Catalytic Reaction Research Articles

Supramolecular PEG-DNA-Ferrocene Nanogels for Synergistically Amplified Chemodynamic Therapy via Cascade Reactions.

Chemodynamic therapy (CDT) has been limited by the tumor microenvironment, such as the low concentration of hydrogen peroxide (H2O2). The combination of therapeutic strategies that increase H2O2 with CDT can synergistically enhance the therapeutic effect. Herein, a novel supramolecular PEG-DNA-ferrocene nanogel that can codeliver glucose oxidase (GOx) and the hypoxia-activable prodrug tirapazamine (TPZ) was developed to synergistically amplify CDT via cascade reactions. The DNA nanogel was size-controllable and DNase I-responsive and exhibited good biocompatibility. Induced by oxygen consumption and H2O2 generation in the catalytic reaction of GOx, the drugs TPZ and ferrocene in the nanogel underwent the hypoxia-based reaction and the Fenton reaction, respectively. The vitro model tests, intracellular ROS test, MTT experiments, and DNA damage assay demonstrated that the H2O2-based cascade Fenton reaction and the hypoxia-based cascade reaction obviously increased ·OH generation and promoted the apoptosis of cancer cells. This cascade supramolecular nanoplatform provided a promising therapeutic strategy to synergistically amplify CDT.

Fuel-Driven Dynamic Combinatorial Peptide Libraries.

Dynamic combinatorial chemistry (DCC) creates libraries of molecules that are constantly interchanging in a dynamic combinatorial library. When a library member self-assembles, it can displace the equilibria, leading to emergent phenomena like its selection or even its replication. However, such dynamic combinatorial libraries typically operate in or close to equilibrium. This work introduces a new dynamic combinatorial chemistry fueled by a catalytic reaction cycle that forms transient, out-of-equilibrium peptide-based macrocycles. The products in this library exist out of equilibrium at the expense of fuel and are thus regulated by kinetics and thermodynamics. By creating a chemically fueled dynamic combinatorial library with the vast structural space of amino acids, we explored the liquid-liquid phase separation behavior of the library members. The study advances DCCs by showing that peptide structures can be engineered to control the dynamic library's behavior. The work paves the way for creating novel, tunable material systems that exhibit emergent behavior reminiscent of biological systems. These findings have implications for the development of new materials and for understanding life's chemistry.

Synergetic effect of iron and tungsten on molybdenum‐doped HZSM‐5 zeolite in catalytic methane dehydroaromatization

AbstractMethane dehydroaromatization is a viable route for production of carbon and valuable petrochemicals. Unlike Fischer–Tropsch and methanol synthesis processes which have been scaled up to commercial level, development of methane dehydroaromatization to commercial level has been hampered by various challenges. In this work, a 5.4 wt. % trimetallic (Fe‐W‐Mo/HZSM‐5) catalyst has been synthesized, characterized, and applied in catalytic methane dehydroaromatization reaction. A gas chromatograph was used to analyze both liquid and gaseous products from the reactor. Based on 0.0013 moles of reacted methane after 240 min time on stream at 750, GHSV 960 mlg‐1cath‐1, and atmospheric pressure, a 5.4% Mo/HZSM‐5 catalyst recorded 7.9% methane conversion, 10.6% C2 hydrocarbon selectivity, 51.8% benzene selectivity, 9.8% toluene selectivity and 27.8% coke selectivity. Doping Mo/HZSM‐5 with Fe reduced methane conversion by 4.0%, increased C2 hydrocarbon selectivity by 1.7%, reduced benzene selectivity by 6.2% and increased toluene and coke selectivity by 1.8% and 2.8% respectively. Doping Mo/HZSM‐5 with W increased methane conversion by 7.3%, reduced C2 hydrocarbon selectivity by 2.1%, reduced benzene selectivity by 7.6% and increased toluene and coke selectivity by 0.3% and 9.4% respectively. When iron and tungsten were loaded onto Mo/HZSM‐5, catalytic activity of the tri‐metallic catalyst in methane conversion reduced by 2.0%, C2 hydrocarbon selectivity increased by 2.7%, benzene selectivity reduced by 3.1%, toluene selectivity reduced by 3.7%, and coke selectivity increased by 4.1%. Therefore, this present work demonstrates that metal synergy in a tri‐metallic catalyst plays a role in methane conversion and selectivity towards useful hydrocarbons.

Density Functional Theory Study on Na+ and K+ Catalysis in the Transformation of Glucose to Fructose and HMF in Hydrothermal Environments

Hydrothermal carbonization (HTC) is an efficient method for converting biomass into biochar. Hydrochar contains catalytic components such as alkali and alkaline earth metals (AAEMs); however, the mechanisms by which highly active metals such as potassium (K) and sodium (Na) catalyze the conversion of small carbon–water compounds into hydrochar in hydrothermal environments remain unclear. In this study, glucose was used as a small molecule model, and Na+ and K+ were used as catalysts to investigate the catalytic reaction mechanism during the hydrothermal process using density functional theory (DFT). In the presence of different ions at various binding sites, glucose isomerizes into fructose, which subsequently undergoes three consecutive dehydration reactions to form 5-hydroxymethylfurfural (HMF). The results indicate that the catalytic effectiveness of Na+ and K+ in the isomerization of glucose to fructose is optimal when interacting with specific oxygen sites on glucose. For Na+, the interaction with the O1 and O2 oxygens provides the lowest reaction barrier of 37.16 kcal/mol. For K+, the most effective interactions are with the O3 and O4 oxygens and the O5 and O6 oxygens, resulting in reduced reaction barriers of 54.35 and 31.50 kcal/mol, respectively. Dehydration of fructose to HMF catalyzed by Na+ ions, the catalytic effectiveness at different positions is ranked as O5O6 > O1O5, whereas for K+, the ranking is O1O5 > O5O6. This study explores the catalytic effects of Na+ and K+ at different binding sites on the hydrothermal reactions of glucose at the atomic level, offering theoretical support for designing catalysts for the HTC of sludge.

Preparation of fly ash zeolite supported ZnO/Co3O4 catalyst for the photocatalytic degradation of xanthate under visible light

The development of high-value utilization technology of fly ash plays an important role in promoting environmental protection and social and economic development. In this paper, a novel composite photocatalyst Z-ZnO/Co3O4 is synthesized by loading ZnO/Co3O4 on the surface of fly ash zeolite. In addition, the properties of Z-ZnO/Co3O4 are characterized by variety of methods. The results show that the surface of cubic A-type zeolite is coated with ZnO/Co3O4 composite, forming an open spherical flower-like structure with a typical p-n heterostructure, which plays a positive role in reducing the band gap and the recombination rate of photogenerated electrons and holes of the composite catalyst, thus improving the degradation efficiency of xanthate. The degradation rate toward xanthate of Z-ZnO/Co3O4 is 97.62 % after simulated sunlight irradiation for 120 min under the optimum conditions, which is higher than that of Z-ZnO and Z-Co3O4, respectively. Meanwhile, the experimental results indicate that h+ plays a leading role in the catalytic reaction system. Furthermore, degradation rate toward xanthate of Z-ZnO/Co3O4 decreases slightly from 97.62 % to 88.24 % after five cycles, indicating its remarkable durability and stability.

Enhanced formaldehyde oxidation of plywood using MnO2 nanoflowers supported on porous hydrothermal carbon at ambient temperature

MnO2 nanoflowers were supported on porous hydrothermal carbon via in situ loading and used for the catalytic oxidation of formaldehyde from plywood manufactured with UF adhesive. The prepared MnO2 had a δ-type structure. The use of hydrothermal carbon (Hcs) improved the dispersion of active components in the materials and provided space for the catalytic reactions. Hcs/MnO2 exhibited catalytic activity and stability during formaldehyde oxidation at room temperature. The formaldehyde removal efficiency reached 90.43 % in 30 min. The Hcs/MnO2 had more oxygen vacancies than the MnO2 catalyst, providing more abundant active substances such as -OH, O2-, O- and other active substances to promote the catalytic reaction. The effects of Hcs/MnO2 on the formaldehyde emission and the mechanical properties of plywood were investigated. The MOR, MOE and bonding strength of the Hcs/MnO2-loaded plywood with 9 % Hcs were 51.1 MPa, 2994 MPa, and 0.8 MPa, respectively. After 28 d of exposure, the formaldehyde emitted from the plywood treated with Hcs/MnO2 decreased to 0.023 mg/m3, which fulfilled the requirement for ENF grading. The controlled release of free formaldehyde from plywood by Hcs/MnO2 was reflected by changes in mass transfer and catalytic oxidation. The manganese oxides in the micropores of the wood reduced the diffusion coefficient of free formaldehyde and hindered migration through the substrate. Once the concentration of formaldehyde decreased to a certain level, it was degraded by Hcs/MnO2, thus removing formaldehyde from the source.

Aptasensor based on cascaded fluorescent sensor assisted by exonuclease III for ultra-sensitive detection of Hg2.

Construct a sensitive and rapid detection fluorescence biosensor with the assistance of exonuclease III to achieve efficient detection of Hg2+. Nucleic acid aptamer H0 specifically recognizes Hg2+, and under the action of exonuclease III, H0 bound to Hg2+ is hydrolyzed, which in turn fails to trigger the catalytic hairpin self-assembly amplification reaction, resulting in a decrease in the number of double-stranded DNA bound to the fluorescent dye SYBR Green I in the solution, and a decrease in the fluorescence intensity. The results showed that the concentration of Hg2+ showed a good linear relationship with the fluorescence intensity of the sensing system within the range of 3.8-10pmol/L, and the detection limit was 0.53pmol/L. The recoveries of Xiangjiang River water used for the analysis of the actual samples were in the range of 99.57-103.58%, and the relative standard deviations of the determined values were 2.4-3.7%. The method is simple, sensitive, specific, cost-effective and can be applied to water samples.

Effect of Fe3+ or Fe2+ species on the catalytic performance and reaction pathway over CWK modified by iron sources in NH3-SCR reaction

Effect of Fe3+ or Fe2+ species on the catalytic performance and reaction pathway over CWK modified by iron sources in NH3-SCR reaction

Catalytic Impedance Spectroscopy: Concept and Application on CO2 Methanation.

Complex modeling of periodic excitation combined with time-resolved product detection is used to describe the complex response function of a catalytic system. We describe this concept of catalytic impedance spectroscopy (CIS) and the underlying general experimental approach and a concrete setup. The feasibility of CIS is experimentally demonstrated along the catalytic CO2 methanation reaction. The measurements confirm the theoretically anticipated rate-determining step of HCO* → CH* on Ni catalysts. Limitations and prospects of CIS to unravel reaction mechanisms are discussed.

Electric Field-Induced Enhanced Raman Spectroscopy Sensor and Photocatalysis with Thermoelectric-Plasmonic Metal Nanocomposites.

Electric field-induced surface-enhanced Raman scattering (E-SERS) substrates have been proven to further enhance the attained Raman intensity. Herein, integrated with plasmonic Ag nanoparticles (Ag NPs), the thermoelectric Bi2Te3 plate as an E-SERS substrate decreased the limit of detection by 2 orders of magnitude and increased the SERS signal by >20 times compared to those without electrical field induction. The thermoelectric potential produced by the Bi2Te3 plate could modulate the electron density and subsequently change the Fermi level of Ag. This increases the resonant electron transition probability using a broad range of molecules. The plasmon-activated catalytic reactions of the interconversion between p-nitrothiophenol and p,p'-dimercaptoazobenzene could be controlled through the E-SERS template. On the basis of the finite element method, explicit theoretical analysis indicated that the Ag NP-Bi2Te3-molecule charge transfer could improve our understanding of the SERS and photocatalytic mechanism.

Modulating the Hydrophilic‐Hydrophobic Microenvironment of MOF‐Stabilized Pt Nanozymes: the Role of H2O in the Peroxidase‐Like Catalyzed Reaction

Modulating the Hydrophilic‐Hydrophobic Microenvironment of MOF‐Stabilized Pt Nanozymes: the Role of H₂O in the Peroxidase‐Like Catalyzed Reaction

Tandem microplastic degradation and hydrogen production by hierarchical carbon nitride-supported single-atom iron catalysts

Microplastic pollution, an emerging environmental issue, poses significant threats to aquatic ecosystems and human health. In tackling microplastic pollution and advancing green hydrogen production, this study reveals a tandem catalytic microplastic degradation-hydrogen evolution reaction (MPD-HER) process using hierarchical porous carbon nitride-supported single-atom iron catalysts (FeSA-hCN). Through hydrothermal-assisted Fenton-like reactions, we accomplish near-total ultrahigh-molecular-weight-polyethylene degradation into C3-C20 organics with 64% selectivity of carboxylic acid under neutral pH, a leap beyond current capabilities in efficiency, selectivity, eco-friendliness, and stability over six cycles. The system demonstrates versatility by degrading various daily-use plastics across different aquatic settings. The mixture of FeSA-hCN and plastic degradation products further achieves a hydrogen evolution of 42 μmol h‒1 under illumination, outperforming most existing plastic photoreforming methods. This tandem MPD-HER process not only provides a scalable and economically feasible strategy to combat plastic pollution but also contributes to the hydrogen economy, with far-reaching implications for global sustainability initiatives.

Research on Denoising Algorithm of Standpipe Pressure Signal in FCC Device Based on Tortuosity and Denoising Intensity.

The pressure signal of the standpipe in the regeneration device for the catalytic cracking reaction is commonly used as a basis for equipment fault diagnosis. The device operates in environments of high temperature, strong vibration, and high flow rate. The standpipe pressure signal is easily interfered with by noise, making it difficult to extract pressure characteristics. In this study, a signal denoising algorithm based on pressure curve tortuosity and denoising intensity is proposed. A power spectrum threshold vector is utilized to filter the pressure in the circulating standpipe, and the denoising intensity and tortuosity after denoising are calculated. Taking the ratio of noise reduction intensity and tortuosity as the objective function, the noise reduction scheme of the pressure signal at different heights of the standpipe is determined. The denoised pressure signals are reconstructed, and the characteristic pressure signals of the circulating standpipe are extracted. The results indicate that the method suppressed the noise, enhanced the significance of characteristic parameters, and improved the accuracy of the fault diagnosis in the FCC units.

Reducing noble metal content in water electrolysis catalysts: A study on high-entropy oxides

This study presents the development of high-entropy oxide (HEO) catalysts based on Iridium-Ruthenium oxides (IrRuOx) for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWEs). By incorporating 3d transition metals such as Fe, Co, and Ni, we achieved catalysts with enhanced performance and stability. Using density functional theory (DFT) calculations, we predicted that HEOs possess a more favorable electronic structure for catalytic reactions. The synthesized rutile-type HEO catalyst (RuIrFeCoNi)O2, created via a molten salt oxidation method, exhibited a low overpotential of 261 mV and excellent cycling stability, maintaining a stable voltage of 1.73 V at 1 A cm−2 over 100 hours of electrolysis. This innovative approach not only reduces noble metal content but also leverages multimetallic synergistic effects to optimize the catalytic performance and stability, offering a promising avenue for the industrial application of acidic water electrolysis in PEMWEs.

Efficient synthesis of conjugated 2-(9H-fluoren-7-yl)-9H-fluorene via Br elimination in 2-bromofluorene using electron beam-irradiation

This study demonstrates the synthesis of conjugated 2-(9H-fluoren-7-yl)-9H-fluorene using electron beam irradiation within 3 min in place of the conventional catalytic cross-coupling reactions. 2-bromofluorene was irradiated at various doses (10, 30, 50, 70, 90, and 100 kGy), resulting in the elimination of Br from the 2-position and the formation of C–C bonds between the Br-eliminated fluorenes. The yield of 2-(9H-fluoren-7-yl)-9H-fluorene increased with higher absorbed doses, reaching 65% at 100 kGy. UV–Vis absorption of synthesized 2-(9H-fluoren-7-yl)-9H-fluorene showed an onset at 357 nm and a maximum absorption peak at 325 nm, and blue emission ranging from 340 to 450 nm in photoluminescence (PL). The results of UV–Vis absorption and PL indicated expanded conjugation of 2-(9H-fluoren-7-yl)-9H-fluorene due to the formation of C–C bonds between 2-bromofluorene through the electron beam-induced coupling reaction. Electron beam irradiation offers the potential to significantly reduce the reaction times for synthesis of conjugated organic compounds.

Mimicomes: Mimicking Multienzyme System by ArtificialDesign.

Enzymes are widely distributed in organelles of cells, which are capable of carrying out specific catalytic reactions. In general, several enzymes collaborate to facilitate complex reactions and engage in vital biochemical processes within cells, which are also called cascade systems. The cascade systems are highly efficient, and their dysfunction is associated with a multitude of endogenous diseases. The advent of nanotechnology makes it possible to mimic these cascade systems in nature and realize partial functions of natural biological processes both in vitro and in vivo. To emphasize the significance of artificial cascade systems, mimicomes is first proposed, a new concept that refers to the artificial cascade catalytic systems. Typically, mimicomes are able to mimic specific natural biochemical catalytic processes or facilitate the overall catalytic efficiency of cascade systems. Subsequently, the evolution and development of different types of mimicomes in recent decades are elucidated exhaustedly, from the natural enzyme-based mimicomes (immobilized enzyme and vesicle mimicomes) to the nanozyme-based mimicomes and enzyme-nanozyme hybrid mimicomes. In conclusion, the remaining challenges in the design of multifunctional mimicomes and their potential applications are summarized, offering insights into their future prospects.

The effects of different functional groups in Ni3-cluster MOFs on the efficient capture and transformation for flue gas CO2

As the greenhouse effect continuous increasing, the efficient CO2 capture and conversion into high-value fine chemicals have been necessary and meaningful. However, the CO2 coupling reaction always requires harsh catalytic reaction conditions and focuses on pure CO2 gas. Herein, three nickel-cluster metal-organic frameworks (MOFs) with different functional groups on the bridging-ligands have been synthesized and characterized structurally, presenting unique cages and channels architectural features. Catalytic investigations demonstrated that the amino-functionalized MOFs as a catalyst {[H2N(CH3)2]2[Ni3(µ3-O)(XN)(BDC-NH2)3∙7DMF}n (Ni3-NH2, XN = 6′′-(pyridin4-yl)-4,2′′:4′′,4′′′-terpyridine, H2BDC-NH2 = 2-aminoterephthalic acid) owns higher catalytic activity (96 %) than the other two in the CO2 transformation reaction with aziridine into oxazolidinones under 0.5 MPa within 4 h. Moreover, Ni3-NH2 can be reused at least ten times without significant catalytic activity loss under mild condition. Importantly, Ni3-NH2 catalyst still can be applicable to the simulating flue gas with 15 % CO2 as carbon source. The mechanism has been further revealed by NMR, FT-IR and DFT calculations, in which the Ni-site and the amino group can synergistically activate the substrate and CO2 molecule. This work has enriched the species of cluster-based MOFs and investigated the influence of characteristic functional groups on the catalytic activity deeply.

Illuminating tandem reactions characterized by temporal separation of catalytic activities via DFT calculations: A case study of Ni-catalyzed alkyne semi-hydrogenation

The concept of “temporal separation of catalytic activities” outlines a scenario where multiple transformations within a catalytic tandem reaction proceed sequentially over time without mutual interference. After presenting several examples of such reactions, we specifically focus on an example of the Ni-catalyzed alkyne semi-hydrogenation as a significant case study. By performing density functional theory (DFT) calculations, we illuminate the unique dynamic character of the reaction that the intermediate remains dormant until the reactant exhausted. The insights gained from the present calculations have led us to propose a comprehensive energy landscape model for the catalytic tandem reactions with temporal separation of catalytic activities, which offers a logical explanation for the temporal dormancy of the intermediate. This class of reactions is expected to be highly valuable as it presents the opportunity to fine-tune individual reaction steps, thereby introducing fresh concepts for precise control of reactions in one-pot chemistry.

In situ Generation of Cyclohexanone Drives Electrocatalytic Upgrading of Phenol to Nylon‐6 Precursor

AbstractCoupling in situ generated intermediates with other substrates/intermediates is a viable approach for diversifying product outcomes of catalytic reactions involving two or multiple reactants. Cyclohexanone oxime is a key precursor for caprolactam synthesis (the monomer of Nylon‐6), yet its current production uses unsustainable carbon sources, noble metal catalysts, and harsh conditions. Herein, we report the first work to synthesize cyclohexanone oxime through electroreduction of phenol and hydroxylamine. The Faradaic efficiency reached 69.1 % over Cu catalyst, accompanied by a corresponding cyclohexanone oxime formation rate of 82.0 g h−1 gcat−1. In addition, the conversion of phenol was up to 97.5 %. In situ characterizations, control experiments, and theoretical calculations suggested the importance of balanced activation of water, phenol, and hydroxylamine substrates on the optimal metallic Cu catalyst for achieving high‐performance cyclohexanone oxime synthesis. Besides, a tandem catalytic route for the upgrading of lignin to caprolactam has been successfully developed through the integration of thermal catalysis, electrocatalysis, and Beckmann rearrangement, which achieved the synthesis of 0.40 g of caprolactam from 4.0 g of lignin raw material.

Valence-engineered catalysis-selectivity regulation of molybdenum oxide nanozyme for acute kidney injury therapy and post-cure assessment.

The optimization of the enzyme-like catalytic selectivity of nanozymes for specific reactive oxygen species (ROS)-related applications is significant, and meanwhile the real-time monitoring of ROS is really crucial for tracking the therapeutic process. Herein, we present a mild oxidation valence-engineering strategy to modulate the valence states of Mo in Pluronic F127-coated MoO3-x nanozymes (denoted as MF-x, x: oxidation time) in a controlled manner aiming to improve their specificity of H2O2-associated catalytic reactions for specific therapy and monitoring of ROS-related diseases. Experimentally, MF-0 (Mo average valence 4.64) and MF-10 (Mo average valence 5.68) exhibit exclusively optimal catalase (CAT)- or peroxidase (POD)-like activity, respectively. Density functional theory (DFT) calculations verify the most favorable reaction path for both MF-0- and MF-10-catalyzed reaction processes based on free energy diagram and electronic structure analysis, disclosing the mechanism of the H2O2 activation pathway on the Mo-based nanozymes. Furthermore, MF-0 poses a strong potential in acute kidney injury (AKI) treatment, achieving excellent therapeutic outcomes in vitro and in vivo. Notably, the ROS-responsive photoacoustic imaging (PAI) signal of MF-0 during treatment guarantees real-time monitoring of the therapeutic effect and post-cure assessment in vivo, providing a highly desirable non-invasive diagnostic approach for ROS-related diseases.