Category: Chemistry

by ARC Centre of Excellence in Exciton Science

Achieving photochemical upconversion in a solid state is a step closer to reality, thanks to a new technique that could unlock vital innovations in renewable energy, water purification and advanced health care.

Exciton Science researchers based at UNSW Sydney have demonstrated that a key stage in the upconversion process can be achieved in the solid state, making it more likely that a functioning device can be manufactured at commercial scale. Possible applications include hydrogen catalysis and solar energy generation.

Their work has been published in ACS Energy Letters and is likely to drive major changes in the approach of scientists around the world researching this challenging but potentially transformational field.

Professor Tim Schmidt of UNSW Sydney, an Exciton Science Chief Investigator and the senior author on the paper, said, “I think people are going to immediately start copying us. I consider this a breakthrough because this approach can be adapted to upconverting into the ultraviolet or from the infrared. There’s so much we can do with it.”

Upconversion involves gluing two low-energy photons of light together to create more energetic, visible light, which can be captured by solar cells or harnessed for other purposes.

The technical term for the gluing process is “triplet-triplet annihilation,” which produces a “singlet exciton.” An exciton is a quasiparticle which exists when an electron and the hole it is bound to becomes excited by light or another source of energy.

Controlled and reliable triplet-triplet annihilation and the photochemical upconversion it enables could raise the efficiency limit of solar energy devices from 33.7% to 40% or beyond.

Much of the fundamental research on upconversion is performed with liquid samples. For the mechanism to be useful in real-world devices applications, it must be effectively demonstrated in a solid state.

In this work, Exciton Science Research Fellow Dr. Thilini Ishwara and her colleagues created a thin film of nanostructured alumina stained with a sensitizer.

The pores of the structure are filled with emitter molecules in concentrated solution, which allows a highly promising photon generation quantum yield of 9.4%.

The next step for the researchers is to move beyond the concentrated solution used in this approach and to achieve similar results in an entirely solid state, potentially by using a gel-like substance.

“If you can make it small enough, you could use it for even doing chemistry in the body,” Thilini said.

“You can generate higher energy light at a targeted place inside the body to treat tumors or create medicines with laser precision.

“Water purification is another use for upconversion. If you can upconvert the visible spectrum into quite a harsh UV, you can kill bugs and save millions of lives each year in the developing world.”

Other applications potentially able to be powered by new upconversion techniques include infrared technology like night vision, and even 3D printing.

More information: Thilini Ishwara et al, Nanoporous Solid-State Sensitization of Triplet Fusion Upconversion, ACS Energy Letters (2023). DOI: 10.1021/acsenergylett.3c01678

Journal information: ACS Energy Letters 

Provided by ARC Centre of Excellence in Exciton Science

by Martha Höhne, Leibniz Institute for Catalysis

Wouldn’t it be an elegant solution to use the substance that is most damaging to the climate and threatens the future as a raw material for economic goods and everyday items? In fact, carbon dioxide (CO₂), an unavoidable byproduct of civilization, is already being used in the laboratory to produce lower olefins, alcohols and fuels in combination with hydrogen and other chemical reactants, all of which can be obtained sustainably. For such processes to become industrial practice, they must be able to run under “fluctuating” conditions.

“Fluctuating” means that these processes must also function with fluctuating supplies of energy and starting materials. This is new for chemistry, but cannot be avoided if the energy, for example for the production of hydrogen by electrolysis, is to come from renewable sources such as sun and wind in the future. These are not available continuously and not at all on windless nights.

However, the influence of dynamic conditions on chemical reactions has hardly been studied so far, as Prof. Dr. Angelika Brückner and Prof. Dr. Evgenii Kondratenko at the Rostock Leibniz Institute for Catalysis explain. Their research group is involved with work on developing catalysts for CO₂ hydrogenation to higher hydrocarbons under fluctuating conditions.

From climate gas to raw material

In the grand scheme of things, the goal is to replace petroleum as a raw material base and at the same time to ennoble a problematic waste gas, carbon dioxide, into a raw material. But CO₂ is an inert gas and hardly reacts on its own.

To obtain commercially useful compounds, especially basic materials for the chemical synthesis of valuable products, the extremely stable carbon-oxygen bonds in CO₂ must be activated. This is done catalytically by hydrogenation, i.e., hydrogen is added, which can produce a variety of different hydrocarbon compounds. The more carbon atoms they contain in the molecule, the higher their valence.

For the process, the chemists modified the so-called Fischer-Tropsch synthesis, which was developed almost a hundred years ago for the hydrogenation of carbon monoxide (CO). To do this, they replaced the highly toxic CO with CO₂.

Iron catalyst changes

The structure and properties of the catalyst play a key role in determining which products are formed during CO₂ hydrogenation. In the case of Brückner and Kondratenko, it is an iron catalyst. But not all iron is the same, they say. They discovered that the catalyst changes in the reaction under fluctuating conditions: It keeps forming new “phases and species” in between, they say.

To precisely distinguish between favorable and obstructive phases, the researchers observe the catalyst at work, so to speak. This is done using highly specific operando-spectroscopic analysis methods based on infrared, UV and laser light. The catalyst samples are partly developed by the researchers themselves and partly obtained from their research partner at the Humboldt University in Berlin.

Catalytically, iron is often used in the form of oxides, explains Prof. Kondratenko. “But we prefer to obtain methane with it.” With the molecular formula CH₄, methane is the main component in natural gas and the simplest hydrocarbon. “However, we are after higher-value hydrocarbons, currently, for example, olefins.” These are indispensable basic chemicals that can be further refined chemically.

Active catalytic phase: Iron carbide

The Rostock scientists discovered that one phase in particular is crucial for CO₂ hydrogenation, in which iron carbide is formed at the catalyst surface. And they learned how to stabilize this carbide phase and avoid the interfering phases. For example, by using iron oxalate, an iron salt of oxalic acid (FeC₂O₄), instead of the usual iron oxide as the catalyst material. The team recently published two articles on this topic in Catalysis Science & Technology and the Journal of Catalysis.

A third publication of the group, in ACS Catalysis, reports on the problem of the decreasing activity of the iron catalyst. As a cause, the Rostock chemists discovered intermediates that convert to coke under certain circumstances. This is deposited as a tough layer on the catalyst surface and obscures the active species.

For future plants, the vision would be to convert the carbon dioxide right where it accumulates en masse and use it as a raw material, say Prof. Dr. Brückner and Prof. Dr. Kondratenko. In accordance with the principles of green chemistry and the circular economy, such a process would be particularly suitable in the environment of the currently largest CO₂ emitters, such as the cement industry, iron and steel production and the chemical industry itself, where the CO₂ can be further processed with “green” hydrogen into valuable hydrocarbons.

More information: Qingxin Yang et al, The role of Na for efficient CO2 hydrogenation to higher hydrocarbons over Fe-based catalysts under externally forced dynamic conditions, Journal of Catalysis (2023). DOI: 10.1016/j.jcat.2023.07.012

Andrey S. Skrypnik et al, Spatial analysis of CO2 hydrogenation to higher hydrocarbons over alkali-metal promoted iron(ii)oxalate-derived catalysts, Catalysis Science & Technology (2023). DOI: 10.1039/D3CY00143A

Qingxin Yang et al, Understanding of the Fate of α-Fe2O3 in CO2 Hydrogenation through Combined Time-Resolved In Situ Characterization and Microkinetic Analysis, ACS Catalysis (2023). DOI: 10.1021/acscatal.3c01340

Journal information: ACS Catalysis 

Provided by Leibniz Institute for Catalysis 

by Zhang Nannan, Chinese Academy of Sciences

Researchers from the Shanghai Institute of Ceramics of the Chinese Academy of Sciences, together with collaborators, have made a significant breakthrough in electrocatalytic water splitting, a key technology for converting intermittent solar and wind energy into clean hydrogen fuel.

According to the study published in Science Advances, quinary high-entropy ruthenium iridium-based oxide holds promise for large-scale application in proton exchange membrane water electrolyzer (PEMWE).

In the pursuit of a hydrogen society, electrocatalytic water splitting has emerged as a potential solution. However, the acidic operating environment of the proton exchange membrane (PEM) has posed challenges for the long-term use of ruthenium oxide (RuO₂). Now, the researchers led by Prof. Wang Xianying have discovered a quinary high-entropy five-membered ruthenium iridium-based oxide (M-RuIrFeCoNiO₂), which has promising applications in PEMWE.

They developed a unique synthesis strategy for M-RuIrFeCoNiO₂ to create abundant grain boundaries (GBs). This innovation significantly improves the catalytic activity and stability of RuO₂ in acidic oxygen evolution reactions (OER), overcoming previous limitations.

The deliberate integration of foreign metal elements and GBs into the oxide catalyst played a pivotal role in improving OER activity and stability. This groundbreaking approach effectively solves the thermodynamic solubility problems associated with different metal elements.

Practical application tests showed remarkable results, as a PEMWE using the M-RuIrFeCoNiO₂ catalyst maintained a high current density of 1 A cm^-2 for more than 500 hours. This achievement marks a significant advancement in PEMWE technology and holds promise for the large-scale production of clean hydrogen fuel.

This study not only demonstrates a novel synthesis strategy for high entropy oxides, but also provides valuable insights into their activity and stability in the context of PEMWE, contributing to the advancement of clean energy solutions.

More information: Chun Hu et al, Misoriented high-entropy iridium ruthenium oxide for acidic water splitting, Science Advances (2023). DOI: 10.1126/sciadv.adf9144

Journal information: Science Advances 

Provided by Chinese Academy of Sciences 

by KeAi Communications Co.

The transfer of plastic waste from land to oceans and its subsequent accumulation within the food chain poses a major threat to both the environment and human health. Consequently, the development of renewable, low-cost and eco-friendly alternative materials has garnered tremendous attention and interest.

Starch is a highly desirable material for the production of bioplastics due to its abundance and renewable nature. However, limitations such as brittleness, hydrophilicity and thermal properties restrict its widespread application.

Addressing these concerns, a group of researchers from State Key Laboratory of Pulp and Paper Engineering at South China University of Technology presents a novel strategy for fabricating a fully bio-based starch plastic that exhibits numerous advantages, including superior flexibility, waterproof capability, excellent thermal processability and self-adaptability.

“Native starch exhibits great stiffness due to the strong hydrogen bonding between its molecular chains, resulting in challenges during thermal processing,” explains Xiaoqian Zhang, the first author of the study published in Green Energy & Environment. “A covalent adaptable network was constructed to effectively weaken the hydrogen bonding and improve the stress relaxation of starch chains.”

“In the production of the fully bio-based starch plastic, dialdehyde starch was subjected to a mild Schiff base reaction with a plant oil-based diamine. This reaction resulted in the formation of dynamic imine bonds, which exhibited the ability to be cleaved and reformed reversibly under heat stimulation. Consequently, the starch plastic demonstrated remarkable thermal processability,” Zhang said.

“Additionally, the presence of long aliphatic chains in the diamine enhanced the steric hinderance of the starch molecule chains, leading to improved flexibility and hydrophobicity of the starch plastic.”

Xiaohui Wang, corresponding author of the study, added, “Our transparent starch plastic, which contains imine bonds, also demonstrates self-healing capability. It can repair not only scratches but also large-area damage with a simple heat-pressing treatment.”

Notably, the self-healing efficiency reached more than 88% in terms of mechanical properties. Such desirable properties render the starch plastic highly appealing for various practical applications. “Through this study, we have successfully introduced a novel design strategy for developing sustainable, thermal processable, and degradable bioplastics using fully bio-based materials,” concluded Wang.

More information: Xiaoqian Zhang et al, Flexible, thermal processable, self-healing, and fully bio-based starch plastics by constructing dynamic imine network, Green Energy & Environment (2023). DOI: 10.1016/j.gee.2023.08.002

Provided by KeAi Communications Co.

by National Institute of Standards and Technology

In movies, when we see fiery car crashes or flaming planes on runways, we know they are not real. But in the real world, fuel fires must be quenched with special kinds of chemicals, and the ones that have been most commonly used are known as aqueous film-forming foams (AFFFs). However, environmental and health concerns about AFFFs have launched widespread efforts to detect, monitor and eventually eliminate them. Now, researchers at the National Institute of Standards and Technology (NIST) have released new reference materials to expedite these efforts.

What makes the foams so effective are chemical compounds called per- and polyfluoroalkyl substances (PFAS), enabling them to suppress fuel fires much more quickly and efficiently compared with other alternatives. Unlike water dumped on a flame, which wouldn’t work in a scenario where a flammable liquid is causing the fire, the foams not only spread over the fire but prevent it from reigniting by suppressing oxygen flow and fuel vapors. AFFFs were first introduced in the 1940s and have been used since that time not only in emergencies but also in firefighter training exercises.

Due to their significant ability to resist heat and chemical changes, the PFAS in these foams break down slowly over time, giving them the name “forever chemicals.” The foams can easily leak into nearby water and soil and affect the surrounding ecology, raising concerns because PFAS have been linked to negative health effects such as certain cancers.

Because of these concerns, organizations including the Department of Defense (DOD) are starting to eliminate the use of PFAS-containing materials. Under the 2020 National Defense Authorization Act, the DOD will be required to stop purchasing AFFFs from manufacturers by October 2023 and will stop using them by October 2024.

To help with this phaseout, NIST researchers have collaborated with the DOD on a series of AFFF reference materials (RMs) containing PFAS. During the phaseout process, older AFFFs will still be around, and the RMs will help organizations identify foams with PFAS so they can remove them from use.

While manufacturers aim to meet the new military specifications for their foams to contain less than 1 parts per million (ppm) PFAS, “There are still legacy AFFFs sitting across the country, and they will need to have measurements made to show if they contain PFAS,” said NIST chemist Jessica Reiner. “If they do contain PFAS, then they will need to be disposed of properly.”

NIST has released four RMs containing different formulations of PFAS in the foams: RM 8690 PFAS in AFFF I, RM 8691 PFAS in AFFF II, RM 8692 PFAS in AFFF III, and RM 8693 PFAS in AFFF IV are available from NIST.

“These four RMs contain many of the different PFAS used in the legacy AFFFs that are being phased out. The RMs are useful for labs that want to test for these,” said Reiner.

The RMs will also help the military when purchasing alternative fire suppressants.

“Because the military has to stop purchasing these foams, they need to test for PFAS in the new foams that they buy. By having these RMs, they can measure for PFAS. Manufacturers producing new foams could also use the RM when they need to test if they are PFAS free,” said Reiner.

NIST researchers sent the RMs to a number of other labs to be tested in what’s called an interlaboratory study. They learned scientists had a hard time measuring PFAS in foam form. NIST researchers then designed the new reference materials in a specific way so that each individual formulation is diluted to make it easier to use.

Analytical labs, academic institutions, and the U.S. Department of Transportation are a few other examples of groups that can use the RMs. “For example, anyone in a toxicology group could use these RMs for scientific experiments, such as delivering doses of the compounds to study their effects on cells,” said Reiner.

Provided by National Institute of Standards and Technology 

by Tsinghua University Press

A research group has synthesized a 2D copper-based complex and expanded it into a 3D structure by adding H4SiW12O40 and rare earth metal. Through this synthesis method the team obtained three isostructural 3d−4f metal-incorporated POMs.

The team then explored the application of these complexes in the fields of fluorescence and electrochemistry. They discovered that with their expanded structure, these complexes could be used as a fluorescence sensor to detect nickel cations (Ni2+), chromium (Cr3+), and nitrite (NO2–) and an electrochemical sensor to detect nitrite. This work holds potential applications in environmental monitoring.

Their work is published in the journal Polyoxometalates.

Polyoxometalates (POMs) have a broad variety of structures and functions that makes them one of the most versatile classes of inorganic molecular materials. They are formed by bridging oxygen atoms with transition metals in their oxidation states. Their potential applications are varied, including material science, catalysis, medicine, environmental protection, and hydrogen production.

However, because POMs dissolve easily in acidic or neutral solutions, their use in various applications is limited. One possible strategy to overcome this limitation is to combine POMs with metal ions to form metal complexes.

So the team synthesized the copper-based complexes from a 2D structure to a 3D structure by adding silicotungstic acid (H4SiW12O40) and rare earth metals. They employed a hydrothermal method that involved heating the crystals for an extended period and then cooling them, and also used a ligand containing nitrogen and carboxylic acid as a binder to extend the complex from 2D to 3D.

By adding the silicotungstic acid and rare earth metal (Ln3+), they successfully produced three 3d-4f bimetallic POMs complexes. In general, 3d-4f-metal complexes are coordination compounds consisting of transition metal ions and rare earth metals called lanthanides.

Next they characterized the purity, thermal stability, and optical and electrochemical properties of the three POM complexes they obtained. They used techniques including X-ray diffraction, infrared spectrum analysis, thermogravimetric analysis, and ultraviolet-visible absorption spectra analysis to study the complexes.

They chose one of the compounds (Cu-Sm-CP) to study as a sensor. They used the compound as a fluorescence probe to identify metal cations. The team investigated the compound’s ability to detect different metal ions in water at room temperature. They chose 13 metal ions for detection. They also used the compound for electrochemical sensing for nitrate.

Nitrate is a highly toxic substance that can easily form carcinogens in the human body and even leads to death. The team’s results showed them that Cu-Sm-CP has a potential application in the field of electrocatalysis and can be used as an electrochemical sensor material for nitrite detection.

“We synthesized three isostructural 3d-4f POMs and selected Cu-Sm-CP among them as fluorescence and electrochemical dual-function sensors to detect Cr3+ and Ni2+ using fluorescence sensing, as well as nitrite through electrochemical sensing,” said Wei Yao, with the University of Science and Technology Liaoning. In recent years, the detection of trace metal ions has attracted more and more attention because of the extremely toxic and acute poisoning caused by metal ions.

The team discovered that the Cu-Sm-CP exhibits remarkable fluorescence sensing capabilities, enabling them to identify Cr3+ and Ni2+ in aqueous solutions with exceptional recognition and anti-interference properties. “Finally, Cu-Sm-CP, as an electrochemical sensor, demonstrates excellent electrocatalytic performance for nitrite oxidation,” said Yao.

The team’s work not only provides a simple and feasible method for preparing 3d−4f metal-incorporated POMs complexes, but also provides effective materials for fluorescence sensing and electrochemical sensing.

Looking ahead to future research, the team hopes to expand their testing in real-world environmental conditions. “The next step is to detect the analyte in the actual environment, and finally complete the detection of harmful ions in living water, which has potential application value in environmental monitoring,” said Yao.

More information: Wei Liu et al, Structural extension of 2D complexes to 3D complexes and their applications, Polyoxometalates (2023). DOI: 10.26599/POM.2023.9140032

Provided by Tsinghua University Press

by Society of Chemical Industry

Scientists in China have fabricated a high-strength elastomer with self-healing properties. The polymer has significant potential in the field of flexible electronic devices.

In a study, published in Polymer International, researchers from a consortium of universities across Shanghai, China, have described a new poly(vinyl alcohol) (PVA)-based elastomer that can self-repair after damage, to maintain shape and performance. The flexible polymer is a solution to a longstanding issue with the durability of flexible electronic devices.

In recent years, flexible electronics have been attracting a lot of attention across multiple industries, with potential applications including flexible patch sensors to monitor blood glucose concentration, and flexible energy storage devices for wearable electronics. Currently however, the long-term stability of such materials is an issue, as Dr. Zili Li, Associate Professor at Fudan University, China, and corresponding author of the study, explained.

Speaking to SCI, he said, “Flexible polymer materials have been extensively explored in electronic devices, especially for health care and AI science. We want to solve the long-term reliability of the polymer matrix, which may be broken due to the external force damage, corrosion, or fatigue during operation.”

The study focuses on improving the properties of PVA, a polymer with excellent mechanical properties, but with poor stretchability and self-healing performance due to strong intramolecular and intermolecular bonds.

By using a one-step esterification reaction, the researchers added side chains onto the main PVA backbone, to create a graft polymer and subsequently incorporated Fe³⁺ ions into the matrix.

The resulting polymer had good stretchability (fracture elongation of 1565.0%) and self-healing performance (self-healing efficiency of 53.4% at room temperature) while maintaining excellent mechanical properties.

The team tested the performance of the graft polymer by coating the elastomers in a silver nanowire network to create a strain sensor. The resulting sensor exhibited high sensitivity and good self-healing performance. The authors noted that this result demonstrates “the wide potential applicability of the prepared PVA-based elastomers in health care, electrocardiography and safety monitoring.”

More information: Xingran Xu et al, Tailoring high mechanical performances of self‐healable poly(vinyl alcohol)‐based elastomers via judicious grafting of side chains, Polymer International (2023). DOI: 10.1002/pi.6515

Provided by Society of Chemical Industry

by Li Yuan, Chinese Academy of Sciences

A research group led by Prof. Lu Yi from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences (CAS) has proposed three-dimensional (3D) conductive polymer-hydrogel interpenetrating networks for high-performance chronic electrode/neural interfacing. The study was published in ACS Applied Materials & Interfaces.

Long-term, reliable detection of electrophysiological signals is pivotal for comprehending mechanisms that underlie brain disorders and for advancing effective treatments. Nonetheless, maintaining stability and biocompatibility of neural electrode interface for necessary extended periods remains challenging.

Poly (3,4-ethylenedioxythiophene), or PEDOT, is known for its excellent biocompatibility and low electrochemical impedance, making it a commonly used modified conductive polymer material in neural-electrode interfaces. However, PEDOT films often exhibit cracks or delaminations due to their limited electrochemical and mechanical stability, posing a significant challenge to the long-term viability of neural electrodes.

To address this issue, the researchers proposed a novel interface modification strategy in their work. They prepared a polystyrene sulfonate/polyvinyl alcohol (PSS/PVA) hydrogel film and applied it as a pre-coating on the surfaces of a microelectrode array, forming a 3D scaffold rich in counter ions.

Subsequently, they electropolymerized the 3, 4-ethylene dioxythiophene monomer within the PSS/PVA scaffold to create an interpenetrating conducting polymer network (ICPN). The resultant ICPN exhibited 3D highly porous microstructure, with pore sizes ranging from 0.1 to 1.0 μm.

This 3D porous structure plays a significant role in dissipating mechanical energy, enhancing adhesion, and ensuring the long-term stability of the conducting hydrogel coatings. Additionally, the ICPN film possesses a low Young’s modulus (191 kPa) and remarkable stretchability (72%).

The research team also discovered that this ICPN film featured low electrochemical impedance, high capacitance, and outstanding biocompatibility, meeting the requirements for neural interfaces in a wide range of in-vivo applications.

Furthermore, the researchers conducted a comparative analysis of the electrophysiological signal quality between ICPN and PEDOT/PSS film-modified neural electrode arrays after 12 weeks of implantation into the mouse hippocampus.

Their findings indicated that ICPN-modified interfaces significantly enhanced the quality of signals during chronic electrophysiological recordings.

The study holds potential to expand applications of neural implants and provides new insights into diagnosis and treatment of neuropsychiatric disorders in the future.

More information: Mengying Yan et al, Conducting Polymer-Hydrogel Interpenetrating Networks for Improving the Electrode–Neural Interface, ACS Applied Materials & Interfaces (2023). DOI: 10.1021/acsami.3c07189

Journal information: ACS Applied Materials and Interfaces 

Provided by Chinese Academy of Sciences 

by Chinese Society for Environmental Sciences

In a new study published in Environmental Science and Ecotechnology, researchers from Harbin Institute of Technology, have developed a novel double Z-scheme photocatalyst, called the molecularly imprinted TiO₂@Fe₂O₃@g-C₃N₄ (MFTC) composite, that selectively removes SMX from water.

Traditional photocatalytic methods have faced challenges with selectivity, often causing the indiscriminate degradation of organic pollutants and coexisting contaminants at high concentrations. However, the MFTC composite was purposefully designed to overcome this limitation by incorporating molecularly imprinted sites on its surface.

These specialized sites exhibit a unique ability to recognize and enhance the adsorption of sulfamethoxazole (SMX), making the MFTC highly effective in selectively targeting SMX in the presence of other pollutants like sulfadiazine (SDZ), ibuprofen (IBU), and bisphenol A (BPA). In simulated wastewater conditions, the MFTC composite impressively demonstrated a selective degradation efficiency rate of 96.8% for SMX, nearly twice as effective as competing catalysts for other pollutants.

The “lock and key” mechanism of the molecularly imprinted sites played a pivotal role in selectively capturing SMX, resulting in superior performance. The degradation process of SMX by the MFTC photocatalytic system involved the generation of •OH and •O₂⁻ free radicals, which facilitated the removal of SMX through a newly proposed double Z-scheme mechanism. This mechanism enhanced charge carrier transfer and separation, leading to significantly improved photocatalytic activity.

Moreover, the MFTC composite showcased remarkable stability and recyclability over multiple cycles, making it a promising and practical solution for water treatment applications. The exceptional performance and selectivity of the MFTC composite offer exciting prospects for the advancement of efficient and selective photocatalysts, contributing to the development of eco-friendly and cost-effective solutions for water purification and environmental remediation.

This research not only provides valuable insights into the selective removal of sulfamethoxazole (SMX) but also opens the door for further exploration of molecularly imprinted nanocomposite materials in selectively eliminating other pharmaceutical residues and organic pollutants.

More information: Jing-Yan Zhang et al, Selective removal of sulfamethoxazole by a novel double Z-scheme photocatalyst: Preferential recognition and degradation mechanism, Environmental Science and Ecotechnology (2023). DOI: 10.1016/j.ese.2023.100308

Provided by Chinese Society for Environmental Sciences

by Liu Jia, Chinese Academy of Sciences

Using solar energy to drive the cleavage of C-X bonds in halogenated organic compounds to form C-H bonds can not only control environmental pollution but also achieve important organic conversion reactions.

In a study published in ACS Applied Materials & Interfaces, a research group led by Prof. Cao Rong from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported a CdS/Zn(impim) coupled system in which the electron transfer kinetics of photocatalytic reduction of C-X bond for CdS/Zn(impim) composites has been explored.

The researchers synthesized CdS/Zn(impim) (MOF) dots-on-rods composite photocatalyst under mild conditions, and characterized the structure and morphology by powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and transmission electron microscope (TEM).

They found that CdS nanoparticles are uniformly loaded on the surface of rod-shaped Zn(impim) MOF, promoting the separation of electron-hole pairs.

To prove the direction of electron transfer from CdS to Zn(impim), the researchers measured the surface work functions by the Kelvin probe force microscope (KPFM). The fluorescence lifetime of CdS/Zn(impim) was significantly reduced compared to CdS. The related electron transfers kinetic was specified in detail by fluorescence spectrum and femtosecond transient absorption spectroscopy (fs-TAS).

In order to demonstrate the photocatalytic performance of CdS/Zn(impim), the researchers selected α-bromoacetophenone, bromobenzonitrile, and their derivatives as model reactions.

They revealed that the photocatalytic dehalogenation activity of CdS/Zn(impim) composite is much higher than that of CdS or Zn(impim) alone. The catalyst enjoyed good stability, and the morphology and structure of the catalyst did not change obviously after five consecutive cycles.

In the dehalogenation reaction of α-bromoacetophenone, the researchers detected the intermediate of acetophenone radical by electron paramagnetic resonance (EPR), proving the intermediate process of the reaction.

Under visible light irradiation, the electrons in CdS are excited and transferred to Zn(impim), and holes are retained in CdS, resulting in charge separation, thereby slowing down the charge recombination process and ultimately improving the efficiency of photocatalytic dehalogenation.

This study provides a further understanding of the electron transfer mechanism in semiconductor/MOF composites and the process of photocatalytic halide dehalogenation, and a feasible idea to design higher-performance photocatalytic materials.

More information: Yanan Feng et al, Rational Design of Electron Transfer Kineties of CdS/Zn(impim) Dots-on-Rods for Efficient Visible-Light Reduced C-X Bond, ACS Applied Materials & Interfaces (2023). DOI: 10.1021/acsami.3c07110

Journal information: ACS Applied Materials and Interfaces 

Provided by Chinese Academy of Sciences