecting circularly polarized light, the researchers have crafted a new polymer element that can modulate the reflection intensity of the circularly polarized light. The work is published in the journal Next Materials.

First, the researchers examined the circularly polarized light reflectance of the exoskeleton. They confirmed that the green reflection of the exoskeleton is not caused by dyes, etc., but is a structural color (i.e., its coloration results from the reflection of light from the surface microstructure). They also confirmed that the exoskeleton strongly reflects left circularly polarized light.

Next, they coated the exoskeleton with polyaniline and created a polymer element with a two-layered structure comprising a conductive polymer and a sheath spring. For this coating, they measured the circularly polarized reflectance spectra of polyaniline in the oxidized state by doping it with ammonia and in the reduced state by dedoping.

They found that no circularly polarized light was reflected in the oxidized state. However, in the reduced state, left circularly polarized light was reflected. This research realizes a new bio/synthetic photofunctional material that combines the excellent optical properties of insects and the external field responsiveness of conductive polymers.

More information: Hiromasa Goto et al, Circularly polarized reflection spectra of a photonic beetle and preparation of tunable circularly polarized light reflecting device consisting of conductive polymer/beetle exoskeleton, Next Materials (2025). DOI: 10.1016/j.nxmate.2025.100516

Provided by University of Tsukuba 

Researchers in South Korea have developed a cobalt-iron (CoFe)-based non-noble metal ammonia decomposition catalyst, advancing eco-friendly hydrogen production. The work is published in the Chemical Engineering Journal.

The research team led by Dr. Su-Un Lee and Dr. Ho-Jeong Chae from the Korea Research Institute of Chemical Technology (KRICT) has successfully developed a high-performance ammonia decomposition catalyst by incorporating cerium oxide (CeO₂) into a cobalt-iron-based layered double oxide (LDO) structure. This innovation enables high ammonia decomposition efficiency at lower temperatures.

Ammonia (NH₃) is gaining attention as a carbon-free hydrogen carrier due to its high hydrogen storage capacity and transport efficiency.

However, extracting hydrogen from ammonia requires a high-temperature decomposition process, typically facilitated by catalysts. Ruthenium (Ru) catalysts demonstrate the highest efficiency in this reaction, but their high cost and the need for elevated temperatures pose significant barriers to large-scale application.

To overcome these challenges, the research team developed a CoFe-based non-noble metal catalyst enhanced with cerium oxide (CeO₂). This catalyst offers high ammonia decomposition efficiency at lower temperatures, ensuring cost efficiency and long-term stability.

Advantages of cerium oxide incorporation:

• Prevents particle agglomeration: Adjusts the surface structure of CoFe-based LDO catalysts, preventing metal nanoparticle sintering.
• Enhances catalytic properties: Utilizes Ce³⁺/Ce⁴⁺ redox transitions to modulate the electronic characteristics of the catalyst.

Facilitating the rate-determining step:

• The rate-determining step in ammonia decomposition is nitrogen recombination-desorption from the catalyst surface.
• The newly developed catalyst optimizes this process, significantly accelerating ammonia decomposition even at lower temperatures.

Thanks to these advancements, the catalyst achieved 81.9% ammonia conversion at 450°C, surpassing previous non-noble metal catalysts.

This marks a significant improvement compared to a 2022 nickel-based catalyst, which exhibited only 45% conversion at 450°C.

Furthermore, long-term stability tests at 550°C demonstrated that the catalyst maintained structural integrity and hydrogen production efficiency even after prolonged operation.

The research team aims to further enhance low-temperature hydrogen production efficiency through additional studies, targeting commercialization by 2030.

“This catalyst can be applied to large-scale ammonia-based hydrogen production, hydrogen power plants, hydrogen fueling stations, and maritime industries,” Dr. Su-Un Lee stated.

More information: Su-Un Lee et al, CeO2-conjugated CoFe layered double oxides as efficient non-noble metal catalysts for NH3-decomposition enabling carbon-free hydrogen production, Chemical Engineering Journal (2024). DOI: 10.1016/j.cej.2024.156986

Provided by National Research Council of Science and Technology 

How can we produce clean hydrogen without burning fossil hydrocarbons or other non-renewable energy sources? We can do so through photoelectrochemistry, or artificial photosynthesis, a method that—just like photosynthesis—uses sunlight and water, as with electrolysis, to obtain hydrogen, without generating harmful emissions. A group of researchers from the Department of Physics of the University of Trento has focused precisely on this approach.

The research is published in the journal Carbon.

One of the most innovative aspects of their research project is the use of photocatalysts (semiconductor materials) based on two-dimensional materials, and in particular, on graphitic carbon nitride (g-C₃N₄). This material is lightweight and sustainable and is used to break the chemical bond of the water molecules to produce hydrogen.

The research has shown that when used in the form of a single atomic layer, these photocatalysts offer superior performance compared to the thicker and less orderly structures previously tested. This discovery could open the way to a more efficient use of these materials in the production of green hydrogen.

Hydrogen is considered one of the most promising solutions for energy transition. But most hydrogen produced today is made via the “steam reforming” method, where methane (a fossil fuel) is heated to high temperatures; a process that is not fully sustainable. The Trento-based research team instead focuses on the production of hydrogen through photoelectrochemical cells.

This is a clean process that does not use hydrocarbons or other non-renewable energy sources to break the chemical bond of the water molecules to produce hydrogen.

“The graphitic compound based on graphitic carbon nitride has been suggested as a possible photocatalyst. In contact with water, this semiconductor absorbs visible sunlight and transforms it into chemical energy to allow the movement of electrons within matter. Before our work, little was known about these mechanisms,” explains Francesca Martini, lead author of the study.

“By studying the formation and propagation of excitons (a bound electron-hole pair), particles produced by sunlight in carbon nitride formed by a single layer of atoms, we realized that they have a very low speed and move in the photocatalyst thanks to a combined motion that includes the vibrations of the atoms.”

The authors of the study are surprised by this result. The electrons are more than two thousand times smaller than the atoms of the photocatalyst. Therefore, they move faster, just as a swarm of insects (the electrons) moves around a person (the atom). This, however, does not happen in carbon nitride. It is as if the swarm of insects agrees with the person to walk arm in arm like a couple, until they meet a hydrogen ion together.

“When this happens,” explains Matteo Calandra, study coordinator, “the atom bows and lets the electron that binds to the hydrogen ion pass through. Just as the father (the atom) of the bride (the electron) does when he takes her to the altar (hydrogen ion).”

The work of researchers will continue as they will perform numerical simulations on a database of over five thousand materials to which they have access, to perform a computational screening and identify better catalysts than the current ones.

“We hope that this research will lead to a strong innovation in the production of hydrogen from photoelectrolytic cells. Thanks to this methodology, we can now systematically identify better-performing materials and accelerate progress in the production of green hydrogen,” concludes Pietro Brangi, co-author of the study.

This project represents a significant step towards energy sustainability.

More information: Francesca Martini et al, Ultraflat excitonic dispersion in single layer g-C3N4, Carbon (2024). DOI: 10.1016/j.carbon.2024.119951

Journal information: Carbon 

Provided by University of Trento 

The world’s demand for alternative fuels and sustainable chemical products has prompted many scientists to look in the same direction for answers: converting carbon dioxide (CO₂) into carbon monoxide (CO).

But the labs of Yale chemists Nilay Hazari and James Mayer have a different chemical destination in mind. In a new study, Hazari, Mayer, and their collaborators present a new method for transforming CO₂ into a chemical compound known as formate—which is used primarily in preservatives and pesticides, and which may be a potential source of more complex materials.

The finding opens a new pathway for chemical discoveries, they say, and widens the possibilities for addressing environmental problems by transforming greenhouse gases into useful products.

The new study was published on March 7 in the journal Chem.

“Most of our fuels and commodity chemicals are currently derived from fossil fuels,” said Hazari, the John Randolph Huffman Professor of Chemistry, and chair of chemistry, in Yale’s Faculty of Arts and Sciences (FAS). “Their combustion contributes to global warming and their extraction can be environmentally damaging. Therefore, there is a pressing need to explore alternative chemical feedstocks.”

Hazari, who is also a member of the Yale Center for Natural Carbon Capture, and Mayer, the Charlotte Fitch Roberts Professor of Chemistry in FAS, are co-corresponding authors of the study. They are also part of the Center for Hybrid Approaches in Solar Energy to Liquid Fuels (CHASE), a solar energy research hub based at the University of North Carolina-Chapel Hill.

The challenges for transforming CO₂ into usable products—on an industrial scale—are formidable. Such processes require new catalysts that work under milder conditions (less extreme temperatures and pressures) and exhibit higher productivity and stability than currently available catalysts.

For the new study, the research team focused on a relatively under-explored type of catalytic system called an immobilized molecular catalyst. This is a system featuring a molecular catalyst that is attached to a solid support material.

The researchers developed molecular manganese catalysts that were attached to semiconducting, thermally oxidized porous silicon. When exposed to light, the silicon absorbs the light and transfers electrons to the manganese catalyst, which then converts CO₂ to formate.

“Formate is a very appealing product, as it is a potential stepping-stone to materials used industrially in very large quantities,” Mayer said. “Our work here opens the door to the use of readily available porous silicon as a support for molecular catalysts, in part because it establishes that the presence of a thin oxide layer improves catalyst selectivity and stability.”

The researchers had previously worked with hydride-terminated porous silicon, said Eleanor Stewart-Jones, a graduate student in chemistry at Yale and co-lead author of the study.

“There’s a rich literature studying the modification of porous silicon surfaces,” she said. “Knowing that these surface modifications can be used to tune catalysis will hopefully be impactful for future hybrid catalysts using porous silicon.”

The researchers also noted that the discovery may have applications for catalysts that work with other chemical feedstocks, beyond CO₂.

More information: Young Hyun Hong et al, Photoelectrocatalytic reduction of CO₂ to formate using immobilized molecular manganese catalysts on oxidized porous silicon, Chem (2025). DOI: 10.1016/j.chempr.2025.102462

Journal information: Chem 

Provided by Yale University 

Scientists have achieved the first real-time visualization of how excited-state aromaticity emerges within just hundreds of femtoseconds and then triggers a molecule to change from bent to planar structure in a few picoseconds.

By combining ultrafast electronic and vibrational spectroscopies, the team captured these fleeting structural changes at the molecular level and showed that aromaticity appears before—and then drives—the structural planarization. Their findings lay the groundwork for designing more efficient photoactive materials, such as sensors and light-driven molecular switches, by leveraging the power of aromaticity in excited states.

The study is published in the Journal of the American Chemical Society. The research was led by Hikaru Kuramochi, Associate Professor at the Institute for Molecular Science/SOKENDAI.

Aromaticity is a foundational concept in chemistry describing the enhanced stability of cyclic molecules whose electrons are delocalized. Although most discussions have focused on molecules in their ground state, the concept of excited-state aromaticity has recently been extensively utilized in predicting the structural change and designing the chemical reactivities induced by photoexcitation.

While the dynamic properties of excited-state aromaticity have been studied intensively in the past, these have primarily focused on molecules in a near-equilibrium state, leaving the precise timing and interplay between excited-state aromaticity and structural changes poorly understood. Directly visualizing these ultrafast motions is crucial for designing photoactive materials, such as sensors, adhesives, and switches.

The team used a combination of femtosecond transient absorption and time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS)—an advanced time-domain Raman technique that covers vibrational frequencies from terahertz to 3000 cm⁻¹ with femtosecond temporal resolution—to capture ultrafast snapshots of a newly synthesized cyclooctatetraene (COT)-based flapping molecule called TP-FLAP.

By exciting TP-FLAP with a femtosecond laser pulse, then probing its evolving vibrational signals, they could see exactly when and how the molecule’s central COT ring planarized. Isotope labeling with ¹³C at the central ring allowed the researchers to confirm which specific vibrational mode accompanied the bent-to-planar transition.

Initial measurements revealed a sub-picosecond (≈590 fs) electronic relaxation that imparts aromatic character to the bent molecule’s excited state. The molecule then undergoes planarization in a few picoseconds as indicated by a frequency shift in the ring’s carbon-carbon stretching vibration.

With the help of the isotope labeling (¹³C), a telltale shift in the key C=C stretching frequency was unambiguously shown, confirming that the ring’s planarization drives the observed vibrational changes. Calculations of aromaticity indices (e.g., nucleus-independent chemical shifts, NICS) further support that the system is already aromatic in the bent excited state and becomes even more aromatic as it undergoes planarization.

This study provides the first direct observation of nonequilibrium structural changes governed by excited-state aromaticity. It conclusively shows that aromaticity can emerge within hundreds of femtoseconds, preceding—and then facilitating—the picosecond-scale flattening of the molecule.

Beyond deepening our understanding of fundamental light-driven processes, these insights help guide the rational design of photoactive materials, including molecular sensors, tunable fluorescence probes, and photoresponsive adhesives. The TR-ISRS method’s ability to track vibrational modes in real time offers a new avenue for exploring other systems featuring excited-state (anti)aromaticity and complex conformational changes.

More information: Yusuke Yoneda et al, Excited-State Aromatization Drives Nonequilibrium Planarization Dynamics, Journal of the American Chemical Society (2025). DOI: 10.1021/jacs.4c18623

Journal information: Journal of the American Chemical Society 

Provided by National Institutes of Natural Sciences 

The environmentally harmful greenhouse gas carbon dioxide, or CO₂ for short, can be converted into valuable chemical products such as carbon monoxide (CO) or ethanol by means of electrochemical reduction—electrolysis. These can be used as raw materials for industry or for the sustainable provision of energy. However, a key obstacle to the long-term stability of this technology is the water and salt management within the electrolytic cell in which the chemical reaction takes place.

The research team led by Dr. Joey Disch and PD Dr. Severin Vierrath from Hahn-Schickard and the University of Freiburg, in collaboration with the French Institut Laue-Langevin in Grenoble, has made significant progress in understanding the distribution of water during CO₂ electrolysis. Their study was first published in the ACS Energy Letters and has now been featured as a Research Highlight in the February issue of Nature Catalysis.

The study uses high-resolution neutron imaging—one of the most powerful methods for directly investigating water transport in electrolyzers—to visualize the transport mechanisms during the pulsed operation of a CO₂ electrolyzer.

With a spatial resolution of 6 μm, this method allows a highly precise investigation of water distribution and salt formation under realistic operating conditions (400 mA cm⁻² at a cell voltage of 3.1 V and a Faradaic efficiency for CO of 95%). In contrast to X-rays, neutrons easily penetrate even metallic components, while making hydrogen and thus water-containing structures highly visible.

The results show a significant stabilization of the electrolyzer during pulsed operation, in which the cell potential is periodically set to a potential below the onset of reduction for a short time. Neutron imaging provides an explanation for the stabilization and illustrates that during the brief interruptions in operation, the water content in the gas diffusion layer increases, which promotes the breakdown of obstructive salt deposits.

Electrochemical CO₂ reduction opens up promising prospects for a sustainable transformation of the chemical industry. In particular, CO₂ electrolysis for the production of carbon monoxide is on the threshold of industrial application: Electrolysis cells with anion exchange membranes are already impressing with remarkable efficiency thanks to optimized reactant management and minimized resistance losses.

These findings thus provide valuable information for optimizing the design and operation of CO₂ electrolyzers, enhancing their efficiency and long-term stability, and facilitating the removal of the harmful greenhouse gas CO₂ from the environment.

More information: Luca Bohn et al, High-Resolution Neutron Imaging of Water Transport in CO2 Electrolysis during Pulsed Operation, ACS Energy Letters (2025). DOI: 10.1021/acsenergylett.4c03003

Marçal Capdevila-Cortada, Pulsed electrolysis through neutron lenses, Nature Catalysis (2025). DOI: 10.1038/s41929-025-01305-w

Journal information: Nature Catalysis  , ACS Energy Letters 

Provided by Hahn-Schickard

by Institute of Organic Chemistry and Biochemistry of the CAS

Researchers at IOCB Prague are the first to describe the causes of the behavior of one of the fundamental aromatic molecules, which fascinates the scientific world not only with its blue color but also with other unusual properties—azulene. Their current undertaking will influence the foundations of organic chemistry in the years to come and in practice will help harness the maximum potential of captured light energy. Their article appears in the Journal of the American Chemical Society (JACS).

Azulene has piqued the curiosity of chemists for many years. The question of why it is blue, despite there being no obvious reason for this, was answered almost 50 years ago by a scientist of global importance, who, coincidentally, had close ties with IOCB Prague, Prof. Josef Michl.

Now, Dr. Tomáš Slanina is following in his footsteps in order to offer his colleagues in the field the solution to another puzzle. He and his colleagues have convincingly described why the tiny azulene molecule violates the universal Kasha’s rule.

This rule explains how molecules emit light upon transitioning to various excited states. If we use the analogy of an ascending staircase, then the first step (the first excited state of the molecule) is high, and each subsequent step is lower and therefore closer to the previous one. The smaller the distance between the steps, the faster the molecule tends to fall from the step to lower levels. It then waits the longest on the first step before returning to the base level, whereupon it can emit light. But azulene behaves differently.

To explain the behavior of azulene, researchers at IOCB Prague used the concept of (anti)aromaticity. Again, simply put, an aromatic substance is not characterized by an aromatic smell but by being stable, or satisfied, if you will. Some chemists even refer to it informally with the familiar smiley face emoticon.

An antiaromatic substance is unstable, and the molecule tries to escape from this state as quickly as possible. It leaves the higher energy state and falls downward. On the first step, azulene is unsatisfied, i.e. antiaromatic, and therefore falls downward in the order of picoseconds without having time to emit light.

On the second step, however, it behaves like a satisfied aromatic substance. And that is important. It can exist in this excited state for even a full nanosecond, and that is long enough to emit light. Therefore, the energy of this excited state is not lost anywhere and is completely converted into a high-energy photon.

With their research, Slanina’s team is responding to the needs of the present, which seeks a way to ensure that the energy from photons (e.g., from the sun) captured by a molecule is not lost and that it can be further used (e.g., to transfer energy between molecules or for charge separation in solar cells).

The goal is to create molecules that manage light energy as efficiently as possible. Additionally, in the current paper, the researchers show in many cases that the property of azulene is transferable; it can be simply attached to the structure of any aromatic molecule, thanks to which that molecule gets the key properties of azulene.

Tomáš Slanina adds, “I like theories that are so simple you can easily envision, remember, and then put them to use. And that’s exactly what we’ve succeeded in doing. We’ve answered the question of why molecules behave in a certain way, and we’ve done it using a very simple concept.”

In their research, the scientists at IOCB Prague used several unique programs that can calculate how electrons in a molecule behave in the aforesaid higher excited states. Little is known about these states in general, so the work is also groundbreaking because it opens the door to their further study. Moreover, the article published in JACS is not only computational but also experimental.

Researchers from Tomáš Slanina’s group supported their findings with an experiment that accurately confirmed the correctness of the calculated data. They also collaborated with one of the world’s most respected authorities in the field of (anti)aromatic molecules, Prof. Henrik Ottosson of Uppsala University in Sweden. And this is the second time JACS has taken an interest in their collaboration; the first time was in relation to research on another primary molecule—benzene.

Yet the story of azulene is even more layered. It concerns not only photochemistry but also medicine. Like the first area, the second also bears the seal of IOCB Prague—one of the first drugs developed in its laboratories was an ointment based on chamomile oil containing a derivative of azulene.

Over the decades, the little box labeled Dermazulen, which contains a preparation with healing and anti-inflammatory effects, has found its place in first-aid kits throughout the country.

More information: David Dunlop et al, Excited-State (Anti)Aromaticity Explains Why Azulene Disobeys Kasha’s Rule, Journal of the American Chemical Society (2023). DOI: 10.1021/jacs.3c07625

Journal information: Journal of the American Chemical Society 

Provided by Institute of Organic Chemistry and Biochemistry of the CAS 

by Yongji Qin 

Hydrogen is widely recognized as a promising clean energy source, primarily due to its high energy density and the absence of carbon emissions during its utilization. This characteristic makes hydrogen an ideal candidate for addressing the growing energy demand and mitigating the environmental impact associated with the excessive use of non-renewable fossil fuels over the past decades.

To harness renewable energy from sources like solar, wind, and tidal power, a compelling strategy involves the conversion of this volatile energy into hydrogen. This approach not only aids in meeting the energy demand gap but also contributes to the overall sustainability of human society.

Presently, overall water splitting (OWS) is considered a viable method for hydrogen production. OWS, powered by renewable energy, facilitates the generation of hydrogen through the hydrogen evolution reaction (HER) on the cathode.

However, the Faradic efficiency of hydrogen production is impeded by the anodic oxygen evolution reaction (OER), which is characterized by sluggish kinetics and high thermodynamic potential.

Consequently, there is a pressing need for the development of advanced electrocatalysts for OER or other oxidation reactions with swift kinetics and low thermodynamic potentials.

An alternative approach gaining traction is overall hydrazine splitting (OHzS) for hydrogen production, leveraging the anodic hydrazine oxidation reaction (HzOR). HzOR exhibits fewer electrons and faster kinetics compared to OER, making it a promising avenue. Nevertheless, a significant challenge remains in the synthesis of bifunctional electrocatalysts for both HER and HzOR with low overpotentials.

Recently, a research team in China introduced a novel solution in the form of a two-dimensional multifunctional layered double hydroxide derived from a metal-organic framework sheet precursor. This material is supported by nanoporous gold, providing high porosity. The study is published in the journal Frontiers of Chemical Science and Engineering.

Remarkably, this electrocatalyst demonstrates dual appealing activities for both HER and HzOR. In practical terms, the OHzS cell exhibits superior performance, requiring only a cell voltage of 0.984 V to deliver 10 mA∙cm^-2, a notable improvement compared to the OWS system (1.849 V).

In addition, the electrolysis cell exhibits remarkable stability, operating continuously for more than 130 hours. This innovative approach not only enhances the efficiency of hydrogen production but also holds promise for a more sustainable and cleaner energy future.

by Liu Jia, Chinese Academy of Sciences

Glass can be synthesized through a novel “crystal-liquid-glass” phase transformation. Crystalline materials can be fine-tuned for desired properties such as improved mass transfer and optical properties through coordination chemistry and grid chemistry design principles.

However, how to induce the local structural disorder of crystalline materials to achieve glass transition remains a challenge because most of them undergo decomposition before melting.

In the metal-organic framework system, the exploration of glassy states is limited to a few model compounds such as ZIF-4, ZIF-62 and ZIF-8. There is a need to break the limitation of metals and ligands in the “crystal-liquid-glass” process and to develop the glass synthesis pathway of universal crystalline materials.

In a study published in Angewandte Chemie International Edition, a research group led by Prof. Zhang Jian and Prof. Fang Weihui from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported the meltable aluminum molecular rings with fluorescence and nonlinear optical properties.

Inspired by the characteristics of deep eutectic solvent (DES) mixtures involving significant depressions in melting points compared to their neat constituent components, the researchers designed and synthesized the first examples of meltable aluminum oxo clusters via lattice doping with DESs at the molecular level.

This kind of molecular ring compound undergoes a crystal-liquid-glass process after heating. The abundant and strong hydrogen bonds between the aluminum molecular ring, DES components and the lattice solvent in the structure are considered to be the root cause of the lower melting point. This lattice doping bonding method provides a general preparation method for the development of cluster glass.

The researchers determined the composition changes of the compounds before and after melting and quenching by modern characterization methods and in situ temperature monitoring (TG-IR-MS). They tried to mix DES solvent with an empty Al8 ring by physical doping, and found no melting phenomenon in the mixture after heating, which proves the importance of doping the DES component in the lattice, that is, DES component forms a “supracluster” structure with aluminum molecular ring.

Owing to the plasticity of the cluster glass “soft material,” the researchers explored its machinability and optical properties. They prepared the bubble-free glass film by a simple “hot pressing” method under atmospheric pressure, and well maintained the luminescence and third-order nonlinear effect similar to that of the original crystal.

The forming of this cluster glass film does not require additional mixed media, which is different from the traditional substrate bonding method, revealing the advantages of cluster glass.

This study demonstrates the potential of aluminum-related glass prepared by the third most abundant metal in the Earth’s crust, for sustainable development. The strategy combining the aluminum molecular ring and ionic liquid component overcomes the limitation of metal and ligand type of crystal glass, and provides a better approach for the study of “crystal-liquid-glass.”

More information: San-Tai Wang et al, Meltable Aluminum Molecular Rings with Fluorescence and Nonlinear Optical Properties, Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202400161

Provided by Chinese Academy of Sciences