Efficient Catalytic System Research Articles

Recyclable and convenient-to-handle Pt/ethylene glycol catalytic system – an approach to sustainable hydrosilylation

This study presents a highly efficient and simple recyclable catalytic system for heterophase hydrosilylation. This catalytic system consisting of a commercially available platinum precatalyst, namely K2PtCl4, and a cheap green solvent, namely ethylene glycol (EG), is easily prepared by dissolving K2PtCl4 in EG without employing ligands, additives, or inert atmosphere, at r.t. It was found that mononuclear Pt0-complex generated in the catalytic system is a single-atom catalyst. The method enables 36 recycles with quantitative yield in air at r.t. The reaction proceeds at a high rate even with small catalyst loadings. High values of TON (up to 105) and TOF (up to 106) were achieved. This approach is applicable to a wide range of unsaturated compounds, such as terminal or internal alkenes, alkynes, and alkyl-, phenyl-, and siloxy-containing hydrosilanes. Moreover, the heterophase catalytic system is suitable for synthesis of linear and cross-linked polyorganosiloxanes. In most cases, the reaction provides high yields (up to 95–99%) and selectivity. It gives mostly anti-Markovnikov products, which can be isolated from the catalytic system by simple decantation. The process is scalable to gram quantities.

Synthesis, Characterization and Photoactivation Studies on the Novel Pt(IV)-Based [Pt(OCOCH3)3(phterpy)] Complex.

Photoactivatable Pt(IV) prodrugs represent nowadays an intriguing class of potential metal-based drugs, endowed with more chemical inertness in their oxidized form and better selectivity for the target with respect to the clinically established Pt(II) compounds. In fact, they have the possibility to be reduced by light irradiation directly at the site of interest. For this reason, we synthesized a new Pt(IV) complex, [Pt(OCOCH3)3(4'-phenyl-2,2':6',2''-terpyridine)][CF3SO3] (1), that is well soluble in aqueous medium and totally unreactive towards selected model biomolecules until its reduction. The highlight of this work is the rapid and efficient photoreduction of 1 with visible light (460 nm), which leads to its reactive Pt(II) analogue. This behavior was made possible by taking advantage of an efficient catalytic system based on flavin and NADH, which is naturally present in the cellular environment. As a comparison, the reduction of 1 was also studied with simple UV irradiation, but both UV-Vis spectrophotometry and 1H-NMR spectrometry showed that the flavin-catalyzed reduction with visible light was faster. Lastly, the reactivity against two representative biological targets, i.e., human serum albumin and one monofilament oligonucleotide fragment, was evaluated by high-resolution mass spectrometry. The results clearly pointed out that the prodrug 1 did not interact with these targets until its photoreduction to the Pt(II) analogue.

Polyoxometalate-based graphitic carbon nitride for reduction of toxic nitro aromatic compounds in water

The present study focuses on the development of an impressive way to eliminate toxic nitro aromatic compounds as hazardous industrial pollutants using polyoxometalate-based composites. For this purpose, transition metal substituted Keggin-type polyoxometalates were integrated on modified protonated graphitic carbon nitride (POMs@g-C3N4) via an electrostatic self-assembly strategy. These stable compounds are characterized by different techniques and used in the reduction of toxic nitro aromatic compounds. Among Cr, Mn, Fe, Co, Ni, Cu, and Zn, the composite containing copper substituted Keggin-type polyoxometalate (CuPOM@g-C3N4) presents the most respectable catalytic activity in these reduction reactions. Moreover, this efficient catalytic system is applied in the reduction of different toxic nitro aromatic compounds into the amino aromatic analogues with appropriate conversions and reaction times. Kinetic studies are also used to determine their apparent rate constants. This process is easy, low-cost, non-toxic, high potential catalytic performance, and environmental friendliness that could be accomplished in water as solvent and at room temperature.

Graphene-Based Derivatives Heterostructured Catalytic Systems for Sustainable Hydrogen Energy via Overall Water Splitting

The global climate crisis has cultivated the demand for sustainable energy resources as fossil derivative fuels are functional in catalyzing the rate of environmental breakdown. Sustainable energy solutions generate various renewable energy prospects capable of delivering efficient energy operations. Among these prospects, green H2 energy generated via overall water splitting is an effective approach towards sustainability ascribed to the higher gravimetric density and efficiency of H2 fuel. In this review, we sought to discuss the applicability and challenges of graphene-based derivatives in H2 evolution operations through photochemical, electrochemical and photoelectrochemical water-splitting pathways. The unique layered structure of graphene-based derivatives alongside marvelous optoelectronic and physicochemical properties ease out the thermodynamic uphill of water splitting better than their non-layered counterparts. In addition, the heterojunction formation in the graphene derivatives with visible light catalysts propels the kinetics of HER. Functionalized GO and rGO derivatives of graphene are riveting catalysts that have received extensive interest from researchers attributed to their accelerated chemical and mechanical stability, tunable band structure and larger surface area, providing more exposed active sites for HER. The surface organic functional groups of GO/rGO assist in establishing synergetic interfacial contact with other catalysts. Thus, these groups provide structural and chemical versatility to GO/rGO-based heterostructured catalysts, which effectively improve their physicochemical parameters that drive their catalytic performance towards HER. In order to develop a cost-effective and highly efficient catalytic system, graphene-based derivatives are promising heterostructured catalysts that exhibit a good relationship between catalytic efficiency and robustness.

Oxygen-functionalized Ti3C2 MXene/exfoliated montmorillonite supported S-scheme BiOBr/Bi2MoO6 heterostructures for efficient photocatalytic quinolone antibiotics degradation

Exploiting an excellent photocatalyst system with sufficient photogenerated charge separation and strong redox ability for efficient degradation of multiple fluoroquinolones (FQs) antibiotics was crucial but still a big challenge. The significant impacts of novel oxygen-functionalized Ti3C2 MXene/exfoliated montmorillonite (Ti3C2/MMTex) severed as a superior co-catalyst to boost the catalytic activity of single semiconductor was verified in our previous work. Based on that, the Bi2MoO6 particles/BiOBr nanosheets were ingeniously anchored onto multilayer O-functionalized Ti3C2/MMTex by the form of in-situ self-assembly via facile two-step microwave-assisted solvothermal process. Representative characterizations confirmed that Ti3C2/MMTex exhibited chemical stability and achieved transformation from surface F-terminal to O-terminal owing to the introduction of MMTex. Moreover, Ti3C2/MMTex supporter greatly decreased the accumulation and improved the morphology of Bi2MoO6/BiOBr S-scheme heterojunction. With extensive Bi2MoO6/BiOBr sheets embedding onto Ti3C2/MMTex, the quaternary BiOBr/Bi2MoO6/Ti3C2/MMTex catalyst displayed extraordinary coral reef-like structure, followed by abundantly exposing high-active {001} facets of BiOBr. Furthermore, owing to the Schottky/S-scheme double heterojunction linkage system, the multiple electrons transfer pathways formed over the quaternary composite effectively facilitated the separation of photogenerated charge carriers, thereby leading to the enhanced generation of •O2− and •OH. Hence, multiple FQs antibiotics degradation efficiency over BiOBr/Bi2MoO6/Ti3C2/MMTex all up to 90%, especially for levofloxacin (LEV), 99% LEV could be eliminated within 120 min. Besides, superior recyclability and stability were revealed in this quaternary composite. Notably, demethylation and piperazine ring-opening dominated LEV degradation pathway and the generated intermediates possessed lower toxicity and ecological risks. Our study further excavates multiple positive effects of Ti3C2/MMTex co-catalyst in constructing the efficient catalytic system, and supplies novelty tactics to engineer a stable non-noble meta/Bi-based semiconductor Schottky/S-scheme double heterojunction linkage system with compact interface contact.

Affinity of K+to organic matter promotes reactions: degradation of super stable phenolic epoxy vinyl ester resin to value-added chemicals

An efficient catalytic system was developed to cleave the ester bond of highly stable waste thermoset phenolic epoxy vinyl ester resin and recover value-added chemicals.

Additive-free reductive hydrodeoxygenation of fatty acids catalyzed by inexpensive simple nickel(ii) compounds

Using Ni(AcO)2·4H2O as a catalytic precursor and PhSiH3, a simple and efficient catalytic system was synthesized for reducing FAs with high conversion under relatively mild conditions.

Novel Cu(ii) acidic deep eutectic solvent as an efficient and green multifunctional catalytic solvent system in base-free conditions to synthesize 1,4-disubstituted 1,2,3-triazoles

A novel Cu(ii)-acidic deep eutectic solvent was synthesized by the eco-friendly strategy and applied as multifunctional catalytic solvent system to furnish high yield of 1,2,3-triazoles in reducing agent- and base-free condition via CuAAC reaction.

Promoting the production of 5-hydroxymethylfurfural from high-concentration fructose by creating micro-reactors in a mixed solvent

An efficient catalytic system for producing 5-hydroxymethylfurfural from high-concentration fructose has been built by creating micro-reactors with cetyltrimethylammonium bromide in a mixed solvent of 1,4-dioxane and water.

Highly efficient α-arylation of aryl ketones with aryl chlorides by using bulky imidazolylidene-ligated oxazoline palladacycles.

α-Aryl derivatives of carbonyl compounds are important building blocks. Herein, we presented an efficient catalytic system for the α-arylation of aryl ketones with inactive aryl chlorides by firstly using N,N'-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr)-ligated chiral oxazoline palladacycles, and tolerated a wide range of substrates at low catalyst loadings, leading to the desired products in good to excellent yields.

Synthesis of biofuel precursors from benzaldehyde and cyclopentanone via aldehyde-ketone condensation in a deep eutectic solvent system.

Production of biofuel precursors from biomass-derived platform compounds (BDPC) has a profound influence on biofuel industries. Herein, an efficient catalytic system composed of the deep eutectic solvent (DES, i.e., ChCl/Fa) and SnCl4 (ChCl/Fa-SnCl4) was developed to produce biofuel precursors (C12 and C19) through aldehyde-ketone (A-K) condensation of benzaldehyde (BD) and cyclopentanone (CPO). ChCl/Fa-SnCl4 exhibited the prospective catalytic performance and given the high selectivity (SC12 = 49.20%, SC19 = 15.20%) and total yield (YC12+C19 = 64.37%) of C12 and C19, as well as 99.96% BD conversion under the optimized conditions (BD : CPO molar ratio of 1 : 6, ChCl : Fa molar ratio of 1 : 12, 4 mmol SnCl4, 80 °C for 120 min). Subsequently, the C12 and C19 precursors were successfully applied to generate cyclic alkanes (C12H14 and C19H18) by hydrodeoxygenation with selectivity of 37.61% and 24.10%, respectively. Finally, the potential catalytic mechanism was explored by density functional theory (DFT) calculations. The results unveiled that the formation of a stable structure for the ChCl/Fa-SnCl4 system was ascribed to the viable interactions among ChCl, Fa and SnCl4 by coordination bonds, electrostatic interactions and H-bonds, which decreased reaction energy barriers and drove the condensation of BD and CPO. In this case, the catalytic reactions between BD and CPO were enhanced to promote the synthesis of C12 and C19. This work provides a novel strategy for the applicability of different BDPC to synthesize fuel precursors for the development of liquid biofuels.

Biphenyl aldehyde-based ternary catalytic system catalyzed Tsuji–Trost allylation of N-unprotected amino acid esters

A highly efficient biphenyl aldehyde-based ternary catalytic system is rationally designed and applied in the direct α-allylation reaction of N-unprotected amino acid esters and allyl alcohol acetates. The chemoselectivity of C-allylation and N-allylation is efficiently controlled and various racemic α,α-disubstituted amino acid esters are generated in good-to-high yields. The target products can be readily converted into structurally diverse α,α-disubstituted amino acids at a gram scale.

A Convenient, Efficient, and Inexpensive Copper(I) Complex Catalyzed Sonogashira Cross-Coupling of o-Iodoanilines with Terminal Alkynes

AbstractUsing (PPh3)2CuBH4 as catalyst, a convenient, efficient, and inexpensive palladium-free catalytic system has been developed to catalyze Sonogashira cross-coupling of o-iodoanilines with terminal alkynes under an air atmosphere to give a range of 2-ethynylaniline derivatives with up to 99% yield. This protocol is amenable to scale up. Notable features of the approach include good functional group tolerance, air atmosphere, and excellent yields.

Magnetically Induced CO2 Methanation In Continuous Flow Over Supported Nickel Catalysts with Improved Energy Efficiency.

A new selective and efficient catalytic system for magnetically induced catalytic CO2 methanation was developed, composed of an abundant iron-based heating agent, namely a commercial iron wool, combined with supported Nickel nanoparticles (Ni NPs) as catalysts. The effect of metal oxide support was evaluated by preparing different 10 wt % Ni catalyst (TiO2 , ZrO2 , CeO2 , and CeZrO2 ) via organometallic decomposition route. As-prepared catalysts were thoroughly characterized using powder X-ray diffraction, electron microscopy, elemental analysis, vibrating sample magnetometer, and X-ray photoelectron spectroscopy techniques. High conversion and selectivity toward methane were observed at mid-temperature range, hence improving energy efficiency of the process with respect to the previous results under magnetic heating conditions. To gain further insight into the catalytic system, the effects of the synthesis method and of 0.5 wt % Ru doping were evaluated. Finally, the dynamic nature of magnetically induced heating was demonstrated through fast stop-and-go experiments, proving the suitability of this technology for the storage of intermittent renewable energy through P2G process.

Chemical fixation of CO2 with epoxides catalyzed by DBO as activator for the LiI promoted system: A theoretical study

Chemical fixation of carbon dioxide into value-added products is a promising idea. However, its conversion to valuable organic compounds requires highly efficient and safe catalytic system. In this work, the catalytic efficiency of the nontoxic organic base 1, 4‑Diazabicyclo Oct-4-ene (DBO) and its improved result after it has been cooperated with LiI salt have been studied. We gained more insight into the catalytic effects of DBO/LiI on the fixation of CO2 by means of density functional theory calculations using exchange–correlation functional B3LYP through basis sets of LANL2DZ for iodine and 6–31 + G(d,p) for non-iodine atoms. The calculations were carried out in both gas phase and in the presence of water as a solvent. Two reaction mechanisms were proposed and their respective energy was investigated to identify the favorable path for DBO/LiI system catalyzed reaction. Mechanism I is more favorable, in which the ring-opening of epoxide is the rate-limiting step which demands 32.20 kcal mol−1 Gibbs free energy of activation in the gas phase and 20.60 kcal mol-1in water. Lastly, this work validates that DBO in the presence of LiI displayed better catalytic activity for the title reaction and water is a good solvent for DBO/LiI catalyzed cycloaddition of CO2 with an epoxide.

Chiral aldehyde-nickel dual catalysis enables asymmetric α−propargylation of amino acids and stereodivergent synthesis of NP25302

The combined catalytic systems derived from organocatalysts and transition metals exhibit powerful activation and stereoselective-control abilities in asymmetric catalysis. This work describes a highly efficient chiral aldehyde-nickel dual catalytic system and its application for the direct asymmetric α−propargylation reaction of amino acid esters with propargylic alcohol derivatives. Various structural diversity α,α−disubstituted non-proteinogenic α−amino acid esters are produced in good-to-excellent yields and enantioselectivities. Furthermore, a stereodivergent synthesis of natural product NP25302 is achieved, and a reasonable reaction mechanism is proposed to illustrate the observed stereoselectivity based on the results of control experiments, nonlinear effect investigation, and HRMS detection.

Platinum supported on hydroxyl-grafted poly (3,4-ethylenedioxythiophene)-modified RuCo, N-tridoped bamboo-like carbon nanotubes for direct methanol fuel cell

The development of highly active and efficient heterogeneous catalytic oxidation system has become an attractive research field. In this paper, a catalyst (RuCo/N-CNT@PEDOT-OH/Pt) from platinum nanoparticles (Pt NPs) supported on hydroxyl-grafted poly(3,4-ethylenedioxythiophene) (PEDOT–OH)-modified RuCo, N-tridoped bamboo-like carbon nanotubes (RuCo/N-CNT) are used for direct methanol fuel cell (DMFC). The electrocatalytic activity of RuCo/N-CNT@PEDOT-OH/Pt is systematically compared with RuCo/N-CNT/Pt (Pt NPs supported on RuCo/N-CNT without PEDOT-OH) in the methanol oxidation reaction (MOR). The growth mechanism of carbon nanotubes and the role of heteroatom doping in the electrocatalytic process is explored. The catalysts show excellent electrocatalytic performance with high stability for MOR. It is found that the mass activity (MA) of the RuCo/N-CNT@PEDOT-OH/Pt (1961.3 mA mg−1Pt) for MOR was higher than that of RuCo/N-CNT/Pt (1470.1 mA mg−1Pt) and the commercial Pt/C catalysts (281.0 mA mg−1Pt), indicating the positive effect of the PEDOT-OH in the electrocatalytic MOR. In addition, density functional theory (DFT) calculations verify the possible mechanism pathways of the obtained RuCo/N-CNT@PEDOT-OH/Pt catalyst. This presented catalyst offers new inspiration for designing efficient electrocatalysts for methanol oxidation.

Construction of a Magnetic γ‐Fe2O3/h‐BN Composite for Tetracycline Degradation by Visible‐Light‐Initiated Peroxydisulfate

AbstractDeveloping a novel and highly efficient catalytic oxidation system for environmental protection was an important task. In this work, inspired by the photocatalytic system and peroxydisulfate (PDS) system, the magnetic γ‐Fe2O3/h‐BN composite was designed for synergetic catalytic. The tetracycline was selected to study the degradation activity of all‐obtained samples. Among, the sample with a weight ratio of 7 % has the optimum catalytic performance. The enhanced catalytic performance was attributed to the separation of electron‐hole pairs and contact with pollutant of γ‐Fe2O3/h‐BN composite. Under visible‐light illumination, the γ‐Fe2O3/h‐BN composite could generate superoxide free radicals (O2.−)) and holes (h+) to decompose pollutant, while the addition of PDS, the PDS would excite to generate hydroxyl radicals (⋅OH) and sulfate radicals (SO4.−) for further degrading pollutant. Under optimal condition, the degradation rate reached 90 % within 90 min. In addition, the investigation of tetracycline (TC) degradation under different experimental conditions (pH, catalyst dosage, PDS concentration, various salt) was conducted. This study provided a novel synergetic catalytic system for wastewater treatment.

Optimal Balance in the Catalyst Dynamics Enables C(2)−H Arylation of (Benz)imidazoles and (Benz)oxazoles by an In Situ‐Generated Ni/NHC System

AbstractAn efficient method for the C(2)−H arylation of (benz)imidazoles and (benz)oxazoles with aryl chlorides and aryl bromides under Ni/NHC catalysis has been developed. The main benefit of the method is the in situ generation of active Ni/NHC complexes from the air‐tolerant bench‐stable precursors NiCl2Py2, IMes⋅HCl, and potassium tert‐butoxide, which plays a dual role as base and Ni(II) to Ni(0) reductant. The approach represents a user‐friendly alternative for procedures relying on the use of toxic phosphine ligands or unstable air‐sensitive Ni(cod)2. The concept highlighted in the present study shows that mapping a competitive picture of catalyst dynamics and revealing the competitive processes towards the destruction and stabilization of catalytically active species enables a highly efficient catalytic system to be built under simple conditions.

Enhancing CO2 electroreduction to syngas by active protons of imidazolium ionic liquids: From performance to mechanism

High current density at specific CO/H2 molar ratios is the key to the industrial application of heterogeneous electrocatalytic CO2 reduction reaction (CO2RR) to syngas, which is still very challenging. Here, we report a Ni-foam-supported nano-Ag catalyst for CO2RR in ionic liquid (IL)-acetonitrile electrolyte originally designed for CO2RR-to-CO. It is surprising to find that this is a highly efficient catalytic system for CO2RR-to-syngas, the CO/H2 molar ratio in the syngas can be tuned from 1:5–26:1, and the current density is as high as 363.6, 458.2, and 644.7 mA cm−2 at the CO/H2 molar ratios of 1:1, 1:2, and 1:3, respectively. The high efficiency of CO2RR-to-syngas is attributed to the synergistic stabilization action of nano-Ag and IL cationic C4/5-H for intermediate *COO- to produce CO, as well as cationic C2-H contribution to hydrogen evolution. This work opens a new way to improve catalytic performance of CO2RR-to-syngas.