Category: Chemistry

by Industrial Chemistry & Materials

Zeolites encapsulated metal and metal oxide species (regarded as metal@zeolite) are an important type of heterogeneous catalyst. They give performances that steadily outperform the traditional supported catalysts in many important reactions and have become a research hotspot. Remarkable achievements have been made dealing with the synthesis, characterization, and performances of metal species (typically metal and metal oxide clusters) confined in zeolites.

Although tremendous progress has been made with the synthesis, characterization, and catalysis of metal@zeolite catalyst, there remain many challenges that needed to be addressed. A team of scientists summarized the progress of metal@zeolite catalyst in recent years. Their work was published in Industrial Chemistry & Materials.

Metal catalysts are an important class of catalytic materials, which have been widely used in various chemical reactions such as redox, hydrogenation, and coupling reactions in the past few decades. It has been extensively reported in the literature that the small metal particle size contributes to greater exposure of active sites, as well as higher reactivity.

“However, small metal particles generally have low thermal stability and tend to sinter, coalesce, or leach under harsh reaction conditions, even when they have a strong interaction with supports. Therefore, deactivation due to sintering and leaching during the reaction process is one of the most important problems for the practical application of metal catalysts with small sizes,” said Zhijie Wu, a professor at the China University of Petroleum-Beijing.

Currently, confining metal species within graphene oxide, nanoporous carbon, metal-organic frameworks, and zeolite is a promising method to solve this problem.

Among them, zeolite has a high specific surface area, high thermal and hydrothermal stability, and adjustable acid-base properties, which has become an ideal support for confining highly dispersed metal species. In recent years, zeolites-encapsulated metal catalysts have been widely used in various catalytic processes, and their catalytic performance is steadily better than that of traditional supported catalysts, which has become a research hotspot.

Based on the origin of metal species within zeolites, three types of zeolite-encapsulated metal catalysts can be assigned. First, metal atoms embedded within the zeolite framework are removed and transferred into zeolite channels or pores via the calcination or reduction process.

Second, metal species without the capability to incorporate into a zeolite framework (e.g. Pt, Pd, or Ni) are introduced within zeolite micropores and then calcinated or reduced to encapsulated metal or metal oxides. Third, metal particles within the intra-crystalline mesopore of zeolites.

Two typical synthesis strategies for zeolite encapsulation, including post-treatment (i.e., ion-exchanging, interzeolite transformation, recrystallization, etc.) and in-situ synthesis (i.e., in-situ hydrothermal, dry-gel synthesis, etc.), have been developed. Specially, the in-situ hydrothermal synthesis and dry-gel conversion are frequently developed.

Because of the confinement effect within zeolite micropores, zeolite encapsulated metal or metal oxides show small size, even in sub-nanometer or atomic scale. Moreover, the geometric and electronic properties of encapsulated metal species are complex because of the strong metal-framework interaction.

Therefore, identifying metal particles confined in zeolites is challenging. Common characterization tools including X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy have been used to demonstrate whether the metal species are encapsulated in the micropores of zeolites.

However, these characterizations cannot reveal the fine structure of the metal species as well as the coordination environment in zeolite-encapsulated metal catalysts. Therefore, advanced characterization techniques such as spherical aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), X-ray absorption spectroscopy (XAS), and low-temperature CO infrared spectroscopy (CO-FTIR) have been developed to enable the study of the fine structure of the metal sites at the atomic level.

Encapsulation of metal species within zeolites is an attractive route to contain and maintain small and uniform metal clusters, to protect them against sintering and poisoning, and to select reactants, products, and transition states in catalytic reactions. However, the confinement of metal species within zeolites may also increase the diffusion barrier of reactant or product throughout the zeolite aperture, leading to a decreasing reaction rate somewhat.

Again, the confinement inevitably sacrifices some acid sites via the interaction between metal species with the zeolite framework. These together make the catalytic consequence of the zeolite-encapsulated metal catalysts complex which is varied with the reaction conditions.

“In the past decade, zeolite-encapsulated metal catalysts have been used in many catalytic processes and exhibit excellent performance. In this review, applications of metal@zeolite catalyst in hydrogen-related reactions were summarized,” said Wu.

There is still huge room for metal@zeolite in future development. Non-noble metals are more prone to agglomerate into large particles under the synthesis and reduction process. So far, zeolite-encapsulated ultra-small non-noble metal catalysts, especially those with high thermal stability, are still rarely reported.

Thus, effective methods to confine ultra-small non-noble metal clusters or single non-noble metal atom in zeolites is significant for developing efficient non-noble metal catalyst. In addition, the chemical states and coordination environment of metal species confined in zeolites may change in the reaction progress. In further research, more effects should be devoted to the development of in situ or operando characterization techniques and the design and optimization of the synergic effect between metal species and acid functions.

“Through this review, researchers can further understand the confinement effect of zeolites. At the same time, it provides a reference for designing zeolite-encapsulated metal catalysts with better performance,” said Wu

More information: Meng Liu et al, Recent advances in the synthesis, characterization, and catalytic consequence of metal species confined within zeolite for hydrogen-related reactions, Industrial Chemistry & Materials (2023). DOI: 10.1039/D3IM00074E

Provided by Industrial Chemistry & Materials

by Emily Caldwell, The Ohio State University

It turns out yogurt may have a previously unknown benefit: eliminating garlic odors.

A new study conducted in a lab—with follow-up human breath tests being planned—showed that whole milk plain yogurt prevented almost all of the volatile compounds responsible for garlic‘s pungent scent from escaping into the air.

Researchers tested the garlic deodorizing capacity of yogurt and its individual components of water, fat and protein to see how each stood up to the stink. Both fat and protein were effective at trapping garlic odors, leading the scientists to suggest high-protein foods may one day be formulated specifically to fight garlic breath.

“High protein is a very hot thing right now—generally, people want to eat more protein,” said senior study author Sheryl Barringer, professor of food science and technology at The Ohio State University.

“An unintended side benefit may be a high-protein formulation that could be advertised as a breath deodorizer in addition to its nutritional claims,” she said. “I was more excited about the protein’s effectiveness because consumer advice to eat a high-fat food is not going to go over well.”

The study was published recently in the journal Molecules.

Barringer has a history of identifying foods that can combat garlic breath, among them apples, mint and lettuce and milk, thanks to their enzymes and fat, respectively, that snuff out the sulfur-based compounds that cause garlic’s persistent smell.

After encountering speculation that yogurt might have a deodorizing effect, Barringer and first author Manpreet Kaur, a Ph.D. student in her lab, decided to check it out.

For each treatment experiment, the researchers placed equal amounts of raw garlic in glass bottles and confirmed the cluster of offending sulfur-based volatiles were released in concentrations that would be detected by the human nose. They used mass spectrometry to measure levels of the volatile molecules in gaseous form present before and after each treatment.

Results showed that yogurt alone reduced 99% of the major odor-producing raw garlic volatiles. When introduced separately, the fat, water and protein components of yogurt also had a deodorizing effect on raw garlic, but fat and protein performed better than water.

In the case of fat, a higher quantity of butter fat was more effective at deodorization. The proteins studied included different forms of whey, casein and milk proteins, all of which were effective at deodorizing garlic—likely because of their ability to trap the volatile molecules before they were emitted into the air. A casein micelle-whey protein complex performed the best.

“We know proteins bind flavor—a lot of times that’s considered a negative, especially if a food with high protein has less flavor. In this case, it could be a positive,” Barringer said.

Additional experiments involving changing the pH of the yogurt to make it less acidic—from 4.4 pH to 7 pH—reduced the yogurt’s deodorization effect on the garlic. Changing the pH of water, on the other hand, did not make any difference in water’s deodorization effect.

“That’s telling me it goes back to those proteins, because as you change pH you change the configuration of proteins and their ability to bind. That said we definitely should be looking at these proteins,” Barringer said. “It probably depends on the protein, as well, because different proteins react differently to pH. So that may be an important thing as we look at other proteins for their garlic deodorization effect.”

Barringer and Kaur tested the deodorizing effect of yogurt and its separate components on fried garlic as well, and in the process, they discovered that frying garlic alone significantly reduces most of garlic’s odor-causing volatile compounds. Yogurt and its individual ingredients neutralized a lower percentage of volatile compounds of fried garlic compared to raw garlic, presumably because there were fewer volatiles to trap than were present in the raw cloves, the researchers theorized.

The findings are a good foundation for future studies analyzing a variety of proteins that might be formulated into the perfect garlic-breath-reducing product and seeking to verify yogurt’s ability to curb actual garlic breath in people.

In the meantime, Barringer predicts that Greek yogurt, with a higher-protein profile than the whole milk plain yogurt used in the study, may be particularly effective at getting rid of garlic breath. Fruit-flavored yogurts will probably work, too, she said—and whatever is used, it must quickly follow ingestion of raw garlic.

“With apples, we have always said to eat them immediately,” she said. “The same with yogurt is presumed to be the case—have your garlic and eat the yogurt right away.”

More information: Manpreet Kaur et al, Effect of Yogurt and Its Components on the Deodorization of Raw and Fried Garlic Volatiles, Molecules (2023). DOI: 10.3390/molecules28155714

Provided by The Ohio State University 

by Cornell University

The number of molecules thought to exist is unfathomably large—somewhere between 10⁵⁰ and 10⁶⁰ (for comparison, there are only 10²² to 10²⁴ stars in the observable universe). The chemical and pharmaceutical sciences have sought a comprehensive understanding of the fundamental relationships in this vast “chemical compound space” that connects the structure of a given molecule and its properties.

Robert A. DiStasio Jr., associate professor of chemistry and chemical biology in the Cornell University College of Arts and Sciences, and collaborators at the University of Luxembourg and Argonne National Laboratory have conducted an extensive computational study of this space and have introduced a novel concept, called “freedom of design,” that can be used to identify molecules with targeted physical and/or chemical properties. The concept has important implications in the fields of rational molecular design and computational drug discovery.

Their paper, “‘Freedom of Design’ in Chemical Compound Space: Towards Rational in Silico Design of Molecules with Targeted Quantum-Mechanical Properties,” is published in Chemical Science.

One of the core findings from this international team of researchers was that most molecular properties are only weakly correlated and therefore effectively independent.

“While one might view this as a challenge in the field of rational molecular design, we demonstrate that this finding highlights an intrinsic flexibility—or ‘freedom of design’—that exists in the chemical compound space, wherein there are very few limitations which prevent markedly distinct molecules from sharing multiple important properties,” said DiStasio, a senior author on the paper.

To explore how this flexibility will manifest during the molecular design process, which often involves a “needle-in-a-haystack” search for molecules with a desired set of properties, the authors used “Pareto optimization” to identify potential candidate molecules for building polymeric batteries. In Pareto optimization, changing the molecule would not improve any of its properties without making another property worse.

The search was performed over a collection of molecules that was too large to catalog experimentally, and the results included many unexpected molecules, thereby reflecting the freedom available when designing molecules with targeted properties.

“A potentially interesting next step would be to use these Pareto-optimal structures in conjunction with powerful machine-learning approaches to build reliable multi-objective frameworks for a systematic navigation of hitherto unexplored swaths of chemical compound space,” said Alexandre Tkatchenko, professor of theoretical chemical physics at the University of Luxembourg and the study’s other senior author. “Such a development would enable us to rapidly identify the most promising molecules for next-generation chemical and/or technological applications.”

The insight provided by this work also forms the basis for an overall approach to the rational design of molecules and materials with targeted properties.

“Our understanding of structure-property relationships—the fundamental connections between the structure/composition of molecules and their emergent properties—is at the very heart of chemistry,” DiStasio said. “This work challenges one of the dominant paradigms in the field and begs the question: Which potentially transformative molecules are missed when we only consider modifying the functional groups on a largely fixed molecular scaffold?”

Other collaborators on this work were Leonardo Medrano Sandonas of the University of Luxembourg; Johannes Hoja of the University of Graz in Austria; Cornell doctoral student Brian G. Ernst; and Álvaro Vázquez-Mayagoitia of Argonne National Laboratory.

More information: Leonardo Medrano Sandonas et al, “Freedom of design” in chemical compound space: towards rational in silico design of molecules with targeted quantum-mechanical properties, Chemical Science (2023). DOI: 10.1039/D3SC03598K

Journal information: Chemical Science 

Provided by Cornell University 

by Eindhoven University of Technology

Woody biomass and wheat straw are all sources of the natural polymer lignin with more than 50 megatons of lignin produced annually at commercial scale. However, most is burned to produce energy, which alternatively could be used to make useful chemicals. A major issue with producing chemicals from lignin is that the properties of lignin vary from source to source and from season to season. Such variability can affect the yield and quality of the chemicals produced from lignin.

In a TU/e-led study, researchers have developed and tested a new and efficient model to predict the yield of lignin with specific chemical properties that are important for the production of biobased chemicals, materials, or fuels. The new study is published in Green Chemistry.

To date, most lignin derived from sources such as agricultural waste materials or woody biomass is burned to produce energy. As a renewable raw material, this can be seen as a waste. Researchers are looking for ways to use organic lignin as a reliable raw material for the chemical industry to make resins, foams, and biofuels.

As a source, woody biomass can be grown relatively fast, and thus it provides easy access to lignin for the long-term production of chemicals.

This is an idealized view of the situation though. “The major problem is that the properties of lignin are both unpredictable and variable, and this affects its usability,” says Mark Vis, assistant professor in the Department of Chemical Engineering and Chemistry and research lead.

So why is the unpredictability of lignin properties a bad thing? Vis explains, “Let’s say that we want to make a certain chemical using lignin, but we need lignin with a specific chemical composition to make the chemical. In any sample of lignin, there could be a million distinct types of lignin units, and isolating the right lignin type to make the chemical is the heart of the problem. Lignin does not have a single well-defined chemical structure, in contrast to the raw materials used to make conventional chemicals.”

The needle in a lignin stack

This sounds like searching for the proverbial needle in a lignin stack.

A treatment process known as solvent fractionation can help isolate the desired lignin types from the stack whereby lignin types with desired chemical properties are dissolved using a solvent, which later can be purified further by removing them from the solvent.

“Fractionation can decrease the range of lignin types, but with millions of lignin types in a sample, it’s difficult to be sure that a particular solvent will isolate a particular type of lignin,” says Vis. “Theoretical calculations can help predict the outcome of fractionation, but current theories are too complex to apply to lignin. And this is the problem that we solved.”

The solution from Vis and his collaborators at TU/e (including first author Stijn van Leuken and postdoc Dannie van Osch), Maastricht University, and the spin-off Vertoro is a new model that accurately and quickly predicts the fractionation of lignin in a solvent blend containing methanol and ethyl acetate. As it turns out, a blend is better for isolating precisely the lignin fraction needed.

Model times

The researchers’ model is based on the Flory-Huggins solution theory, a famous mathematical way of quantifying polymer solubility. Usually, this model is applied to study how one polymer interacts with a solvent, but the researchers took the model a number of steps further.

“Our model is well suited if you have hundreds of different polymer types simultaneously, which means that we can model the interactions of numerous lignin polymer types with different chemical properties (such as polymer chain length and composition) with the solvent,” says Vis. “Gaining insight on these interactions is critical as they affect whether a certain lignin type will dissolve or not in a certain solvent.”

To validate the new model, the researchers calculated the fractionation of lignin derived from wheat straw and then compared the model data with experiments involving the same materials. Vis adds, “We tested our model on existing data related to a common industrial lignin in a different solvent blend (methanol and dichloromethane). Our model was applied with minimal effort, and described the data very well,” adds Vis.

To date, in terms of using numerical tools to predict lignin yields, it’s all quite speculative. “Not many people are using theory to predict yields,” says Remco Tuinier, professor in the Department of Chemical Engineering and Chemistry and also an author on the paper. “Our model makes it easy and possible to predict which lignin can be isolated with a certain solvent (mixture). It’s a significant development for the field.”

Next steps

With the model proving so successful in predicting lignin yields, how can this model make an impact in industry? Panos Kouris, Chief Technology Officer and co-founder of Vertoro and co-author of the paper states, “This model is now a stepping stone for all lignin valorization activities; both in academia and industry.”

Vertoro is a spin-off company from a public-private partnership including TU/e, and wants to offer viable and affordable bio-based alternatives to fossil resources, so Kouris and his colleagues are well aware of the impact that the model can have on both academia and industry.

“In academia, the model can instigate new research lines on new solvents and lignin types, in addition to looking at ways to target particular lignin chemical properties for particular applications,” notes Kouris. “And in the biomass biorefining industry, the model could be very insightful and contribute to the design of new lignin-based products.”

Getting ready

In theory, the model can already be used by biorefineries to explore the valorization of certain lignin types, but there’s still a lot to be done before the model is ready for large-scale commercial use.

First, the model needs to be validated for the most common lignin types processed by the industry. Next, the solvent fractionation technology itself must have reached the level where the technology is ready for commercial use, and finally, clear applications of the final products are needed in the market, such as biobased packaging or biofuels.

Satisfying these requirements will take time, yet Kouris and his colleagues at Vertoro are optimistic that the model will have an impact on biorefineries sooner rather than later. “We at Vertoro expect that in the first half of 2024, the model will be extended to test several commercially available lignin sources, especially from second-generation cellulosic ethanol biorefineries that are actively looking for lignin valorization technologies and solutions.”

More information: Stijn H. M. van Leuken et al, Quantitative prediction of the solvent fractionation of lignin, Green Chemistry (2023). DOI: 10.1039/D3GC00948C

Journal information: Green Chemistry 

Provided by Eindhoven University of Technology 

by Chiba University

Transition metals form catalytic complexes that can speed up various chemical processes, especially in the production of pharmaceuticals as well as various pigments, dyes, and laboratory reagents like sulfuric acid. The use of light emitting diodes (LEDs) has boosted the use of visible light in reaction catalysis, and scientists have developed photo-redox catalysts made of iridium and ruthenium, which facilitate catalysis when irradiated with specific wavelengths of light.

Additionally, scientists have even demonstrated visible light photoreactions with palladium complexes without the use of photo-redox catalysts. While several such transition metal-catalyzed photoreactions have been developed, there has been limited development of new ligands for these reactions; most studies used existing ligands that were developed for thermal reactions.

Thus, there has been a notable lack of development of ligands that interact specifically with transition metal catalysts in photoreactions, preventing us from unlocking the true potential of such reactions.

Recently, a team of researchers, led by Professor Tetsuhiro Nemoto from the Graduate School of Pharmaceutical Sciences at Chiba University in Japan, developed novel ligands that can be used in photoreactions with transition metal catalysts. They also demonstrated how the developed ligands interacted with different transition metals to produce different catalytic results for photoreactions.

The team included Mr. Yu Matsuda from the Graduate School of Pharmaceutical Sciences at Chiba University and Dr. Masaya Nakajima, who was affiliated with the same institute at the time of the study but is now affiliated to the Graduate School of Pharmaceutical Sciences at the University of Tokyo. Their work was published in ACS Catalysis.

The researchers utilized commercially available 9-phenylacridine to prepare four acridine-containing PNP-pincer ligands, which were then used to create complexes with nickel, palladium, platinum, copper, and cobalt.

The team evaluated the catalytic activity of the complexes for a specific photoreaction called transfer hydrogenation, a common reaction used in various industries. While the nickel complex did not react efficiently, the palladium and platinum complexes successfully catalyzed the reaction to provide a high yield of the final products.

Specifically, the researchers found that the newly developed ligands allowed the platinum complex to successfully catalyze a reaction in the presence of visible light (blue LED irradiation) in a stoichiometric manner. This means that the exact values of reagents needed, and the quantity of product obtained, can be mathematically calculated.

The preciseness of the catalysis will allow the streamlining of industrial processes, such as in the production of medicines. Furthermore, the new platinum complex could catalyze the hydroxy/alkoxy alkylation of olefins—a reaction that could not be catalyzed with existing well-known ligands.

The fact that these photoreactions did not occur in the presence of well-known ligands highlights how the newly designed ligands could help define new reaction capabilities. Explaining the results, Dr. Nakajima says, “This research reveals a new reactivity of platinum that was previously unknown. As a result, it has become possible to synthesize new kinds of molecules more efficiently, potentially finding applications in the manufacturing of novel materials and pharmaceuticals.”

The present study is also expected to have numerous long-term implications. “Visible light is utilized as the energy source for such reactions. Thus, sunlight can be used as an endless source of energy, and technological advancement could allow us to perform photoreactions without the constraints that come with the arrangements necessary for thermal reactions, ultimately helping us resolve emerging energy issues,” concludes Dr. Nakajima.

Indeed, the development of new ligands for transition metal complex photocatalysis can create new possibilities and redefine reaction capabilities, allowing novel solutions to the challenges we face today.

More information: Yu Matsuda et al, Acridine PNP-Pincer Ligands Enabling Transition Metal-Catalyzed Photoreactions, ACS Catalysis (2023). DOI: 10.1021/acscatal.3c01654

Journal information: ACS Catalysis 

Provided by Chiba University 

by JooHyeon Heo, Ulsan National Institute of Science and Technology

The rapid advancements in flexible electronic technology have led to the emergence of innovative devices such as foldable displays, wearables, e-skin, and medical devices. These breakthroughs have created a growing demand for flexible adhesives that can quickly recover their shape while effectively connecting various components in these devices.

However, conventional pressure-sensitive adhesives (PSAs) often face challenges in achieving a balance between recovery capabilities and adhesive strength. In an extraordinary study conducted at UNIST, researchers have successfully synthesized new types of urethane-based crosslinkers that address this critical challenge.

Led by Professor Dong Woog Lee from the School of Energy and Chemical Engineering at UNIST, the research team developed novel crosslinkers utilizing m-xylylene diisocyanate (XDI) or 1,3-bis(isocyanatomethyl)cyclohexane (H₆XDI) as hard segments along with poly(ethylene glycol) (PEG) groups serving as soft segments. By incorporating these newly synthesized materials into pressure-sensitive adhesives, they achieved significantly improved recoverability compared to traditional methods.

The PSA formulated with H₆XDI-PEG diacrylate (HPD) demonstrated exceptional recovery properties while maintaining high adhesion strength (~25.5 N 25 mm⁻¹). Through extensive folding tests totaling 100k folds and multi-directional stretching tests spanning 10k cycles, the PSA crosslinked with HPD exhibited remarkable stability under repeated deformation—showcasing its potential for applications requiring both flexibility and recoverability.

Furthermore, even after subjecting the adhesive to strains up to 20%, it displayed high optical transmittance (>90%), making it suitable for fields such as foldable displays that demand not only flexibility but also optical clarity.

“This breakthrough in adhesive technology offers promising possibilities for electronic products that require both high flexibility and rapid recovery characteristics,” said Professor Lee. “Our research addresses the long-standing challenge of balancing adhesion strength and resilience, opening up new avenues for the development of flexible electronic devices.”

Hyunok Park, a researcher involved in the study, emphasized the significance of this research by stating, “The introduction of this new crosslinking structure has led to an adhesive with exceptional adhesion and recovery properties. We believe it will drive future advancements in adhesive research while contributing to further developments in flexible electronics.”

The study findings have been published in Advanced Functional Materials.

More information: Hyunok Park et al, Tailoring Pressure Sensitive Adhesives with H6XDI‐PEG Diacrylate for Strong Adhesive Strength and Rapid Strain Recovery, Advanced Functional Materials (2023). DOI: 10.1002/adfm.202305750

Journal information: Advanced Functional Materials 

Provided by Ulsan National Institute of Science and Technology 

by Chinese Academy of Sciences

The global energy crisis is exacerbated by the continuous consumption of fossil fuels during the rapid development of modern industries. In addition, the survival and development of human beings is also being seriously affected by the emission of greenhouse gases.

As we know, natural photosynthesis can convert solar illumination to sustainable energy. Inspired by this, a carbon-neutral strategy that uses sunlight to convert carbon dioxide to fuels has attracted great attention.

The successful implementation of photosynthesis depends on the design of photocatalysts. Inorganic semiconductors have been extensively studied for CO₂ photoreduction reaction (CO₂PRR), which presents shortcomings. For example, the band gaps of metal oxides and metal chalcogenides are difficult to adjust, resulting in poor light absorption. In addition, the high carrier recombination rate and the low Brunauer-Emmett-Teller (BET) specific surface area impair the photocatalytic efficiency, thus limiting photon utilization.

Photocatalysts based on porous organic frameworks (POFs) have attracted tremendous interest owing to their facile bandgap and charge separation tunability via designable functional building blocks. Nevertheless, a considerable portion of previously reported POFs still rely on the metal reactive sites. The photosensitizer and sacrificial reagent are required for promoting their performances on CO₂PRR.

These are obviously uneconomical. The photoreduction of CO₂ tends to produce mixed products with different ratios as the number of electrons and protons reacting with CO₂ varies. The quantity and purity of the targeted product are generally low due to insufficient conversion, which requires overcoming the high chemical inertness of CO₂. Therefore, achieving highly efficient and selective CO₂ conversion have been very challenging.

A research team led by Prof. Yong Yang from Nanjing University of Science and Technology and Prof. Yong Zhou from Nanjing University, China, reported a series of three-dimensional Tröger’s base-derived porous aromatic frameworks (3D-X-TB-PAFs (X = TEPE, TEPM, SPF)) featuring designated reaction sites and unique charge transfer properties. The results were published in Chinese Journal of Catalysis.

The incorporation of V-shaped Tröger’s base (TB) units and aromatic alkynes both endow polymers with permanent porosity, additional photon scattering cross-sections and enhanced CO₂ adsorption/activation capability. Both density functional theory (DFT) calculations and optoelectronic measurements reveal the formation of intramolecular built-in polarization and electron-trap sites brought about by TB, which modulate the charge separation and customize reaction sites in collaboration with the enhanced CO₂ accumulation.

Also, the product allocation in the photoreduction of CO₂ is hereby regulated together with the photooxidation of H₂O. Among the 3D-PAFs, the most efficient electron transport channel is constructed in TEPE-TB-PAF with the full conjugated TEPE-T.

In the absence of cocatalysts and sacrificial agents, TEPE-TB-PAF presents a competitive CO formation rate (194.50 μmol g^-1 h^-1) with near-unity selectivity (99.74%). Significantly, the low energy barrier for CO desorption and high energy barrier for *CHO formation commonly contribute to the high efficiency of TEPE-TB-PAF, which is demonstrated by computational explorations and in-situ diffuse reflectance infrared Fourier transform (DRIFT) spectra.

This work provides efficient building blocks for the synthesis of multifunctional organic photocatalysts and a ground-breaking insight for the simultaneous enhancement of photocatalytic reactivity and selectivity.

More information: Nan Yin et al, Tröger’s base derived 3D-porous aromatic frameworks with efficient exciton dissociation and well-defined reactive site for near-unity selectivity of CO2 photo-conversion, Chinese Journal of Catalysis (2023). DOI: 10.1016/S1872-2067(23)64474-2

Provided by Chinese Academy of Sciences 

by Kobe University

The Vilsmeier reagent is necessary for producing a large range of pharmaceuticals, but its unstable nature and toxic precursor phosgene are challenges for its use. A new process that efficiently produces phosgene, the Vilsmeier reagent and the desired products in one flow is poised to make the industry greener and safer.

For the production of many active pharmaceutical ingredients, a chemical called Vilsmeier reagent is necessary, but it is extremely unstable. That’s why it is produced on-site and on-demand wherever possible. In addition, the currently used methods for producing the reagent either use phosgene, which is itself an unstable and highly toxic chemical, or if phosgene is avoided result in toxic or difficult-to-remove by-products.

Kobe University chemist Tsuda Akihiko specializes on on-demand systems and using a unique UV-radiation approach, his group previously achieved the production of both phosgene and the Vilsmeier reagent from relatively safe and stable starting chemicals directly in the same vessel as their intended reaction substrates. This means they could achieve the whole reaction as if phosgene or the Vilsmeier reagent were never there.

While their technique was at first limited by being a batch process and thus being not easily scalable, they recently developed a completely novel flow system for the production of phosgene, creating an opportunity for the scalable on-demand production of other chemicals requiring phosgene. Tsuda explains, “Our group discovered for the first time that chloroform, a common organic solvent, underwent photochemical oxidation to form phosgene with high efficiency when irradiated with ultraviolet light. Our ‘photo-on-demand organic synthesis method’ based on this chemical reaction is a big step for phosgene-based organic synthesis.”

In a study published in the journal Organic Process Research & Development, the group adapted their unique process to create a flow system that produces the Vilsmeier reagent on demand from phosgene for direct reaction with any desired substrate. The phosgene was itself produced in the same on-demand flow system from chloroform, a relatively safe and stable starting compound, thus creating a scalable, safe and efficient reaction system to produce a wide range of useful chemicals.

“This reaction system consumes less energy, produces less waste, and enables versatile as well as scalable chemical synthesis. These features contribute positively to the life cycle assessment of the products, which is especially important in the industry,” comments Tsuda.

Thus, this process is a huge step into the direction of a safer and greener production of pharmaceutical chemicals. In addition, it also enables a more local production of these key chemicals, reducing dependence on production abroad.

More information: Yue Liu et al, Flow Photo-on-Demand Synthesis of Vilsmeier Reagent and Acyl Chlorides from Chloroform and Its Applications to Continuous Flow Synthesis of Carbonyl Compounds, Organic Process Research & Development (2023). DOI: 10.1021/acs.oprd.3c00267

Journal information: Organic Process Research & Development 

Provided by Kobe University 

by University of Bath

An ultraportable, low-cost device invented by researchers at the University of Bath proves highly successful at detecting synthetic cannabinoids (SCs, e.g. “Spice,” K2).

A device that lights up in the presence of illegal drugs soaked into paper or fabric is expected to be cleared for rollout across the U.K. within months.

The pocket-sized device is intended to detect SCs—a class of psychoactive substances used predominantly in prisons and homeless communities in the U.K. The drug can be fatal and often causes severe side effects, including psychosis, stroke and seizures.

The researchers hope that in its current format, the drug detector will be used to stem the flow of SCs smuggled into prisons and reduce the devastating effects on users of these highly addictive drugs. With further engineering, they are confident their device will be able to detect all types of synthetic drugs.

Professor Christopher Pudney, who led the research from the Department of Life Sciences at Bath, said, “Our device is truly groundbreaking—it’s battery-operated, ultra-portable, low-cost and gives instant results that anyone can interpret.

“Detecting Spice is a major challenge with currently available technology, not least because the substance is usually smuggled into prisons absorbed into physical products like paper and fabric, and now also in vape liquid, which makes detection very difficult.”

The device, and it’s potential to revolutionize the detection of SCs, is described this week in the journal Analytical Chemistry, published by the American Chemical Society.

National rollout

The researchers expect that the new tool—designed to light up in the presence of synthetic drugs—will be ready for mass production this autumn. The team is currently looking for a company able to manufacture the device at scale and distribute it to prisons, probation services, homeless shelters and relevant charities—initially in the U.K. but eventually also overseas.

SCs can be soaked into paper or other solid materials like clothing, and this has become a common way to smuggle it into institutions, as most detection technologies struggle to produce a reliable result when testing “complex” materials.

Professor Pudney said, “Typically, Spice enters prisons on paper, and once it’s inside, it’s divided into smaller paper sheets in the prison and then sold. The paper is crumpled up and inserted into a vape pen and smoked, so detection in the prison environment is incredibly challenging.”

The device is unique, being able to detect drugs on a very broad range of different materials and with high accuracy (95%). The team has even shown detection in vape liquid and the caps of vape pens.

“We see our device being used to decrease the amount of Spice used by all vulnerable communities, and we hope that leads to a better chance for people to recover from addiction and decrease serious health outcomes,” said Professor Pudney.

Instant detection

The device works by detecting the fluorescent properties that make up the core part of the synthetic cannabinoid molecule.

When the device touches a material that is suspected to contain an absorbed SC, it first identifies the material it’s on and then tests for the presence of the drug. An “alarm” shows up as a glowing ring of LEDs, visible to the operator to alert them to the presence of the substance. The greater the concentration of the SC, the brighter the LEDs glow.

Professor Pudney’s team is now working on modifying the device to detect more complex cross-conjugated compounds, including highly addictive benzodiazepines and opioids. They believe this objective may be achieved within the next two years.

Much more dangerous and unpredictable than cannabis

Spice was originally designed to mimic the effects of natural cannabis, but it is much stronger than cannabis, making it considerably more dangerous and unpredictable.

Recently, Spice has also been added to liquids in vapes, putting unsuspecting smokers at risk.

Generally, smokers are duped into smoking Spice when they have bought their vape liquid from a dealer and believe they are smoking vape liquid containing THC (one of the psychoactive substances extracted from cannabis) or cannabis oil. Even when hidden this way, however, the drug can be easily detected by the new device.

“We can spot Spice easily simply by opening a vape and testing the mouth filter,” said Professor Pudney.

More information: Gyles E. Cozier et al, Instant Detection of Synthetic Cannabinoids on Physical Matrices, Implemented on a Low-Cost, Ultraportable Device, Analytical Chemistry (2023). DOI: 10.1021/acs.analchem.3c01844

Journal information: Analytical Chemistry 

Provided by University of Bath 

by National University of Singapore

Spent coffee grounds (SCG) makes up the largest portion of waste generated from preparing coffee beverages and making instant coffee, producing close to 6 million metric tons of waste worldwide each year. To manage this vast amount of waste, scientists are finding ways of converting SCG into value-added products for various applications, from industrial materials to biofuels.

A team of researchers led by Associate Professor Liu Shao Quan from the NUS Department of Food Science and Technology under the Faculty of Science took a more innovative route to create an alcoholic beverage from fermented SCG as a way to sustainably manage the rising amount of waste generated from coffee consumption each year.

The team’s research on SCG-derived alcoholic beverages spanned across different studies where they worked on the flavor, aroma, and understanding its health benefits.

Achieving the best flavor and aroma

To prepare the alcoholic beverage from SCG, the researchers first prepared SCG hydrolysates, then fermented the SCG hydrolysates using a concoction of microorganisms, such as yeasts. Yeast plays an important role in the taste and aroma of the final product by influencing the chemical composition and quality of alcoholic beverages.

Assoc Prof Liu and his team demonstrated in a study published in 2021 in the journal LWT a method using two types of yeasts supplemented with yeast extracts for the fermentation process, allowing them to discover an effective way of creating an SCG-derived alcoholic beverage with a complex flavor palette.

“Alcoholic beverages are traditionally made using Saccharomyces yeasts. We took a different approach to making SCG-derived alcoholic beverages by exploring non-Saccharomyces yeasts for novel flavors and other characteristics,” said Assoc Prof Liu.

Following that study, the NUS team explored the use of other microorganisms, such as lactic acid bacteria with yeast, for fermentation to improve the smell and taste of the SCG-derived alcoholic beverage. The team used a mixture of yeast (Lachancea thermotolerans) and a lactic acid bacterium (Lactiplantibacillus plantarum) to ferment SCG hydrolysates to produce alcoholic beverages with different alcohol contents and physicochemical profiles.

This method resulted in higher contents of compounds related to a pleasant aroma and taste when compared to fermenting SCG hydrolysates with only yeast. The results of this fermentation strategy were published this year on 9 March 2023 in the journal Foods.

In their latest study, published in the journal Food Research International , the team adopted the fermentation strategy using this mixture of yeast and lactic acid bacteria for fermenting SCG hydrolysates. The team went a step further to conduct a detailed metabolomic analysis to identify the bioactive compounds present in the alcoholic beverage and determine its potential health benefits.

Identifying compounds that confer potential health benefits

The researchers adopted an advanced analytical technique known as liquid chromatography quadrupole time of flight mass spectrometry (LCQTOF-MS)—commonly used to identify and confirm the presence of chemical compounds in foods and beverages—to obtain a comprehensive picture of the chemical contents of the fermented SCG.

This study is the first time such an approach was used to determine a full profile of all the compounds present in SCG hydrolysates fermented by a combination of yeast and bacteria.

Through the analysis, the research team identified that fermentation of SCG hydrolysates through both yeast and bacteria boosted the presence of bioactive compounds associated with various health benefits, including anticancer, anti-inflammatory, and antimicrobial activities.

Dr. Liu Yunjiao, the first author of the most recent study, shared that the team developed several prototypes of the alcoholic beverages derived from SCG, all of which had varying flavor profiles.

“Some prototypes retained a coffee flavor, and for others, we’ve managed to achieve a pleasant flavor without a strong coffee flavor. Aside from the different flavor profiles, our tests showed that all the prototypes retained compounds that are known to confer health benefits, such as alkaloids and phenolic acids,” said Dr. Liu.

More information: Yunjiao Liu et al, Untargeted LC-QTOF-MS/MS-based metabolomics of spent coffee grounds alcoholic beverages fermented with Lachancea thermotolerans and Lactiplantibacillus plantarum, Food Research International (2023). DOI: 10.1016/j.foodres.2023.112733

Provided by National University of Singapore