Catalytic System Research Articles

Removal of tetracycline antibiotic from aqueous solution using bimetallic CuCo-ZIFs as an efficient catalyst in the presence of hydrogen peroxide

Antibiotics play an important role in disease treatment; however, they are also a threat to public health and the ecosystem. Therefore, a bimetallic CuCo-ZIFs catalyst was manufactured through the ultrasonic-assisted solvothermal method to activate H2O2 towards the removal of tetracycline (TC) in an aqueous environment, a polluting broad-spectrum antibiotic model. PXRD, SEM, TEM, EDX, TGA, FT-IR, and BET analyses indicated that CuCo-ZIFs cubic crystals were successfully synthesized with high crystallinity, large specific surface area, and ideal thermal stability. Factors affecting the TC removal were investigated, including CuCo-ZIFs dosage, H2O2 concentration, treatment time, initial TC concentration, and reaction temperature. The results showed that the CuCo-ZIFs/H2O2 catalytic system was capable of effectively handling TC, with about 93.9% of TC removed in the presence of 0.3 g.L-1 CuCo-ZIFs, 0.01 mol.L-1 H2O2 at room temperature within 30 min. Conclusively, this study contributes to expanding the application potential of bimetallic CuCo-ZIFs materials to eliminate antibiotic residues in an aqueous environment and inspire research on environmental improvement.

Homogeneous Catalysts of RedOx Processes Based on Heteropolyacid Solutions. VI: Developing a Process for Low-Temperature Oxidation of CO with Oxygen

Research on the development of a homogeneous process for low-temperature oxidation of carbon monoxide in the presence of a “platinum group metal + vanadium-containing heteropolyacid (HPA)” catalytic system has been presented. The optimal reaction conditions, ensuring the maximum rate of CO oxidation to CO2, have been determined; for this reaction the kinetic features have been established, and its mechanism has been proposed. It has been shown that homogeneous systems based on PdII complex exhibit high activity and productivity, but have low stability and operate only at pH below 1,5. The stability of the catalyst can be increased by simultaneous introduction of σ- and π-donor ligands into the system; however, it is more effective to use the PtIV complex in the presence of catalytic amounts of palladium salt at a ratio of 100/1. The transition from HPA solutions with a low content of vanadium atoms (H7PMo8V4O40) to solutions of modified compositions (H10P3Mo18V7O84) ensures an increase in the activity and productivity of the system, with the kinetics of CO oxidation being maintained. The combined homogeneous catalyst PtIV + PdII + H10P3Mo18V7O84 remains stable during multi-cycle use without reducing activity, operates without an induction period and can be used at pH range of 1,7–2,0, which simplifies the process equipment.

Ligand-Free Iron-Catalyzed Carbonylation of Aryl Iodides with Alkenyl Boronic Acids: Access to α,β-Unsaturated Ketones.

The application of earth-abundant and low-toxicity iron catalysts as replacements for palladium in carbonylative coupling reactions remains challenging and largely unexplored. Reported here is a highly efficient iron-catalyzed carbonylation of aryl iodides with alkenyl boronic acids under ligand-free conditions, enabling the synthesis of α,β-unsaturated ketones even at atmospheric CO pressure. The broad applicability, including its effectiveness with α-branched enones and biologically active molecules, along with high yields and selectivity, underlines the general applicability of this catalytic system.

Selective Hydroboration of C−C Single Bonds without Transition‐Metal Catalysis

AbstractSelective hydroboration of C−C single bonds presents a fundamental challenge in the chemical industry. Previously, only catalytic systems utilizing precious metals Ir and Rh, in conjunction with N‐ and P‐ ligands, could achieve this, ensuring bond cleavage and selectivity. In sharp contrast, we discovered an unprecedented and general transition‐metal‐free system for the hydroboration of C−C single bonds. This methodology is transition‐metal and ligand‐free and surpasses the transition‐metal systems regarding chemo‐ and regioselectivities, substrate versatility, or yields. In addition, our system tolerates various functional groups such as Ar−X (X=halides), heterocyclic rings, ketones, esters, amides, nitro, nitriles, and C=C double bonds, which are typically susceptible to hydroboration in the presence of transition metals. As a result, a diverse range of γ‐boronated amines with varied structures and functions has been readily obtained. Experimental mechanistic studies, density functional theory (DFT), and intrinsic bond orbital (IBO) calculations unveiled a hydroborane‐promoted C−C bond cleavage and hydride‐shift reaction pathway. The carbonyl group of the amide suppresses dehydrogenation between the free N−H and hydroborane. The lone pair on the nitrogen of the amide facilitates the cleavage of C−C bonds in cyclopropanes.

Oxidative degradation of chitosan by Fe-MCM-41 heterogeneous Fenton-like system

We herein disclosed an efficient multiphase Fenton-like catalytic system for oxidative degradation of chitosan. By utilizing Fe-MCM-41, featured with regular mesoporous structure and high specific surface area, the activation efficiency of H2O2 was significantly enhanced and the chitosan degradation efficiency proved by 28.1% higher than the conventional system using H2O2 alone. Under optimized conditions (5 g/L chitosan, 0.5 g/L Fe-MCM-41, 0.16 mol/L CH3COOH, 0.86 mol/L H2O2, 50 °C, 140 min), the viscosity reduction rate of chitosan reached an impressive 98.2%. Among the catalysts tested, Fe-MCM-41 with a loading factor of x = 0.12 demonstrated optimal degradation performance. After four recycles, the degradation efficiency maintained > 93.6%, demonstrating its excellent stability and recyclability for potential industrial applications. Kinetic studies provided further elucidation of the reaction mechanism, which indicated that the degradation process of chitosan followed a first-order kinetic model, with an apparent activation energy (Ea) of 48.91 kJ/mol. This novel and efficient strategy for chitosan degradation, addressed the challenges of catalyst recovery and secondary pollution typically associated with traditional Fenton systems, and posed broad application potential for polysaccharide material processing.

Epoxidation of Chalcone Derivatives under Visible-Light Irradiation: An Organophotoredox Catalytic Approach

AbstractEpoxidation of α,β-unsaturated ketones under visible-light irradiation constitutes a significant chemical transformation with potential applications in the synthesis of epoxypropane derivatives. An organophotoredox catalytic system is herein reported to facilitate efficient aerobic epoxidation. This protocol enables the conversion of α,β-unsaturated ketones into their corresponding epoxy products with moderate to high yields under benign reaction conditions. The methodology demonstrates broad functional-group compatibility, providing a reliable and direct route to a variety of functionalized epoxypropane compounds. Additionally, the absence of heavy metals in this strategy renders it particularly suitable for the pharmaceutical industry, offering a new avenue for the synthesis of epichlorohydrin drugs.

Synthesis of furan-2-ones and spiro[furan-2,3ʹ-indoline] derivatives using polyether sulfone sulfamic acid catalysis

Polyether sulfone sulfamic acid (PES-NHSO3H) was prepared by simple sulfonation of a modified polyether sulfone. The number of acidic sites (SO3H) was determined to be 4.23 mmol H+/g by acid-base titration and 4.29 mmol H+/g by barium sulfate test. PES-NHSO3H was used as an efficient acidic catalytic system for the preparation of functionalized furan-2-ones and 2ʹ,5-dioxo-5 H-spiro[furan-2,3 ʹ -indoline]-3-carboxylate derivatives via the three-component reaction of anilines, aldehydes/1-ethylindoline-2,3-dione, and diethyl acetylene dicarboxylate in high yields (85–97%). The effect of polar and non-polar solvents on the productivity of the reaction was investigated. The catalyst was recovered 11 times without losses in catalytic potential.

Photocatalytic Synthesis of Glycine from Methanol and Nitrate

AbstractPhotocatalytic utilization of methanol and nitrate as carbon and nitrogen sources for the direct synthesis of amino acids could provide a sustainable way for the valorization of green “liquid sunlight” and nitrate waste. In this study, we develop an efficient photochemical method to synthesize glycine directly from methanol and nitrate, which cascades the C−C coupling to form glycol, nitrate reduction to NH3, and finally C−N coupling to generate glycine. Interestingly, the involved photocatalytic tandem reactions show a synergistic effect, in which the presence of nitrate is the dominant factor to enable the overall reaction and reach high synthetic efficiency. Ba2+−TiO2 nanoparticles are confirmed as a feasible and efficient catalyst system for the photosynthesis of glycine with a remarkable glycine photosynthesis rate of 870 μmol gcat−1 h−1 under optimal conditions. This work establishes a novel catalytic system for amino acid synthesis from methanol and nitrate under mild conditions. These results also allow us to further suppose the formation pathways of amino acids on the primitive earth, as an extension to proposals based on the Miller‐Urey experiments.

Oxidative Aromatization of Ethane

This study is focused on examining the incorporation of oxidative dehydrogenation into the aromatization of ethane, utilizing thermodynamic analysis and catalytic experiments. The catalysts were characterized by inverse temperature programmed reduction, X‐ray photoelectron spectroscopy (XPS) and X‐ray diffraction (XRD). The results indicated that a blend of the M1 catalyst, containing oxides of vanadium, niobium, and tellurium, with H‐ZSM‐5, serves as an effective catalyst system for the oxidative aromatization of ethane at T = 380 °C. The M1's role in the oxidative dehydrogenation of ethane contributes to de‐bottlenecking the essential step of the reaction. On the zeolitic catalyst aromatic compounds are formed from a surface hydrocarbon pool. In parallel, the oxidation of these intermediates was observed. Also, the formation of paraffins through H‐transfer was evident from the catalytic results. While the zeolite underwent significant deactivation due to coking, the M1 catalyst demonstrated highly stable activity. Interestingly, the system did not show any synergistic effects. Based on the structure‐activity relation of the catalytic system a reaction mechanism is proposed.

Key Ingredients for the Modeling of Single‐Atom Electrocatalysts

AbstractSingle‐atom catalysis is gaining interest also because of its potential applications in a broad spectrum of electrochemical reactions. The reactivity of single‐atom catalysts (SACs) is typically modeled with first principles approaches taking insight from heterogenous catalysis. An increasing number of studies show that the chemistry of SACs is more complex than often assumed, and shares many aspects in common with coordination chemistry. This evidence raises challenges for computational electrocatalysis of SACs. In this perspective we highlight a few fundamental ingredients that one need to consider to provide reliable predictions on the reactivity of SACs for electrochemical applications. We discuss the role of the local coordination of the metal active phase, the need to use self‐interaction corrected functionals, in particular when systems have magnetic ground states. We highlight the formation of unconventional intermediates with respect to classical metal electrodes, the need to include the stability of SACs in electrochemical conditions and the role of solvation in the analysis of new potential catalytic systems. This brief account can be considered as a tutorial underlining the importance of treating the reactivity of SACs. In fact, neglecting some of these aspects could lead to unreliable predictions failing in the design of new electrocatalysts.

Preparation and NH3 adsorption behavior of porous magnesium oxychloride cement-based SrCl2

In addressing challenges in Selective Catalytic Reduction (SCR) systems in vehicles, the development of novel SrCl2 composite materials with high ammonia adsorption and structural stability is crucial. In this context, we employed the porous magnesium oxychloride cement (PMOC) as a carrier material, successfully fabricating a mesoporous PMOC-SrCl2 material via solution impregnation technology. Simultaneously, we employed various characterization techniques such as XRD, full-pore analysis, TG, SEM, TEM, and EDS to examine the material. We conducted static adsorption assessments on numerous candidate materials at 0.1Mpa and 293.15 K. The synthesized C3 series material (Mass ratio of SrCl2 to PMOC = 10:3), solution impregnated for 1 h, exhibited exceptional ammonia adsorption capacity (up to 38.01 mmol·g−1). Through model fitting of experimental data, we discovered that the adsorption process of this material closely aligns with the pseudo-second-order kinetic model and the Langmuir model. Over an adsorption time span of 180 min, the adsorption rate of the composite material increased by 129 % compared to pure SrCl2. In the cycle performance testing phase, we observed that the material exhibited no significant degradation in performance after undergoing 10 cycles of adsorption/desorption. This structurally stable, cost-effective, and readily accessible high-efficiency ammonia adsorption material undoubtedly possesses immense potential to solve the application challenges of ammonia adsorption materials within automotive selective catalytic reduction systems.

Recent Progress on Cobalt‐Based Heterogeneous Catalysts for Hydrogen Production from Ammonia Borane

AbstractAmmonia borane (NH3BH3, AB) is a quintessential exemplar of chemical hydrogen storage materials and has been widely used in hydrogen evolution. Although expensive metal catalysts (such as Rh, Ru, Pt, Ag, etc.) exhibit high activity in the hydrolysis of ammonia borane, inexpensive metals are more economical. Cobalt (Co), in particular, is not only relatively inexpensive and readily available, but also possesses high activity and selectivity. Compared to other catalysts, cobalt‐based catalysts have better durability and can maintain catalytic activity for a longer period of time, making them favored by researchers. These catalysts demonstrate excellent stability, hydrogen evolution rate, and turn over frequency. This article summarized previous progress in low price metal cobalt‐based catalysts for hydrogen precipitation from ammonia borane, focusing on cobalt‐based catalysts supported on various supports, especially those supported on carbon materials, metal oxides, MOFs, and nickel foams. The characteristics of high‐performance catalytic systems are analyzed in detail. The development prospects of Co catalysts for hydrogen production from ammonia borane were also discussed. In summary, this review compiles various supported and other types of cobalt based catalysts in recent years, and also identifies the existing problems with these catalysts, providing a reference for developers to study these catalysts. It is believed that through careful regulation of the electronic and spatial structures of Co based catalysts, well‐designed Co based non precious metal catalysts will play a significant role in the decomposition of ammonia borane.

On‐Purpose Production of Light Olefins Through Oxidative Dehydrogenation: An Overview of Recent Developments

AbstractProducts made from light olefins play an important role in our daily lives. Traditional light olefins production based on steam cracking and fluid catalytic cracking suffer from high energy consumption and CO2 emissions. Thereby, the continually increasing demand for light olefins needs to be met through more environmentally sustainable procedures. On‐purpose production routes are preferred choice among petrochemicals manufacturers, being energy efficient and having lower carbon footprint. Among them, oxidative dehydrogenation (ODH) of light paraffins is a thermodynamically favourable exothermic process as compared to non‐oxidative routes. They can be operated at lower temperatures and have propensity of low coke deposition on catalyst, thereby resisting rapid catalyst deactivation. Herein, we have analysed various catalytic systems utilised in the oxidative dehydrogenation process. We have reviewed role of support, chemical composition of catalyst, presence of dopant, oxidation state of active metal, controlled surface modification by oxidative and reductive pretreatments, and reaction factors for each system. The performance of various catalytic systems for ODH of ethane, propane and butane in the presence of O2, CO2, N2O and special oxidants have been reviewed. A short critical overview on emerging on‐purpose routes for the production of renewable 1,3 butadiene has also been discussed.

Enhancement of H2-water mass transfer using methyl-modified hollow mesoporous silica nanoparticles for efficient microbial CO2 reduction

Inorganic-microbial hybrid catalysis is an emerging technology that uses electrical energy to drive microorganisms to reduce CO2 into high value-added compounds, and it has broad application prospects in CO2 reduction. However, the low current density (production yield) limits its practical application. Hydrogen-mediated inorganic-microbial hybrid catalysis system can achieve higher current density, but it is limited by low H2 mass transfer. Here, silica nanoparticles were used to enhance the hydrogen mass transfer for highly efficient CO2 reduction. Solid silica (SN), mesoporous silica (MSN), hollow mesoporous silica (HMSN), and methyl-modified hollow mesoporous silica (MHMSN) were firstly prepared and tested for the enhancement of hydrogen mass transfer. Of these, MHMSN nanoparticles at a concentration of 0.3 wt% were the best at enhancing gas-liquid mass transfer, the volumetric mass transfer coefficient (KLa) and saturated dissolved hydrogen concentration of H2 are 0.53 min-1 and 1.81 mg l-1, respectively. Compared with the control group without added nanoparticles, MHMSN significantly increased the solubility and KLa of H2. This can be attributed that the addition of MHMSN promoted the detached process of hydrogen bubbles from the electrode surface, which made the diameter of hydrogen bubbles smaller, increased the gas-liquid mass transfer area, and strengthened the mass transfer process of H2. Furthermore, it was added to the inorganic-microbial hybrid catalysis system to effectively promote the microbial carbon reduction process, achieving a polyhydroxybutyrate (PHB) yield of up to 700 mg l-1, and the electron utilization rate and CO2 conversion rate were 51 % and 58 % higher than the control group, respectively. These results demonstrated that the addition of MHMSN is an effective approach to enhancing the performance of H2-mediated inorganic-microbial hybrid catalysis system.

Development of an efficient biocatalytic three-component reaction for synthesizing pyrrole derivatives

Multi-component reactions (MCRs) enable the development of efficient and atom-economic methods for synthesizing pyrrole derivatives. However, the current MCRs methods for synthesizing pyrrole derivatives in the enzymatic process have been unexploited. Herein, we developed a one-pot three-component enzymatic promiscuous catalytic system with green, efficient, and atom-economic to construct pyrrole derivatives. In this system, amines and 1,3-dicarbonyl compounds formed enamines with subsequent Michael addition with nitroolefins catalyzed by trypsin. A series of pyrrole derivatives were successfully obtained with moderate to good yield (up to 92 %). In addition, molecular simulations were conducted to gain insight into the source of differing tolerance of aromatic amides and fatty amines and the intrinsic effect of solvents in this system. This enzymatic catalytic one-pot three-component system has excellent functional tolerance, simple operation, and application potential for industrial production demonstrated by the gram scale experiment.

Advancements in Primary Alcohol Oxidation Leading to Carboxylic Acids: A Detailed Review

This review article explores the direct oxidation of primary alcohols into carboxylic acids, highlighting its importance in organic synthesis for producing valuable chemicals in a sustainable and efficient manner. Carboxylic acids are widely employed in a wide range of applications, encompassing food preservatives, insecticides, dye intermediates, coatings, plasticizers, spices, flavors, scents, and a variety of industries such as polymers, solvents, and medications. This review article covers recent advancements in catalytic systems, including catalysts based on transition metals, organocatalysts, nanocatalysts, and electrochemical methods. It examines the impact of reaction conditions such as solvents, temperature, and substrate scope on these processes. The review also delves into mechanistic insights and recent developments in tandem and cascade reactions, aiming to provide a comprehensive understanding of current strategies and future research directions in this field.

Boosting Electrocatalytic Performance of Sulfide Oxidation on Polyoxomolybdates with Synergistic Effects of CNT‐Doped Aerogel Foams

AbstractThe meticulous design of highly efficient indirect electrocatalysts with value‐added conversion properties remains a substantial challenge within the realm of organic catalysis. While polyoxometalates (POMs) serve as crucial active centers in catalytic modeling systems for chemical materials, their exploration in electrocatalytic organic molecular transformations is hindered by kinetic barriers. Therefore, an efficient protocol is established for the synthesis of electrocatalysts utilizing polyoxomolybdates (CuMo6) immobilized on aerogel foams (CMC). The electrical conductivity and electrocatalytic activities of the electrocatalyst (CuMo6/CNT@CMC) can be readily enhanced by adjusting the microenvironment between the CuMo6 and CMC using carbon nanotubes (CNT). Controlled experiments demonstrate that the CuMo6/CNT@CMC electrocatalyst for the oxidation of sulfide achieves an impressive Faradaic Efficiency (FE) exceeding 95% under ambient conditions, while the working potential is markedly lower than that of reported heterogeneous electrocatalysts. Combined experimental and theoretical analyses suggest that the modulated electronic synergistic interaction between the Cu‐assisted Mo sites and CNT within foam favors the appropriate binding of PhCH3S+• intermediates, thereby promoting the selective oxidation of sulfides. This study paves the way for the utilization of polyoxometalate‐based materials with simple synthesis methods for various electrocatalytic applications.

Stable and Recyclable Copper Nanoclusters with Exposed Active Sites for Broad‐Scope Protosilylation in Open Air

Despite recent advances in cluster‐based catalysis for organic synthesis, the substrate scope of reactions catalyzed by metal nanoclusters is typically not superior to previously established catalytic systems. Herein, we develop new atomically precise copper nanoclusters for protosilylation, with scope expanding to alkenes and simple enynes that were not suitable for prior synthetic methodologies with traditional copper complexes. The involvement of a second copper center in the metal kernel during the migratory insertion step is thought to be responsible for the expanded scope. In addition, the reaction is highly compatible with water and can be carried out in open air rather than under inert gas protection. Mechanistic studies suggest that the cluster‐catalyzed protosilylation proceeds in the absence of silyl radicals. The current findings demonstrate the potential of using metal nanoclusters for practical and sustainable chemical synthesis.

Stable and Recyclable Copper Nanoclusters with Exposed Active Sites for Broad-Scope Protosilylation in Open Air.

Despite recent advances in cluster-based catalysis for organic synthesis, the substrate scope of reactions catalyzed by metal nanoclusters is typically not superior to previously established catalytic systems. Herein, we develop new atomically precise copper nanoclusters for protosilylation, with scope expanding to alkenes and simple enynes that were not suitable for prior synthetic methodologies with traditional copper complexes. The involvement of a second copper center in the metal kernel during the migratory insertion step is thought to be responsible for the expanded scope. In addition, the reaction is highly compatible with water and can be carried out in open air rather than under inert gas protection. Mechanistic studies suggest that the cluster-catalyzed protosilylation proceeds in the absence of silyl radicals. The current findings demonstrate the potential of using metal nanoclusters for practical and sustainable chemical synthesis.

Base-free aqueous Suzuki–Miyaura coupling reaction using recoverable bi-functional Pd supported nanocatalyst

A solid base catalyst comprising pyridine-palladium polyorganosiloxane framework was synthesized via a grafting method. The resulting organic–inorganic hybrid palladium nanomaterial was characterized by 13C CP-MAS NMR, 29Si CP-MAS NMR, XRD, EDX, TEM, TGA, and the BET measurements. The hybrid palladium nanomaterial exhibited high catalytic activity for the Suzuki–Miyaura cross-coupling reaction between aryl chlorides and phenylboronic acid under base-free and aerobic conditions. A maximum turnover number (TON) of 3150, with a 0.2 mol% Pd loading and a reaction temperature of 80 °C in aqueous solution. The catalyst demonstrated remarkable stability, maintaining its activity even after six cycles of reuse without significant loss of activity. TEM images showed that the catalyst retained its structure and high-order mesostructure after several uses. ICP-AES also confirmed the absence of palladium contamination in the final products. Leaching test studies further confirmed the true heterogeneous nature of the developed catalytic system.