Chemical Catalysis Research Articles

Actuating Liquid Crystals Rapidly and Reversibly by Using Chemical Catalysis.

Microtubules and catalytic motor proteins underlie the microscale actuation of living materials, and they have been used in reconstituted systems to harness chemical energy to drive new states of organization of soft matter (e.g., liquid crystals (LCs)). Such materials, however, are fragile and challenging to translate to technological contexts. Rapid (sub-second) and reversible changes in the orientations of LCs at room temperature using reactions between gaseous hydrogen and oxygen that are catalyzed by Pd/Au surfaces are reported. Surface chemical analysis and computational chemistry studies confirm that dissociative adsorption of H2 on the Pd/Au films reduces preadsorbed O and generates 1 ML of adsorbed H, driving nitrile-containing LCs from a perpendicular to a planar orientation. Subsequent exposure to O2 leads to oxidation of the adsorbed H, reformation of adsorbed O on the Pd/Au surface, and a return of the LC to its initial orientation. The roles of surface composition and reaction kinetics in determining the LC dynamics are described along with a proof-of-concept demonstration of microactuation of beads. These results provide fresh ideas for utilizing chemical energy and catalysis to reversibly actuate functional LCs on the microscale.

Synthesis and Properties of Novel Alkyl-Substituted Hexaazacyclophanes and Their Diradical Dications.

Radicals based on arylamine cyclophanes can be used as functional materials and show application potential in fields such as synthetic chemistry, molecular electronic components, organic light-emitting diodes, and catalytic chemistry. Using a Buchwald-Hartwig palladium-catalyzed aryl halide amination method, we synthesized a series of neutral hexaazacyclophane compounds 1-3 with different substituents in the meta-meta-meta positions of the phenyl rings. Three characteristic high-spin hexaazacyclophane diradical dications were obtained by two-electron oxidation using AgSbF6: 12·+•2[SbF6]-, 22·+•2[SbF6]-, and 32·+•2[SbF6]-. The electronic structures and physical properties of these compounds were then investigated by 1H and 13C nuclear magnetic resonance spectroscopy, cyclic voltammetry, electron paramagnetic resonance spectroscopy, superconducting quantum interferometry, ultraviolet-visible spectroscopy, and density functional theory calculations. The findings provide new ideas for designing radical species with novel physical properties and electronic structures. Importantly, the obtained radical species are not sensitive to air, making them valuable functional materials for practical applications.

Cerium oxide nanoparticles: Chemical properties, biological effects and potential therapeutic opportunities (Review).

The chemistry of pure cerium oxide (CeO2-x) nanoparticles has been widely studied since the 1970s, especially for chemical catalysis. CeO2-x nanoparticles have been included in an important class of industrial metal oxide nanoparticles and have been attributed a range of wide applications, such as ultraviolet absorbers, gas sensors, polishing agents, cosmetics, consumer products, high-tech devices and fuel cell conductors. Despite these early applications in the field of chemistry, the biological effects of CeO2-x nanoparticles were only explored in the 2000s. Since then, CeO2-x nanoparticles have gained a spot in research related to various diseases, especially the ones in which oxidative stress plays a part. Due to an innate oxidation state variation on their surface, CeO2-x nanoparticles have exhibited redox activities in diseases, such as cancer, acting either as an oxidizing agent, or as an antioxidant. In biological models, CeO2-x nanoparticles have been shown to modulate cancer cell viability and, more recently, cell death pathways. However, a deeper understanding on how the chemical structure of CeO2-x nanoparticles (including nanoparticle size, shape, suspension, agglomeration in the medium used, pH of the medium, type of synthesis and crystallite size) influences the cellular effects observed remains to be elucidated. In the present review, the chemistry of CeO2-x nanoparticles and their impact on biological models and modulation of cell signalling, particularly focusing on oxidative and cell death pathways, were investigated. The deeper understanding of the chemical activity of CeO2-x nanoparticles may provide the rationale for further biomedical applications towards disease treatment and drug delivery purposes.

Observation and Characterization of Vibrationally Active Surface Species Accessed with Nonthermal Nitrogen Plasmas.

Polycrystalline Ni, Pd, Cu, Ag, and Au foils exposed to nonthermal plasma (NTP)-activated N2 are found to exhibit a vibrational feature near 2200 cm-1 in polarization-modulation infrared reflection-absorption spectroscopy (PM-IRAS) observations that are not present in the same materials exposed to N2 under nonplasma conditions. The feature is similar to that reported elsewhere and is typically assigned to chemisorbed N2. We employ a combination of temperature-dependent experiments, sequential dosing, X-ray photoelectron spectroscopy, isotopic labeling, and density functional theory calculations to characterize the feature. Results are most consistent with a triatomic species, likely NCO, with the C and O likely originating from ppm-level impurities in the ultrahigh-purity (UHP) Ar and/or N2 gas cylinders. The work highlights the potential for nonthermal plasmas to access adsorbates inaccessible thermally as well as the potential contributions of ppm-level impurities to corrupt the interpretation of plasma catalytic chemistry.

Renaissance of Strong Metal-Support Interactions.

Strong metal-support interactions (SMSIs) have emerged as a significant and cutting-edge area of research in heterogeneous catalysis. They play crucial roles in modifying the chemisorption properties, interfacial structure, and electronic characteristics of supported metals, thereby exerting a profound influence on the catalytic properties. This Perspective aims to provide a comprehensive summary of the latest advancements and insights into SMSIs, with a focus on state-of-the-art in situ/operando characterization techniques. This overview also identifies innovative designs and applications of new types of SMSI systems in catalytic chemistry and highlights their pivotal role in enhancing catalytic performance, selectivity, and stability in specific cases. Particularly notable is the discovery of SMSI between active metals and metal carbides, which opens up a new era in the field of SMSI. Additionally, the strong interactions between atomically dispersed metals and supports are discussed, with an emphasis on the electronic effects of the support. The chemical nature of SMSI and its underlying catalytic mechanisms are also elaborated upon. It is evident that SMSI modification has become a powerful tool for enhancing catalytic performance in various catalytic applications.

Electronic interaction between biochar and montmorillonite toward enhanced peroxymonosulfate activation

Biochar works as the catalyst for activating peroxymonosulfate (PMS) to produce highly oxidizing radicals to remove organic contaminants from wastewater, but its activity requires further improvement. Recent research demonstrates that the PMS activation performance of biochar is closely related to the oxygen-containing functional groups (OFGs). Therefore, biochar/montmorillonite (BC/Mt) composites are designed for activating PMS toward degrading tetracycline. The negative charge of Mt. induced the electron transfer form Mt. to BC, which increases the nucleophilicity of CO groups that promote the activation of PMS to •OH and SO4•− radicals. Meanwhile, the pyrolysis path of rice straw is tuned by Mt., and the amount of COO groups is increased from 8.99% to 9.79% that promotes the generation of 1O2. Moreover, electron paramagnetic resonance and quenching experiments reveal that the activation mechanism of PMS by the BC/Mt. is comprised of both the radical and the non-radical pathway. Consequently, the tetracycline degradation kinetics using the optimized BC/Mt. (0.117 min−1) is higher than either bare BC (0.0866 min−1) or bare Mt. (0.0258 min−1), highlighting the significance of the rational design of electrocatalysts toward the enhanced catalytic chemistry. This work provides a facile route to improve the catalytic performance of biochar by hybridizing with clay minerals and is of great significance to promote the practical application of PMS-based advanced oxidation processes.

Nanoparticles: Role in the Chemical Industry, Potential Sources and Application in Chemical Catalysis

Chemical industries produce polymers, and with the help of nanotechnology, their structure can be modified to be used for other chemical applications and industrial processes. The chemical industry synthesized useful products and chemical compounds at great cost and with large amounts of energy required to produce them. In the article, the authors consider various approaches in the study of nanotechnology to improve chemical methods in order to increase their strength and performance. The role of nanoparticles and nanotechnologies in the processing of magnetic substances, the role in cleaning coatings and surfaces, and the role in the detoxification and filtration system of water are analyzed.

A novel µ-carbido hetero-binuclear iron-ruthenium heteroleptic complex on macrocyclic platforms with efficient oxidative activity

Bimetallic µ-bridged complexes supported by macrocycles are worth addressing due to their excellent stability, rich redox chemistry and suitability in catalysis. This paper for the first-time reports on the synthesis and redox properties of an unexplored heterometallic μ-carbido-dimer derivative bearing iron-porphyrin and ruthenium-phthalocyanine parts and a FeIV = C = RuIV unit. The compound is identified by UV–visible, IR, EPR, MALDI TOF, electrochemistry techniques and DFT calculations. The redox activity of the compound toward H2O2, tBuOOH is examined. The results indicate that under oxidation conditions in dichloromethane, benzene and acetonitrile, the initial complex evolves rapidly via oxidation steps forming intermediates which are competent in β-carotene and methylene blue oxidation at room temperature. The site oxidation accessibility of the initial compound and the nature of high-charged intermediate species are established to depend on the solvent polarity and axial ligands. The findings contribute to a deeper understanding of the significant role of reaction conditions as well as the mixed macrocyclic ligand environment and metal nature in controlling the oxidizing capability and thus can aid the development of new more active and durable catalysts.

Chemical Catalysis Guides Structural Identification for the Major In Vivo Metabolite of the BET Inhibitor JQ1.

The bromodomain inhibitor (+)-JQ1 is a highly validated chemical probe; however, it exhibits poor in vivo pharmacokinetics. To guide efforts toward improving its pharmacological properties, we identified the (+)-JQ1 primary metabolite using chemical catalysis methods. Treatment of (+)-JQ1 with tetrabutylammonium decatungstate under photochemical conditions resulted in selective formation of an aldehyde at the 2-position of the thiophene ring [(+)-JQ1-CHO], which was further reduced to the 2-hydroxymethyl analog [(+)-JQ1-OH]. Comparative LC/MS analysis of (+)-JQ1-OH to the product obtained from liver microsomes suggested (+)-JQ1-OH as the major metabolite of (+)-JQ1. The 2-thienyl position was then substituted to generate a trideuterated (-CD3, (+)-JQ1-D) analog having half-lives that were 1.8- and 2.8-fold longer in mouse and human liver microsomes, respectively. This result unambiguously confirmed (+)-JQ1-OH as the major metabolite of (+)-JQ1. These studies demonstrate an efficient process for studying drug metabolism and identifying the metabolic soft spots of bioactive compounds.

Integrative electrochemical and biological catalysis for the mild and efficient utilization of renewable electricity and carbon resources

Combining electrochemical and biological catalysis creates more suitable and efficient routes for the processing of renewable resources, such as CO2 and biomass.

Protein nanopore-based sensors for public health analyte detection.

High-throughput and label-free protein nanopore-based sensors are extensively used in DNA sequencing, single-protein analysis, molecular sensing and chemical catalysis with single channel recording. These technologies show great potential for identifying various harmful substances linked to public health by addressing the limitations of current portability and the speed of existing techniques. In this review, we provide an overview of the fundamental principles of nanopore sensing, with a focus on chemical modification and genetic engineering strategies aimed at enhancing the detection sensitivity and identification accuracy of protein nanopores. The engineered protein nanopores enable direct sensing, while the introduction of aptamers and substrates enables indirect sensing, translating the physical structure and chemical properties of analytes into readable signals. These scientific discoveries and engineering efforts have provided new prospects for detecting and monitoring trace hazardous substances.

Revealing microscopic dynamics: in situ liquid-phase TEM for live observations of soft materials and quantitative analysis via deep learning.

In various domains spanning materials synthesis, chemical catalysis, life sciences, and energy materials, in situ transmission electron microscopy (TEM) methods exert a profound influence. These methodologies enable the real-time observation and manipulation of gas-phase and liquid-phase reactions at the nanoscale, facilitating the exploration of pivotal reaction mechanisms. Fundamental research areas like crystal nucleation, growth, etching, and self-assembly have greatly benefited from these techniques. Additionally, their applications extend across diverse fields such as catalysis, batteries, bioimaging, and drug delivery kinetics. However, the intricate nature of 'soft matter' presents a challenge due to the unique molecular properties and dynamic behavior of these substances that remain insufficiently understood. Investigating soft matter within in situ liquid-phase TEM settings demands further exploration and advancement compared to other research domains. This research harnesses the potential of in situ liquid-phase TEM technology while integrating deep learning methodologies to comprehensively analyze the quantitative aspects of soft matter dynamics. This study centers on diverse phenomena, encompassing surfactant molecule nucleation, block copolymer behavior, confinement-driven self-assembly, and drying processes. Furthermore, deep learning techniques are employed to precisely analyze Ostwald ripening and digestive ripening dynamics. The outcomes of this study not only deepen the understanding of soft matter at its fundamental level but also serve as a pivotal foundation for developing innovative functional materials and cutting-edge devices.

Combinatorial Synthesis of Chiral Esters from Fruit Aroma in Continuous-Flow Reactors by Chemical and Enzymatic Catalysis

Short-chain chiral esters are important constituents in natural fruit flavors, as well as in food and pharmaceutical industries. Different chemical and bio-catalytic routes are used for their synthesis, but the use of simultaneous techniques has not been much explored, as combinatorial synthesis and bio-catalysis in continuous-flow systems. Here, the objective was to synthesize chiral esters typically found in fruit flavors, to obtain chemical libraries with high conversion and enantiomeric excess, using combinations of these three techniques. Combinatorial synthesis in continuous-flow coil-type reactors with fix bed was used in the esterification of the secondary alcohols 2-butanol (1a), 2-pentanol (1b), 3-hexanol (1c), 2-heptanol (1d) and 2-octanol (1e) with acetic (2) and propanoic (3) acids. A surface-response method was applied to optimize the reaction conditions. Conversions were above 88% after 60 min for the reaction with chemical catalysts in continuousflow reactors compared to 85%, but after 120 min, when conventional batch processes were used. By applying a biocatalyst, a chemical library of R acetates was prepared, with conversions over 48% after 48 h for batch and 40% after only 70 min for continuous flow reactions. It was observed that both enzymatic and homogeneous chemical catalysis showed to be viable for the chiral esters.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications.

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

X-type silyl ligands for transition-metal catalysis.

Given the critical importance of novel ligand development for transition-metal (TM) catalysis, as well as the resurgence of the field of organosilicon chemistry and silyl ligands, to summarize the topic of X-type silyl ligands for TM catalysis is highly attractive and timely. This review particularly emphasizes the unique σ-donating characteristics and trans-effects of silyl ligands, highlighting their crucial roles in enhancing the reactivity and selectivity of various catalytic reactions, including small molecule activation, Kumada cross-coupling, hydrofunctionalization, C-H functionalization, and dehydrogenative Si-O coupling reactions. Additionally, future developments in this field are also provided, which would inspire new insights and applications in catalytic synthetic chemistry.

Massive acceleration of SN2 reaction using the oriented external electric field.

Nucleophilic substitution is one of the most fundamental chemical reactions, and the pursuit of high reaction rates of the reaction is one of the ultimate goals in catalytic and organic chemistry. The reaction barrier of the nucleophilic substitution originates from the highly polar nature of the transition state that can be stabilized under the electric field created by the solvent environment. However, the intensity of the induced solvent-electric field is relatively small due to the random orientation of solvent molecules, which hinders the catalytic effects and restricts the reaction rates. This work shows that oriented external electric fields applied within a confined nanogap between two nanoscopic tips could accelerate the Menshutkin reaction by more than four orders of magnitude (over 39 000 times). The theoretical calculations reveal that the electric field inside the nanogap reduces the energy barrier to increase the reaction rate. Our work suggests the great potential of electrostatic catalysis for green synthesis in the future.

Multi-strategy study of environmental degradation of ibuprofen: From chemical catalysis to biological treatment

Ibuprofen, as one of the pharmaceuticals and personal care products, accumulates continuously in the environment with its increasing usage, posing pollution and potential threats to human health through various ways. Therefore, there is a pressing need to explore efficient methods for the degradation of ibuprofen. This paper primarily discusses current chemical and biological degradation approach of ibuprofen, explores the use of catalysts and degradation techniques in different degradation methods, and do comparative analysis of different degradation ways. The advantages and disadvantages of different methods in practice will be discussed and some problems which may encountered during the degradation process will be identified to provide references for further research on efficient degradation methods for ibuprofen.

Phosphonate-substituted porphyrins as efficient, cost-effective and reusable photocatalysts.

Recent advances in visible light photocatalysis represent a significant stride towards sustainable catalytic chemistry. However, its successful implementation in fine chemical production remains challenging and requires careful optimization of available photocatalysts. Our work aims to structurally modify bioinspired porphyrin catalysts, addressing issues related to their laborious synthesis and low solubility, with the goal of increasing their efficiency and developing reusable catalytic systems. We have demonstrated the catalytic potential of readily available meso-tetrakis[4-(diethoxyphosphoryl)phenyl]porphyrins (M(TPPP)). Novel metal (Pd(II), Co(II) and In(III)) complexes with this ligand were prepared in good yields. These chromophores were characterized in solution using spectroscopic (NMR, UV-vis, fluorescence) and electrochemical methods. The introduction of phosphonate groups on the phenyl substituents of meso-tetraphenylporphyrins (M(TPP)) improves solubility in polar organic solvents without significantly altering the photophysical properties and photostability of complexes. This structural modification also leads to easier reductions and harder oxidations of the macrocycle for all investigated complexes compared to the corresponding TPP derivatives. The free base porphyrin, zinc(II), palladium(II), and indium(III) complexes were studied as photocatalysts for oxidation of sulfides to sulfoxides using molecular oxygen as a terminal oxidant. Both dialkyl and alkyl aryl sulfides were quantitatively transformed into sulfoxides under blue LED irradiation in the acetonitrile-water mixture (10 : 1 v/v) with a low loading (0.005-0.05 mol%) of porphyrin photocatalysts, where H2(TPPP) and Pd(TPPP) were found to be the most efficient. The reaction mechanism was studied using photoluminescence and EPR spectroscopies. Then, to access reusable catalysts, water-soluble derivatives bearing phosphonic acid groups, H2(TPPP-A) and Pd(TPPP-A), were prepared in high yields. These compounds were characterized using spectroscopic methods. Single-crystal X-ray diffraction analysis of Pd(TPPP-A) reveals that the complex forms a 3D hydrogen-bonded organic framework (HOF) in the solid state. Both H2(TPPP-A) and Pd(TPPP-A) were found to catalyze the photooxidation of sulfides by molecular oxygen in the acetonitrile-water mixture (1 : 1 v/v), while only Pd(TPPP-A) resulted in selective production of sulfoxides. The complex Pd(TPPP-A) was easily recovered through extraction in the aqueous phase and successfully reused in five consecutive cycles of the sulfoxidation reaction.

The CO2 Conversion in a DBD Plasma: A 1D Synergistic Catalysis Model

Objective: Plasma catalysis is regarded as a promising technology in mitigating atmospheric CO2, but there is still a gap between industrial demand and current efficiency. This paper aimed to investigate the synergistic effect between vibrational states and catalyst surfaces in plasma catalysis, and to offer a theoretical guide on how to maximize the effectiveness of the synergistic effect in a more energy-efficient way. Methods: A novel 1D dielectric barrier discharge plasma catalysis model has been developed. The Arrhenius equations were used to solve the surface catalytic chemistry. The influence of CO2 vibrational excitation on surface reaction rates were expressed in the framework of the theoretical-informational approach. Results: The simulation suggested that a lower electron temperature fosters vibrational excitation, while a higher electron temperature promotes electronic excitation, therefore, the CO2 conversion rate and energy efficiency were difficult to be improved simultaneously. Furthermore, our model elucidates the pivotal role of catalysts in achieving efficient decomposition of vibrationally excited CO2 (CO2v). However, under conditions of low vibrational density, this synergistic effect fails to yield substantial improvements in catalytic efficiency under low vibrational density conditions. Conclusion: By increasing the pulse voltage, using narrow pulses with rapid rise times, implementing rapid cooling techniques and enlarging the surface catalytic area, the concentrations of CO2v can be augmented. Consequently, the dissociation rate via the V-V process and surface processes can both be enhanced, thereby potentially enabling simultaneous improvements in the CO2 conversion rate and energy efficiency.

Influence of the Weak Nuclear Force on Metal-Promoted Autocatalytic Strecker Synthesis of Amino Acids: Formation of a Chiral Pool of Precursors for Prebiotic Peptide and Protein Synthesis.

Natural chiral amino acids typically adopt an L structural configuration. While a preference for specific molecular chiralities is observed throughout biology and cellular chemistry, the origins of this preference are unclear. In a previous report the origin of enantiomeric selectivity was analyzed in terms of an "RNA World" model, and a pathway to a chiral preference for d-ribose was proposed based on the autocatalytic transformation of glyceraldehyde as a precursor to the formation of sugars. Metal-ion-promoted catalysis allows the parity non-conserving (PNC) weak nuclear interaction to influence the chirality of a nascent chiral carbon center. Since the PNC effect is the only natural property with an inherent handedness, it is an obvious candidate to influence enantiomeric preference from a catalytic reaction performed over geologically relevant time scales. The PNC influence requires and emphasizes the important role of catalytic metal ions in primordial chemistry. In this study, the impact of geologically available divalent calcium and higher Z alkaline earth elements are examined as mediators of chiral preference. Detailed calculations of the magnitude of the effect are presented, including the influence of time, temperature, pH, and metal ion identity. It is concluded that metal ions can direct chiral preference for amino acid synthesis via a metal-promoted autocatalytic Strecker reaction within a relatively short geological timeframe, thereby providing a pool of l-amino acids for catalytic chemistry evolving either from an RNA-world model of molecular evolution or alternative pathways to protein synthesis.