Aerobic Oxidation Of Alcohols Research Articles

Innovative development of hybrid nanocatalyst (ATH-ZnONPs) through green methods for achieving visible light-induced photocatalytic aerobic oxidation of benzyl alcohols into corresponding aldehydes and ketones

In recent research, there has been a surging interest in green methods for manufacturing metal oxide photocatalysts and enabling organic transformations in gentle conditions. This study achieved a groundbreaking development, introducing zinc oxide nanoparticles sensitized with anthocyanin dye (ATH-ZnONPs) for the very first time. The reducing agents in pomegranate leaves were utilized to synthesize ZnONPs from zinc salt. Simultaneously, anthocyanin dye was extracted from pomegranate flowers and linked with the ZnONPs. The FT-IR functional group analysis provided evidence of the successful conjugation of ZnONPs and ATH dye. SEM, EDX, and Elemental Mapping analysis unveiled the spherical morphology and nanocrystalline structure of ATH-ZnONPs, with particle sizes falling within the range of 50–70 nm. XRD analysis verified the hexagonal structural configuration of ZnONPs within the hybrid nanocomposite, with calculated lattice parameters of a = 3.261 Å and c = 5.207 Å. UV–Vis and DRS spectroscopy demonstrated that the composite efficiently harnesses visible light irradiation, exhibiting an energy bandgap of 2.22 eV. The assessment of ZnONPs through BET analysis unveiled a pore volume of 0.053 cm3/g, an SSA of 14.223 m2/g, and an average pore size of 4.18 nm, underscoring the mesoporous characteristics of ZnONPs. Importantly, the photocatalytic performance of the synthesized ATH-ZnONPs was thoroughly examined under blue LED light exposure. This investigation encompassed the evaluation of catalyst dosage, the impact of the light source, stability, regeneration, and the potential for reuse in the aerobic oxidation of benzyl alcohols, resulting in their corresponding aldehydes and ketones. 1HNMR and 13CNMR were used to characterize the products. The results of these studies highlight the versatile potential of this composite for a wide range of photocatalytic applications.

Flowerlike Nanosheet-Based High-Entropy Oxides as Catalysts for Aerobic Oxidation of Benzyl Alcohol

Flowerlike Nanosheet-Based High-Entropy Oxides as Catalysts for Aerobic Oxidation of Benzyl Alcohol

Cobalt-Centered Supramolecular Nanoensemble for Regulated Aerobic Oxidation of Alcohols and "One-Pot" Synthesis of Quinazolin-4(3H)-ones.

The supramolecular assemblies of the donor-acceptor (D-A) system Im-Tpy, having phenanthro[9,10-d]imidazole as the donor and terpyridyl group as the acceptor unit, have been developed, which serve as supramolecular host to stabilize Co(II) in its nanoform. The as-prepared supramolecular nanoensemble Im-Tpy@Co in DMSO:water (7:3) shows high thermal stability and photostability. Even in the case of solvent mismatch, i.e., on dilution with cosolvent THF/DMSO, insignificant changes were observed in the size/morphology of the nanoensemble. The as-prepared Im-Tpy@Co nanoensemble in low catalytic loading (0.1 mol % of Co) catalyzes the oxidation of a wide variety of alcohols to aromatic aldehydes/ketones using visible light radiations as the source of energy without the need of any additive at room temperature. In comparison to already reported systems, the Im-Tpy@Co nanoensemble exhibits high turnover numbers (TONs) and turnover frequencies (TOFs). The practical application of the catalytic system has also been demonstrated in the gram-scale synthesis of 4-chlorobenzaldehyde. The Im-Tpy@Co nanoensemble exhibits recyclability up to four catalytic cycles with insignificant leaching and morphological changes. The present study also demonstrates the catalytic activity of the Im-Tpy@Co nanoensemble in "one-pot" synthesis of quinazolin-4(3H)-ones from 2-aminobenzamide and primary alcohols with better efficiency in comparison to other transition-metal-based catalytic systems.

UV Cross-Linked Polymer Stabilized Gold Nanoparticles as a Reusable Dip-Catalyst for Aerobic Oxidation of Alcohols and Cross-Aldol Reactions

UV Cross-Linked Polymer Stabilized Gold Nanoparticles as a Reusable Dip-Catalyst for Aerobic Oxidation of Alcohols and Cross-Aldol Reactions

Cooperation of ultrathin bowl-shaped scaffolds and oxygen vacancies promoting selective photo-oxidation of aromatic alcohols on layered oxyhalide PbBiO2Cl

Photocatalytic selective oxidation of aromatic alcohols into value-added chemicals has attracted increasing attention. Yet most processes suffer from sluggish charge kinetics, weak O2 affinity, low conversion efficiency and selectivity, which restrict their practical development. Herein, PbBiO2Cl ultrathin bowls (UBs) with rich oxygen vacancies (ROV) were initially fabricated via a combined microemulsion method and in-situ reduction process. The ultrathin bowl-shaped geometry and rich OVs effectively boost light absorption and charge separation. Theoretical results indicate the OVs on PbBiO2Cl not only generate abundant localized electrons, but also afford strong interfacial covalent bonds between O2 and OVs, which can act as atomic-level electron transfer highway and effectively promote the O2 adsorption and activation. As a result, ROV-PbBiO2Cl UBs show a 5.2-fold enhanced activity for aerobic oxidation of alcohols to aldehydes relative to PbBiO2Cl nanoplates (NPs). This work may inspire the design of more open hollow scaffolds with defect engineering for artificial photosynthesis.

Development of sustainable green catalysts for oxidation of alcohols via decorated palladium nanoparticles on magnetic carbon nanotube/MOF

Using a straightforward method, this study fabricated an eco-friendly low-cost magnetic nanocomposite consisting of magnetic carbon nanotube/MOF as a stabilizer. Pd nanoparticles (Pd NPs) were then decorated on the designed magnetic carbon nanotube/MOF microspheres, and the resulting magnetic carbon nanotube/MOF/Pd NPs nanocomposite were employed as heterogeneous catalysts in Aerobic oxidation of primary and secondary alcohols. The attractiveness of this work is in the selective oxidation of several types of active and inactive alcohol substrates. The most important feature of this catalyst is its successful recovery and simple separation repeatedly without reducing its activity and selectivity. The active surface area of this Nanocatalyst is very large due to its structural properties, and as a result, it provides more available catalytic sites, which increases its activity. The identification techniques used to investigate the structural properties of this Nanocatalyst confirm its successful synthesis and appropriate palladium loading into the catalyst sites. The oxidation of alcohols was determined by Gas Chromatography (GC). The 100% selectivity, excellent turnover number (TON), high yield, almost complete and fast conversion of alcohol to the desired aldehydes and ketones without more oxidation, and easy and no-trouble isolation of product and catalyst are outstanding features of this catalytic system. The use of picolinaldehyde lead to the high loading of Pd NPs, reducing the catalyst content needed for the reaction. Regarding the high catalyst loading, using a small amount of catalyst is recommended for proceeding with the reaction efficiently.

Boosting the catalytic activity of Cu2O via forming composite with both Cu and metal oxides MO2 (M = Mo and W) by tuning its band structure and Lewis acidity

In this work, composite materials (Cu-Cu2O/MO2, M = Mo and W) and their thermally treated form were prepared and characterized by using a variety of spectroscopic techniques (XRD, SEM, HRTEM, XPS and UPS) and cyclic voltammetry. Their catalytic performance on aerobic oxidation of various alcohols under mild conditions was investigated with N-methylimidazole (NMI) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as the co-catalysts. Of the materials, the thermally treated MoO2-based material exhibited the best performance and durability. Compared to Cu-Cu2O, the involvement of MO2 significantly enhances the catalytic activity on the oxidation. Our results suggest that the presence of MO2 not only raises the energy level of VBM of Cu2O which is beneficial to O2 activation and generates internal electric field pointing to the catalytic center (Cu2O) which would accelerate the electron transfer from the substrate to the catalyst through forming heterojunction with both Cu and MO2, but also disperses the catalytic center. Further, the Lewis acidity of MO2 with appropriate strength can bring the substrate closer to the catalytic center via adsorption. But appropriate acidity is essential as easy on–off adsorption is desired in the catalysis. Thermal treatment generates oxidation state VI species of stronger acidity which offsets the effect of the raised VBM energy level.

Polyacrylonitrile/cellulose nanofiber supported gold nanoparticles for liquid-phase aerobic oxidation of benzyl alcohol to benzaldehyde

Polyacrylonitrile/cellulose nanofiber supported gold nanoparticles for liquid-phase aerobic oxidation of benzyl alcohol to benzaldehyde

Biosynthesis of vanillin from vanillyl alcohol by recombinant Escherichia coli cells expressing 5-hydroxymethylfurfural oxidase

The efficient valorization of lignin-derived vanillyl alcohol for the production of value-added biovanillin with enzyme or whole-cell based biotransformation is attracting increasing attention. In this study, a recombinant Escherichia coli HMFO was explored for the production of vanillin through the selective aerobic oxidation of vanillyl alcohol. The resting cells of this strain indicated a high vanillin tolerance and good biocatalytic activity over a temperature range of 10–35 °C. The vanillyl alcohol oxidation process produced vanillin as the sole product, indicating excellent reaction selectivity. Vanillyl alcohol substrate of 250 mM was converted to vanillin under optimal conditions with 96 % yield. In addition, 449.2 mM vanillin was obtained in a fed-batch experiment, providing a productivity of 1.2 g/L per hour and 90 % yield. The production of biovanillin could be further improved by using enzyme engineering and process engineering methods.

Copper Nanoparticles Supported on ZIF-8: Comparison of Cu(II) Reduction Processes and Application as Benzyl Alcohol Oxidation Catalysts.

We report the synthesis of a stable heterogeneous catalyst based on copper metal nanoparticles with oxidized surface supported on ZIF-8 for the oxidation of benzyl alcohol under mild temperature and using air as a sustainable oxygen source as well as for the implementation of the tandem "one-pot" catalytic system allowing the sustainable synthesis of benzylidene malononitrile. The influence of the reduction process applied to form the nanoparticle upon the catalyst texture and its performances was extensively examined. After ZIF-8 impregnation with a copper chloride precursor, the reduction of cupric ions into Cu0 nanoparticles was carried out according to two procedures: (i) by soaking the solid into a solution of NaBH4 and (ii) by submitting it to a flow of gaseous H2 at 340 °C. The in-depth physicochemical characterization and comparison of the resulting two types of Cu/ZIF-8 materials reveal significant differences: the reduction with NaBH4 led to the formation of 16 nm sized Cu0 nanoparticles (NP) mainly localized on the external surface of the ZIF-8 crystals together with ZnO nanocrystallites, while the reduction under H2 flow resulted in Cu0 nanoparticles with a mean size of 22 nm embedded within the bulk of ZIF-8 crystals. More, when NaBH4 was used to reduce cupric ions, ZnO particles were highlighted by high-resolution microcospy imaging. Formation of ZnO impurities was confirmed by the photoluminescence analysis of ZIF-8 after NaBH4 treatment. In contrast, ZnO was not detected on ZIF-8 treated with H2. Both types of Cu0 NPs supported on ZIF-8 were found to be active as catalysts toward the aerobic oxidation of benzyl alcohol under moderate temperature (T < 80 °C) and using air as a sustainable O2 source. Benzaldehyde yield of 66% and selectivity superior to 90% were obtained with the Cu/ZIF-8 catalyst prepared under H2 flow after 24 h under these conditions. The same material could be recycled 5 times without loss of activity, unlike the catalysts synthesized with NaBH4, as a result of the leaching of the surface copper NPs over the consecutive catalytic cycles. Finally, the most stable catalyst was successfully implemented in a tandem "one-pot" catalytic system associating benzyl alcohol oxidation and Knoevenagel condensation to synthesize benzylidene malononitrile.

Efficient aerobic oxidation of alcohols and sulfides using an M-doped (M: Mn and Ni) zinc oxide nanostructure

The generation of aldehydes and sulfoxides through selective oxidation process plays an essential role in different organic synthesis. However, using or toxic solvents under harsh reaction conditions leads to wastes and undesired by-products. With this background, ultrafast one-step fabrication of Ni/Mn doped-ZnO was developed under ultrasonic agitation for the first time. The resulting nanostructure was characterized by XRD, SEM, TEM, and BET analysis. According to data, a single-phase ZnO structure (wurtzite type) with uniform morphology, and acceptable surface area was obtained for the prepared nanocatalyst. Next, the catalytic activity of the nanostructure was investigated in aerobic oxidation of aliphatic and benzylic alcohols and sulfides. Notably, the present work is the first report of using ultrasound-engendered Ni/Mn doped-ZnO for selective aerobic oxidation reactions. It was found that the proposed nanostructure represented a novel chemical function for catalyzed alcohols and sulfides oxidation with excellent yields and selectivity without using any additives.

Aerobic oxidation of benzylic alcohols catalysed by new (aryl‐BIAN)copper(I) complexes: Their synthesis and structural characterization

A new neutral dimeric Ar‐BIAN Cu(I) complex (where Ar‐BIAN = bis(aryl‐imino)acenaphthene) of formulation [CuBr(4‐iPrC6H4‐BIAN)]2 (2) was obtained by reacting CuBr and ligand 4‐iPrC6H4‐BIAN (L2) in refluxing acetonitrile under an argon atmosphere. When the ligand used was 2,4,6‐Me3C6H2‐BIAN (L1), we obtained 1 in which the expected dimer (1a) is present, but we could also observe, in solution, the presence of the bis‐chelate dimer [Cu(2,4,6‐Me3C6H2‐BIAN)2][CuBr2] (1b) bearing CuBr2− as counter‐ion; attempts to separate them failed. When the ligand used was 2‐iPrC6H4‐BIAN (L3), we obtained 3 in which the expected dimer (3a) is in equilibrium, in solution, with its bis‐chelate isomer [Cu(2‐iPrC6H4‐BIAN)2][CuBr2] (3b). The solid‐state molecular structures of compounds 2 and 3b were determined by single crystal X‐ray diffraction. The electrochemical behaviour of complexes: 1 (1a, and 1b), 2, and 3 (3a and 3b) and the known compound [Cu(2‐iPrC6H4‐BIAN)2][BF4] (7) were investigated by cyclic voltammetry. The new complexes 1 (1a, 1b), 2, and 3 (3a, 3b) were tested as catalysts for the aerobic oxidation of benzylic alcohols into aldehydes; they all catalyse the reaction, with good results; the catalytic studies were extended to the similar known complexes [CuBr(2,6‐iPr2C6H3‐BIAN)]2 (4), [CuI(2,6‐iPr2C6H3‐BIAN)]2 (5), [CuCl(2,6‐iPr2C6H3‐BIAN)]2 (6) and (7), in order to study the effect of different bridging halides or counter ions in the catalytic activity. We found that compound 4 exhibited a high catalytic activity comparable to the best results published so far. The oxidation products, benzaldehydes, were detected and further confirmed by NMR spectroscopy, and the conversion rate was determined after GC‐FID analysis.

Discovery of the Quinoxalinone-B(C6F5)3·H2O Combo as a Photocatalyst by Acidochromism Strategy: Aerobic Oxidation of Alcohol, Alkene, and Thiols.

Modification of photocatalyst reactivity through intermolecular interactions represents a straightforward and convenient strategy for catalyst designation. Herein, we reported that upon the addition of B(C6F5)3·H2O, the oxidation potential of quinoxalinone increased remarkably, enabling the photoredox aerobic oxidation of alcohol, thiols, and alkenes toward carbonyl compounds and dithioethers under visible light conditions. Mechanistic studies, including X-ray structure analysis, cyclic voltammetry, electron paramagnetic resonance measurements, UV-vis absorption, and fluorescence spectra, revealed that the quinoxalinone-B(C6F5)3·H2O combo could serve as a versatile photocatalyst for both energy transfer and single electron transfer processes.

TEMPO immobilization on activated carbon by a novel surface-formylation tactic for long-term aerobic oxidation of alcohols

2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has vital applications in the field of multiphase reaction, especially for the aerobic oxidation of alcohols. Activated carbon (AC) has a porous structure, rigid surface property, and low cost, which was the prominent carrier for TEMPO immobilization to produce the heterogeneous catalyst. However, the brilliant strategy of TEMPO immobilization on AC for long-term aerobic oxidation of alcohols was still challenging. In this work, surface-formylation and reductive amination were conducted to achieve the covalent TEMPO grafting on AC, which opened up a novel routine for surface modification and preparing heterogeneous catalysts based on carbon materials. The catalysts were packed in a micro-packed bed reactor to perform continuous aerobic oxidation of various alcohols. The catalytic performance of benzyl alcohol to benzaldehyde (turnover number: 1160.6, turnover frequency: 99.6 h−1) was much superior to those in the literature by using covalently grafted heterogeneous TEMPO catalysts.

Efficient Dual-Function Catalyst: Palladium-Copper Nanoparticles Immobilized on Co-Cr LDH for Seamless Aerobic Oxidation of Benzyl Alcohol and Nitrobenzene Reduction.

Layered double hydroxides (LDHs) present exciting possibilities across various industries, ranging from catalytic applications to water remediation. By immobilizing nanoparticles, LDHs' characteristics and functionality can be enhanced, allowing for synergetic interactions that further expand their potential uses. A simple chemical method was developed to produce well-dispersed Pd-Cu NPs on a Co-Cr LDH support using a combination of in situ coprecipitation/hydrothermal and sol-immobilization techniques. The Pd-Cu@Co-Cr LDH catalysts was obtained, showing its catalytic activity in promoting the aerobic oxidation of alcohols and enabling the reduction of nitro-compounds through NaBH4 mediation. The physicochemical properties of the prepared catalyst were comprehensively investigated utilizing a range of analytical techniques, comprising FTIR, XRD, XPS, TGA, nitrogen adsorption isotherm, FESEM, and HRTEM-EDX. The findings showed the significance of immobilizing the bimetallic Pd-Cu nanoparticles on the Co-Cr LDH via an exceptional performance in the aerobic oxidation of benzyl alcohol (16% conversion, 99.9% selectivity to benzaldehyde) and the reduction of nitrobenzene (98.2% conversion, rate constant of 0.0921 min-1). The improved catalytic efficacy in benzyl alcohol oxidation and nitrobenzene reduction on the Pd-Cu@Co-Cr LDH catalyst is attributed to the uniform distribution and small size of the Pd-Cu NPs as active sites on the Co-Cr LDH surface. The prepared catalyst demonstrated exceptional stability during repeated runs. This study paves the way for multiple opportunities in tailoring, producing, and precisely controlling catalysts for various organic transformation reactions.

Highly selective and stable polybenzoxazine-based carbon nanosheet supported Pd catalyst for aerobic benzyl alcohol oxidation

Highly selective and stable polybenzoxazine-based carbon nanosheet supported Pd catalyst for aerobic benzyl alcohol oxidation

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions.

We report on the high potential of a honeycomb reactor for the use in aerobic oxidation under continuous-flow conditions. The honeycomb reactor is made of porous material with narrow channels separated by porous walls allowing for high density accumulation in the reactor. This structure raised the mixing efficiency of a gas-liquid reaction system, and it effectively accelerated the aerobic oxidation of benzyl alcohols to benzaldehydes under continuous-flow conditions. This reactor is a promising device for streamlining aerobic oxidation with high process safety because it is a closed system.

Selective aerobic oxidation of benzyl alcohol under ambient conditions using polyionic nanoclay-supported gold/palladium nanoparticles

Oxidation of alcohols to their respective aldehydes, esters, and acids is a common value-added industrial process, though techniques often rely on harsh reaction conditions (e.g., high temperature, strong base, organic solvents, hydrothermal processes) to achieve rapid reaction turnovers. The incorporation of gold and palladium nanoparticles facilitates the dehydrogenation and O2 reduction processes, respectively, and these advantages can be dually incorporated and enhanced using supported nanoparticle alloys. Herein, we utilize polyionic nanoclays (PINCs) as two-dimensional inorganic-organic architectures for supporting monometallic and bimetallic gold and palladium nanocatalysts for the model oxidation of benzyl alcohol to the corresponding aldehyde, ester, and acid. In addition, we present two new PINC surface chemistries (N-methylpyrrolidinium- and pyridinium-functionalized PINCs) and compare their performances as catalyst supports to show that catalyst enhancement is altered by the PINC surface chemistry. Reaction conditions are mild (aqueous, room temperature, open to atmosphere, weak or no base) yet reaction turnovers are comparable to those of more demanding literature accounts.

Visible-light Aerobic Oxidation of Benzyl Alcohol over Porphyrin-sensitized Titanium Dioxide Photocatalysts

Visible-light Aerobic Oxidation of Benzyl Alcohol over Porphyrin-sensitized Titanium Dioxide Photocatalysts

Facile synthesis of CoSi alloy catalysts with rich vacancies for base- and solvent-free aerobic oxidation of aromatic alcohols

The rational design and green synthesis of low-cost, robust, and efficient catalysts for the selective oxidation of various alcohols are highly challenging. Herein, we report a fast and solvent-free arc-melting (AM) method to controllably synthesize a semimetallic CoSi alloy catalyst (denoted as AM-CoSi) that is efficient in the base- and solvent-free oxidation of six types of aromatic alcohols. X-ray absorption fine structure analysis, electron paramagnetic resonance spectroscopy, and aberration-corrected high angle annular dark field scanning transmission electron microscopy confirmed the successful synthesis of AM-CoSi with abundant Si vacancies (Siv). The as-prepared CoSi alloy catalysts exhibit an order of magnitude greater activity in the oxidation of a model reactant, benzyl alcohol (BAL) to benzyl benzoate (BBE), compared with their mono-counterparts, and provide 70% yield of BBE, the highest yield reported to date. Experimental results and density functional theory calculations suggest that the CoSi alloy structure improves the BAL conversion and that Si vacancy is the main contributor to the generation of BBE, based on which a potential reaction pathway is rationally proposed. Furthermore, the CoSi alloy maintains high stability and also exhibits high activity in the selective oxidation of various alcohols with different functional groups. This work demonstrates for the first time that semimetallic CoSi alloys can be robust catalysts for the green oxidation of various alcohols and proviedes a vast opportunity for the rational design and application of other semimetal alloy catalysts.