Improve Reaction Efficiency Research Articles

An Update on the Recent Green Synthetic Approaches for Imidazo[1,2-a] Pyridine: A Privileged Scaffold

Abstract: Imidazo[1,2-a]pyridine is a fused bicyclic heterocycle that is known as a "drug prejudice" scaffold because of its numerous uses in organic and medicinal chemistry for the development of new drugs. As an outcome, numerous techniques for synthesizing this important class of compounds have been established. Some methods, however, are associated with toxic and corrosive catalysts, longer reaction times, poor yields, lower purity, and by-products in addition to the desired product. Green synthetic methods, which include microwave-assisted synthesis, catalyst-free, solvent-free, green solvent-based synthesis, mechanochemistry, and many others, are used to reduce the usage and production of harmful organic substances. These techniques improve reaction efficiency compared to conventional ones and also reduce the utilization and production of hazardous chemicals. Due to the implication of the imidazo[1,2-a]pyridine backbone as a biologically active ubiquitous fragment and the current demands of reducing toxic solvents, catalysts, and energy consumption, this review focuses on providing comprehensive highlights of the recent green synthetic pathways for imidazo[1,2-a]pyridine.

Mechanistic Insights into a Co(II)-Coordinated "Free" Metal Site of 2D Zinc-Based MOFs for β-Alkylation of Secondary Alcohols with Primary Alcohols.

Through in-depth study of the properties and reaction mechanisms of catalysts, it is possible to better optimize catalytic systems and improve reaction efficiency and selectivity. This remains one of the challenges in the field of catalysis. Therefore, the research and design of catalysts play crucial roles in understanding and optimizing catalytic reaction mechanisms. A robust 2D zinc-based MOFs (Zn-HA) supported Co(II) ion catalyst (Zn-HA@Co) has been designed and synthesized via a coordination-assisted strategy for β-alkylation of secondary alcohols with primary alcohols. The characterization demonstrated that the anchoring of Co(II) on Zn-HA via coordination could efficiently enhance the Co(II) ion dispersity and interaction between Co(II) and Zn-HA MOFs. Importantly, the density functional theory results have provided mechanistic insights into the energy of the HOMO and LUMO of the Zn-HA@Co catalyst as well as the energy change of the entire process after interacting with the reactants and the specific energy changes of each orbital. The synthesized Zn-HA@Co MOFs effectively lower the energy barrier of the catalytic reaction process. We expect that our research and design of catalysts will serve as valuable guideline for understanding and optimizing catalytic reaction mechanisms.

Streamlining efficient and selective synthesis of benzoxanthenones and xanthenes with dual catalysts on a single support

Using two catalysts on a single support can improve reaction efficiency, higher yields, improved selectivity, and simplified reaction conditions, making it a valuable approach for industrial transformation. Herein, we describe the development of a novel and effective heterogeneous catalyst, WCl6/CuCl2, supported on graphitic carbon nitride (W/Cu@g-C3N4), which was synthesized under hydrothermal conditions. The structure and morphology properties of the W/Cu@g-C3N4 were characterized using various spectroscopic techniques, including FTIR, XRD, TEM, TGA, EDX, and SEM. The W/Cu@g-C3N4 support material enabled the rapid and efficient synthesis of benzoxanthenones and xanthenes derivatives in high yields under mild reaction conditions and short reaction times. The W/Cu@g-C3N4 catalyst was also found to be easily recyclable, and its catalytic performance did not significantly decrease after five times use. The findings suggest that W/Cu@g-C3N4 is a promising chemical synthesis catalyst with significant implications for sustainable and cost-effective organic synthesis.

Photothermal contributions to H–Pd system

Temperature is one of the most critical parameters to control reaction process, increasing reaction temperature can promote the activity of the catalyst. Thus, a high priority will be to effectively accelerate the chemical reaction and improve the efficiency of chemical reaction by using appropriate means to raise reaction temperature. Herein, hydrogen-palladium (H–Pd) reaction, as a reversible reaction, is the internal physicochemical mechanism of Pd-catalyzed hydrogen purification and Pd-based hydrogen detection. According to temperature dependence of H–Pd reaction, it is significance to develop an H–Pd reaction temperature enhancement scheme to accelerate reaction and improve reaction efficiency, which is important to design/optimize Pd-based hydrogen sensor and understand the relationship between reaction course and temperature. Therefore, we demonstrate an all-optical H–Pd reaction temperature enhancement scheme assisted by photothermal effect. In addition, for analyzing the relation between H–Pd reaction and temperature, we designed an optics-mechanics coupling-based fiber hydrogen sensor, it can convert the influence of photothermal-induced reaction temperature raising on H–Pd reaction to its hydrogen response. These experimental results demonstrate that this proposed photothermal effect-assisted reaction temperature enhancement scheme can be used as an effective strategy to improve H–Pd reaction, and it has the great potential to achieve significant performance improvements of hydrogen detection.

Using thermal analysis with kinetic calculation method to assess the thermal stability of azo compound on construction materials

The application of construction polymers in engineering and alternative materials has always occupied a place in the market. In the production process of polymer resins, initiators can be used to lower the polymerization reaction energy threshold, which can improve reaction efficiency and reduce energy loss. However, as a commonly used energetic substance in the polymerization process, azos have caused related process hazards due to their exothermic characteristics. Because of this, it is essential to examine and analyze the thermal hazard characteristics of emerging azo substances, such as 2-cyanopropan-2-imemicarbazide (CABN). Although previous literature performs the calculation on related thermal hazard parameters of CABN, there is still exists a void for discussion in estimating the reaction model to avoid analogous hazards and enhance the existing thermal analysis. Based on the past literature, the reaction model is improved with thermogravimetric analysis as evidence. The revised thermal hazard parameters are calculated as the basis of control and mitigation measures, the kinetic model is used to estimate the modified safety parameters, and in the judgment of the runaway reaction, the critical temperature of the runaway is found by analyzing the influence of slight changes in ambient temperature on the reaction temperature. The results show that the critical temperature that causes CABN to enter the runaway reaction is delayed, and the hazard is lower than in the storage situation. Therefore, the thermal hazard to CABN mainly focuses on the safety environment and measures during storage.

Design of earth‐abundant amorphous transition metal‐based catalysts for electrooxidation of small molecules: Advances and perspectives

AbstractElectrochemical oxidation of small molecules (e.g., water, urea, methanol, hydrazine, and glycerol) has gained growing scientific interest in the fields of electrochemical energy conversion/storage and environmental remediation. Designing cost‐effective catalysts for the electrooxidation of small molecules (ESM) is thus crucial for improving reaction efficiency. Recently, earth‐abundant amorphous transition metal (TM)‐based nanomaterials have aroused souring interest owing to their earth‐abundance, flexible structures, and excellent electrochemical activities. Hundreds of amorphous TM‐based nanomaterials have been designed and used as promising ESM catalysts. Herein, recent advances in the design of amorphous TM‐based ESM catalysts are comprehensively reviewed. The features (e.g., large specific surface area, flexible electronic structure, and facile structure reconstruction) of amorphous TM‐based ESM catalysts are first analyzed. Afterward, the design of various TM‐based catalysts with advanced strategies (e.g., nanostructure design, component regulation, heteroatom doping, and heterostructure construction) is fully scrutinized, and the catalysts’ structure‐performance correlation is emphasized. Future perspectives in the development of cost‐effective amorphous TM‐based catalysts are then outlined. This review is expected to provide practical strategies for the design of next‐generation amorphous electrocatalysts.

A Versatile Integrated Microfluidic Chip Based on Sonic Toothbrush-Assisted Mixing for Analyses of Diverse Biomolecules.

Usually, different assays and instrumentation are required for different types of targets, e.g., nucleic acids, proteins, small molecules, etc., because of significant differences in their structures and sizes. To increase efficiency and reduce costs, a desirable solution is to develop a versatile platform suitable for diverse objectives. Here, we established a versatile detection technique: first, target separation and enrichment were carried out using magnetic beads (MBs); then, different targets were converted to same barcoded DNA strands (BDs) released from gold nanoparticles; finally, sensitive detection of three different targets (miRNA-21, digoxigenin antibody, and aflatoxin B1) was achieved through exonuclease III (Exo III) cyclic cleavage-assisted signal amplification. To simplify the operation, we integrated this technique into a microfluidic chip with multiple chambers in which the requisite reagents were prestored. Just by moving the MBs through different chambers with a magnet, multiple steps can be completed. Due to the limited space in microfluidic chips, the full mixing of MBs and solution is a key point to improve reaction efficiency. The mixing can be achieved by acoustic vibration generated by a small, portable sonic toothbrush. Based on the microfluidic chip, the detection limits of the above three targets were 0.76 pM, 0.16 ng/mL, and 0.56 nM, respectively. Furthermore, miRNA-21 and Digoxigenin antibody (Dig-Ab) in serum and AFB1 in corn powder were also used to demonstrate the performance of this chip. Our versatile platform is easy to operate and is expected to develop into an automatic "sample-to-answer" device.

Enhanced piezo-catalytic H2O2 production over Bi0.5Na0.5TiO3 via piezoelectricity enhancement and surface engineering

The piezo-catalytic hydrogen peroxide (H2O2) production is a promising alternative to traditional anthraquinone oxidation process, but it remains a challenging task. The low conversion efficiency of mechanical energy and the limitedsurface-active sites are the challengings for improving reaction efficiency. Moreover, piezo-catalysts are difficult to prepare in large quantities, limiting the industrial application. To address this issue, this study utilized piezoelectricity enhancement and surface engineering to regulate the Bi0.5Na0.5TiO3 (BNT) for piezo-catalytic H2O2 production. We successfully synthesized an efficient and stable piezo-catalyst, Ag-loaded Bi0.5Na0.5TiO3-AgNbO3 solid solution (Ag/BNT-AN), that was applied to two-channel H2O2 production. The piezo-catalytic activity of Ag/BNT-AN piezo-catalyst was greatly improved through joint regulation of enhancing piezoelectricity by Ag and Nb co-substitution, as well as promoting O2 reduction and H2O oxidation reactions by surface modification with Ag nanoparticals and hydroxyl groups. The optimal Ag/BNT-AN piezo-catalyst displayed H2O2 production rates of 469 µmol g−1 h−1 under ultrasonic vibration, which was 13 times higher than pure BNT. Additionally, the study found that H2O2 could also be synthesized when the catalyst was subjected to simple stirring as mechanical stress, indicating the potential of Ag/BNT-AN to harness low-frequency mechanical energy. This work provides an effective strategy for regulating piezo-catalysts and presents a catalyst design paradigm at the kilogram level.

Selectively Permeable FeOOH Amorphous Layer Coating CdS for Enhancing Photocatalytic Conversion of Benzyl Alcohol and Selectivity to Benzaldehyde.

The development of new strategies to improve reaction efficiency and light utilization is one of the biggest challenges in photosynthetic chemistry. Dynamics control, particularly tuning the adsorption/desorption of reactants and products, is an ideal way to improve the conversion and selectivity in catalytic reactions, but it is rarely studied for photocatalytic organic synthesis. This study concerns the design of an amorphous FeOOH coating to decorate CdS photocatalyst to control the adsorption and desorption of reactants and products to improve reaction efficiency for the photocatalytic conversion of benzyl alcohol (BA) into benzaldehyde (BAD). The best conversion of the core-shell photocatalyst is 74.1 % in 2 h, together with >99.9 % selectivity to BAD, and the photocatalyst exhibits response above 600 nm, which is the longest active wavelength reported for the reaction. Further data illustrate that the amorphous FeOOH coating enables selective sorption of BA/BAD molecules by H-bonding interactions, which may result in the excellent performance. Construction of amorphous coating layers and understanding the selective permeability may provide a new strategy for the design of more efficient photocatalytic systems for organic synthesis.

Plasma-assisted low temperature ammonia decomposition on 3d transition metal (Fe, Co and Ni) doped CeO2 catalysts: Synergetic effect of morphology and co-doping

Catalytic ammonia decomposition generating zero‑carbon and high-energy-density hydrogen over low-cost catalysts has been a hot topic. In this study, ceria support with three morphologies including nanocubes (CeO2-C), nanorods (CeO2-R) and nanospheres (CeO2-S) doped 3d transition metal (Fe, Co and Ni) catalysts have been prepared, characterized and used in ammonia decomposition reaction (ADR). With enhanced metal-support interaction, the co-doped bimetal enriches oxygen vacancies and raised [Ce3+] concentrations, facilitating the electrons transfer from the CeO2 support to active metals. The FeCo/CeO2-S catalyst exhibits excellent thermal stability over continues 48 h. In the non-thermal plasma (NTP) assisted-catalysis in ADR, the FeCo/CeO2-S catalyst showed the highest ammonia conversion with a GHSV of 36,000 mL/gcat/h, which achieves 100% conversion at 550 °C and shows the highest hydrogen generation rate of 29.3 mmol/min·gcat at 500 °C. Our work adopts a novel strategy to improve reaction efficiency of ADR through synergistic promotion of plasma and inexpensive ceria-based catalysts.

Promoting the reduction reactivity of magnetite by introducing trace-K-ions in hydrogen direct reduction

Hydrogen metallurgy exhibits considerable potential for application in the steel industry. However, it is restricted by the low utilization efficiency of hydrogen owing to the poor kinetic conditions and low reduction efficiency, which limit the development of ironmaking via hydrogen direct reduction. Therefore, improving the reduction efficiency of hydrogen direct reduction is critical. In this study, the reactivity of magnetite was considered. The impregnation of trace K+ (0.8 wt%) was found to significantly promote the reduction efficiency, and a possible mechanism was proposed. The increase in the metallization ratio from 88.51% to 99.43% indicated that the 0.8 wt% K+-promoted magnetite exhibited an improved reaction efficiency due to its higher reactivity. Furthermore, modified magnetite reacted under a broader range of gas conditions, e.g., the partial pressure of hydrogen could be reduced to 57%. According to the refined X-ray diffraction patterns, the promotion of the reduction reactivity could mainly be attributed to the increased Fe–O bond polarities, in addition to the solid-state diffusion of O2−, due to the formation of more oxygen vacancies. An enhanced reduction efficiency during hydrogen direct reduction was realized, which could provide promising guidance for the green, sustainable development of hydrogen direct reduction.

N-Chlorosulfonyl carbamate-enabled, photoinduced amidation of quinoxalin-2(1H)-ones.

Reported herein is the design and development of a new photo-induced amidation protocol with the readily available N-chlorosulfonyl carbamate as an effective amidyl-radical precursor, which could be readily prepared from commercial low-cost chlorosulfonyl isocyanate (CSI) and alcohol feedstocks. The synthetic potency of this developed protocol was well demonstrated by direct amidation of various quinoxalin-2(1H)-ones. The protocol could be further streamlined by implementing a one-pot/two-step/three-component process of CSI, alcohol, and quinoxalin-2(1H)-one, with significantly improved reaction efficiency. This methodology offers an intriguing opportunity for rapid expansion of nitrogen-containing molecular complexity, thus inspiring comprehensive exploration of a new reaction mode of CSI reagent.

Sensitive detection of microRNA by dynamic light scattering based on DNAzyme walker-mediated AuNPs self-assembly.

As an important biomarker, microRNAs (miRNAs) play an important role in gene expression, and their detection has attracted increasing attention. In this study, a DNAzyme walker that could provide power to perform autonomous movement was designed. Based on the continuous mechanical motion characteristics of DNAzyme walker, a miRNA detection strategy for the self-assembly of AuNPs induced by the hairpin probe-guided DNAzyme walker "enzyme cleavage and walk" was established. In this strategy, DNAzyme walker continuously cleaved and walked on the hairpin probe on the surface of AuNPs to induce the continuous shedding of some segments of the hairpin probe. The remaining hairpin sequences on the surface of the AuNP pair with each other, causing the nanoparticles to self-assemble. This strategy uses the autonomous movement mechanism of DNAzyme walker to improve reaction efficiency and avoid the problem of using expensive and easily degradable proteases. Secondly, using dynamic light scattering technology as the signal output system, ultra-sensitive detection with a detection limit of 3.6 fM is achieved. In addition, this strategy has been successfully used to analyze target miRNAs in cancer cell samples.

Lactic acid esterification of maize starch in solid state: Assistant effect of pullulanase modification on digestibility and physicochemical properties

The current work was the first report to prepare lactate-esterified debranched starch (LEDS) in solid state mode. Normal maize starch (NS) was initially modified by pullulanase enzyme in granule form and then esterified with lactic acid under dry heating for 3 h at 80 °C and presence of 0.2% w/w sodium hydroxide. Physicochemical properties of the treated starches by single and dual treatments were determined and compared with NS. The enzymatic modification could improve reaction efficiency of esterification process up to 75.2% through partial hydrolysis of starch chains. Compared with NS and individual modifications, the combined treatment significantly increased amylose extent, and the amount of resistant starch (RS) while decreased the freeze thaw stability, viscosity, gelatinization temperatures, paste clarity, swelling power, and relative crystallinity. The morphological examination showed dissociation and degradation of starch granules by single and dual treatments. FT-IR confirmed the introduction of ester groups onto the starch molecules through a band at 1715 cm−1. The impact of designed dual treatment on the environment was assessed by applying Eco-scale index, proving the greenness of the method (score: 75). The findings of this study will provide a theoretical background for development of high RS food products.

Continuous Flow Chemistry Synthesis of Spirocyclic Sultams and Isoquinolines through Rhodium‐Catalyzed C−H Activation.

AbstractIn recent years, continuous flow technology have been applied to C−H activation to improve reaction efficiency. Herein, various imines and alkynes have been smoothly applied to continuous flow system. A series of spirocyclic sultams and isoquinolines can be obtained in excellent yields through [3+2] or [4+2] annulation reactions under relatively mild conditions.

Front Cover: Synthesis of Glycerol Carbonate from Glycerol and CO2 Using CaO as a Dehydrating Agent (Asian J. Org. Chem. 11/2022)

Glycerin, a surplus biomass byproduct of biodiesel production, and CO2, an inexhaustible raw material, was successfully converted into glycerol carbonate, a high value-added chemical, using CaO as a regenerable dehydrating agent in the presence of Zn(OTf)2/1,10-phenanthroline as a catalyst. Mechanical stirring effectively suppresses the solidification of calcium components after dehydration, thereby greatly improving reaction efficiency. Since the carbon atoms of biomass-derived glycerin are derived from CO2 fixed by plant photosynthesis, all carbon atoms of glycerol carbonate stem essentially from CO2. More information can be found in the Research Article by Jun-Chul Choi et al.

Plasmon-Induced Semiconductor-Based Photo-Thermal Catalysis: Fundamentals, Critical Aspects, Design, and Applications

Photo-thermal catalysis is among the most effective alternative pathways used to perform chemical reactions under solar irradiation. The synergistic contributions of heat and light during photo-thermal catalytic processes can effectively improve reaction efficiency and alter design selectivity, even under operational instability. The present review focuses on the recent advances in photo-thermal-driven chemical reactions, basic physics behind the localized surface plasmon resonance (LSPR) formation and enhancement, pathways of charge carrier generation and transfer between plasmonic nanostructures and photo-thermal conversion, critical aspects influencing photo-thermal catalytic performance, tailored symmetry, and morphology engineering used to design efficient photo-thermal catalytic systems. By highlighting the multifield coupling benefits of plasmonic nanomaterials and semiconductor oxides, we summarized and discussed several recently developed photo-thermal catalysts and their catalytic performance in energy production (CO2 conversion and H2 dissociation), environmental protection (VOCs and dyes degradation), and organic compound synthesis (Olefins). Finally, the difficulties and future endeavors related to the design and engineering of photo-thermal catalysts were pointed out to draw the attention of researchers to this sustainable technology used for maximum solar energy utilization.

High-performance microfluidic electrochemical reactor for efficient hydrogen evolution

Hydrogen production from water electrolysis provides an effective bridge between the existing energy system and the layout of green renewable energy. Electrochemical hydrogen gas evolution on the electrode surface will occupy the limited active sites thus significantly increasing the reaction overpotential. It is crucial to study and optimize the bubble behavior on the electrode surface to improve reaction efficiency and lower the energy loss. Herein, a microfluidic electrochemical reactor (MER) has been constructed to optimize the surface gas-liquid two-phase flow behavior during the gas evolution process. The obtained results demonstrate the feasibility of microfluidic design in manipulating the bubble behavior at the electrode interface accompanied with the self-generated gas-liquid two-phase flow, which can directly reduce the overpotentials by facilitating the mass transfer and refreshing catalytic active sites. Compared with conventional H-cell, state-of-the-art efficient and stable performance of hydrogen evolution has been achieved, where the increase in current density was more than 5 times. This work reveals a new strategy for guiding the design of the electrochemical reactor for water splitting.

Study and actual application of the electrochemical reactor in flow-through mode based on channel confinement

The method of enhancing mass transfer and improving reaction efficiency by confinement has attracted much attention in the electrochemical research field. In this research, to make low diffusion-limited electrochemical reactors fieldable, a new electrochemical reactor in flow-through mode was established with the mass-produced Ti/RuO2–IrO2 felt fibers as the electrodes. The effects of voltage, current, and electrode thickness were explored in this study. When the flow mode was switched from flow-by to flow-through, the single-pass degradation effect of rhodamine B rose from 4.4% to 74.8% under the same operating conditions. Meanwhile, a mass transfer model was established based on the results of removal efficiency and electrode channel parameters. The model was in good agreement with the new electrode parameters verification (R2 > 0.970). With this model, it could derive specific results on the effect of pore size change on the treatment effect. The impact of enhancing mass transfer by confining the pore sizes is most clearly gained at a certain range (less than 100 μm). Furthermore, a pilot-scale electrochemical reactor in flow-through mode was built, and excellent performance was shown in the treatment of actual waste leachate. The removal efficiencies of total nitrogen, ammonia, and nitrate were 80.9%, 88.6%, and 64.5% in 30 min, respectively. It will be a promising technology with good prospect.

Preparation of Janus nanosheets composed of gold/palladium nanoparticles and reduced graphene oxide for highly efficient emulsion catalysis

Interface/emulsion catalysis is an effective approach for many organic and inorganic chemical reactions. Positioning catalysts at the interface is essential for highly efficient interface/emulsion catalysis. The sheet-like Janus nanostructures may have great advantages in stabilizing emulsions and improving reaction efficiency. In this work, by using a simple emulsion reaction and photodeposition, we successfully prepare the Janus nanosheets with opposite sides composed of AuNPs/PdNPs and reduced graphene oxide (rGO) respectively, referred to as AuNP-rGO/PdNP-rGO Janus nanosheets. Due to the distinct hydrophilicities on opposite sides, the prepared Janus nanosheets demonstrate high efficiency in emulsion stabilization and emulsion catalysis. By introducing the prepared PdNP-rGO and AuNP-rGO Janus nanosheets in emulsion reactions, highly efficient hydrogenation of p-nitroanisole and photocatalytic degradation of Nile red are demonstrated. This work provides a simple and cost-effective method to prepare Janus nanosheets and realize highly efficient emulsion reactions, and this strategy can be extended to promote many other interface/emulsion reactions.