Hydroxylation Of Benzene Research Articles

Bacterial Acyl Homoserine Lactones Triggered Non‐Native Substrate Hydroxylation Catalyzed by Directed‐Evolution‐Derived Cytochrome P450BM3 Mutants

AbstractWe report the directed evolution of cytochrome P450BM3 to efficiently utilize the bacterial quorum sensing signalling molecule N‐decanoyl homoserine lactone (C10‐HSL) as an effective decoy molecule. This represents the first important step in our endeavor to develop of a self‐sufficient decoy‐molecule system in whole‐cells that only necessitates the addition of culture medium and substrate to realize the hydroxylation of non‐native substrates. Following five rounds of directed evolution, mutant P450BM3, in the presence of C10‐HSL, catalyzed the hydroxylation of benzene at a rate of 475 min−1, the highest turnover rate recorded for any P450 enzyme, and achieving a 46% yield in a whole‐cell reaction system. High‐resolution X‐ray crystal structure analysis of a series of mutants narrates the directed evolution process, revealing how C10‐HSL is fixed in the binding pocket to permit binding of non‐native substrates. Finally, introduction of the C10‐HSL synthase gene ExpI into Escherichia coli, enabled the in situ production of C10‐HSL, realizing, for the first time, the hydroxylation of non‐native substrates without the need for the laborious synthesis and addition of decoy molecules.

In situ preparation of highly active and selective Fe‐MOF/V‐C3N4 for photocatalytic hydroxylation of benzene to phenol

In situ preparation of highly active and selective Fe‐MOF/V‐C3N4 for photocatalytic hydroxylation of benzene to phenol

Visible-Light-Driven Oxidation of Benzene to Phenol with O2 over Photoinduced Oxygen-Vacancy-Rich WO3.

Direct photocatalytic conversion of benzene to phenol with O2 is a green alternative to the traditional synthesis. The key is to find an effective photocatalyst to do the trick. Defect engineering of semiconductors with oxygen vacancies (OVs) is an emerging strategy for catalyst fabrication. OVs can trap electrons to promote charge separation and serving as adsorption sites for O2 activation. However,randomly distribution of OVs on the semiconductor surface often results in mismatching the charge carrier dynamics under irradiation, thus failing to fulfill the unique advantages of OVs for photoredox functions. Herein, we demonstrate that abundant OVs can be facilely generated and precisely located adjacent to the reductive sites on reducible oxide semiconductors such as tungsten oxide (WO3) via a simple photochemistry strategy. Such photoinduced OVs are well suited for photocatalytic benzene oxidation with O2 as they readily capture photogenerated electrons from the reductive sites of WO3 to activate adsorbed O2. 18O-labeling experiments further confirm that the OVs also facilitate the integration of oxygen atoms from O2 into phenol, revealing in detail the pathway for photocatalytic benzene hydroxylation. This study demonstrates that the photochemistry approach is an appealing strategy for the synthesis of high-performance OVs-rich photocatalysts for solar-induced chemical conversion.

Visible‐Light‐Driven Oxidation of Benzene to Phenol with O2 over Photoinduced Oxygen‐Vacancy‐Rich WO3

Direct photocatalytic conversion of benzene to phenol with O2 is a green alternative to the traditional synthesis. The key is to find an effective photocatalyst to do the trick. Defect engineering of semiconductors with oxygen vacancies (OVs) is an emerging strategy for catalyst fabrication. OVs can trap electrons to promote charge separation and serving as adsorption sites for O2 activation. However, randomly distribution of OVs on the semiconductor surface often results in mismatching the charge carrier dynamics under irradiation, thus failing to fulfill the unique advantages of OVs for photoredox functions. Herein, we demonstrate that abundant OVs can be facilely generated and precisely located adjacent to the reductive sites on reducible oxide semiconductors such as tungsten oxide (WO3) via a simple photochemistry strategy. Such photoinduced OVs are well suited for photocatalytic benzene oxidation with O2 as they readily capture photogenerated electrons from the reductive sites of WO3 to activate adsorbed O2. 18O‐labeling experiments further confirm that the OVs also facilitate the integration of oxygen atoms from O2 into phenol, revealing in detail the pathway for photocatalytic benzene hydroxylation. This study demonstrates that the photochemistry approach is an appealing strategy for the synthesis of high‐performance OVs‐rich photocatalysts for solar‐induced chemical conversion.

Effects of hydrothermal pretreatment on sulfadiazine degradation during two-stage anaerobic digestion of pig manure

Antibiotics in animal manure pose significant risks to the environment and health. While anaerobic digestion (AD) is commonly used for pig manure treatment, its efficiency in antibiotic removal has been considerably limited. This study investigated the impact of hydrothermal pretreatment (HTP) on sulfadiazine (SDZ) removal in a two-stage AD system. Results indicated that the HTP process reduced SDZ concentration by 40.61%. Furthermore, the SDZ removal efficiency of the AD system coupling HTP increased from 50.90% to 65.04% compared to the untreated system. Biogas yield was also improved by 26.17% while maintaining system stability. Changes induced by HTP in the microbial communities revealed that Firmicutes, Bacteroidetes, Caldatribacteriota, and Proteobacteria emerged as the primary bacterial phyla. Following HTP, the relative abundance of Prevotella, which exhibited a strong negative correlation with SDZ concentration, increased significantly by 25-fold in the acidogenic stage. Proteiniphilum, Syntrophomonas and Sedimentibacter showed notable increases in the methanogenic stage after HTP. The N-heterocyclic metabolism carried out by Prevotella might have been the predominant SDZ degradation pathway in the acidogenic stage, while the benzene ring metabolism and hydroxylation by the Proteiniphilum emerged as the primary degradation pathways in the methanogenic stages. Furthermore, biodegradation intermediates were proven to be less toxic than SDZ itself, indicating that the HTP-enhanced two-stage AD process could be a viable way to lower the environmental risks associated with SDZ. The findings from this study provide valuable insights for removing SDZ from the environment via two-stage AD.

Confined Cu Single Sites in ZSM‐5 for Photocatalytic Hydroxylation of Benzene to Phenol

Confined Cu Single Sites in ZSM‐5 for Photocatalytic Hydroxylation of Benzene to Phenol

An innovative biphasic reaction system for highly selective benzene hydroxylation based on photocatalytic polymer composites

The hydroxylation of benzene to phenol in presence of hydrogen peroxide was performed using a new biphasic system consisting of a solid phase, a photocatalytically active monolithic polymer composite, immersed in an aqueous phase in which H2O2 is dissolved. In detail, ZnO photocatalytic particles were embedded into the hydrophobic syndiotactic polystyrene (sPS) polymer. Zinc oxide nanostructures (ZnO NSs) were synthesized by an electrochemical procedure. The surface morphology and structure of ZnO nanoparticles and ZnO‐sPS monolithic aerogel composite (ZnO/sPS) were investigated by scanning electron microscopy, X‐ray diffraction and X‐ray photoelectron spectroscopy analysis. Photocatalytic results evidenced that, under UV irradiation, both ZnO NSs and biphasic system water‐photocatalytic composites had a high benzene oxidative property but with very low phenol yield (<2%) at pH=7. To enhance the phenol selective formation, the pH of aqueous solution surrounding the photocatalytic polymer composite was modified. A phenol yield of about 94% and benzene conversion higher than 99% was obtained in alkaline conditions (pH=11).

Continuous Flow Hydroxylation of Benzene to Phenol in a Photocatalytic Millistructured Flat-Plate Reactor

Continuous Flow Hydroxylation of Benzene to Phenol in a Photocatalytic Millistructured Flat-Plate Reactor

Highly efficient and sustainable photocatalytic Fenton reactions utilizing catalyst-embedded inverse-opal structured membranes

The inverse opal (IO) structure, known for its photonic crystal properties and uniform pores, promotes multiple internal light scatterings and reflections. This leads to a decrease in photon group velocity, generating a slow photon effect. When integrated with photocatalysts, this effect enhances light absorption by extending photon interaction with the catalyst, thereby significantly enhancing the efficacy of IO structures in photocatalytic applications. However, the integration of inorganic photocatalysts into IO structures presents challenges, such as mechanical brittleness and a tendency to form powders. To overcome these obstacles, we have engineered IO-structured polymeric membranes coated with graphitic carbon nitride tailored for photocatalytic Fenton reactions. These membranes, which encapsulate photocatalysts within the polymeric porous IO framework, facilitate the straightforward reaction and separation of catalysts from byproducts. They demonstrated superior photocatalytic performance, as evidenced by Rhodamine B degradation (∼7.1 %) and benzene hydroxylation (∼7.3 %). Extensive durability (>30 days) and recyclability tests (>5 times) confirmed their robustness, establishing their utility for various organic conversion reactions. By combining the advantages of the IO structure with tailored photocatalytic properties, these membranes offer promising potential for sustainable and efficient water treatment and the production of fine chemicals in industrial settings.

One-Step Benzene Hydroxylation with Copper Oxide Supported on Activated Red Mud Catalyst

One-Step Benzene Hydroxylation with Copper Oxide Supported on Activated Red Mud Catalyst

Vanadium-Modified TS-1 Catalysts with Enhanced Lewis Acid and Charge Density for Efficient Hydroxylation of Benzene to Phenol

Vanadium-Modified TS-1 Catalysts with Enhanced Lewis Acid and Charge Density for Efficient Hydroxylation of Benzene to Phenol

Highly Active and Selective Fe‐MOF/2D‐Montmorillonite Photocatalyst via in‐situ Preparation for Hydroxylation of Benzene to Phenol

AbstractThe photocatalytic hydroxylation of benzene to phenol is an important reaction for the synthesis of fine chemicals and pharmaceuticals. However, the development of efficient and selective photocatalysts for this reaction remains a challenge. Here, a highly active and selective Fe‐MOF/2D‐montmorillonite (Fe‐MOF/MMT) photocatalyst was prepared via an in‐situ method for the hydroxylation of benzene to phenol under the visible light irradiation. The Fe‐MOF/MMT composite exhibited excellent photocatalytic performance, with phenol yield of 30.3 % and benzene selectivity of 96.5 % within 4 hours. The high activity and selectivity of the Fe‐MOF/MMT photocatalyst were attributed to the synergistic effect between the Fe‐MOF and MMT, as well as the unique 2D structure of MMT, which facilitated charge separation and transfer. The Fe‐MOF/MMT composite also showed good stability and re‐used without significant decrease of activity. This study demonstrated that the potential of Fe‐MOF/MMT as a highly efficient and selective photocatalyst for the hydroxylation of benzene to phenol and provided an insight into the design of advanced photocatalysts for sustainable chemical synthesis.

Metal-Organic Framework-Supported Mono Bipyridyl-Iron Hydroxyl Catalyst for Selective Benzene Hydroxylation into Phenol.

Direct hydroxylation of benzene to phenol is more appealing in the industry for the economic and environmentally friendly phenol synthesis than the conventional cumene process. We have developed a UiO-metal-organic framework (MOF)-supported mono bipyridyl-Iron(II) hydroxyl catalyst [bpy-UiO-Fe(OH)2] for the selective benzene hydroxylation into phenol using H2O2 as the oxidant. The heterogeneous bpy-UiO-Fe(OH)2 catalyst showed high activity and remarkable phenol selectivity of 99%, giving the phenol mass-specific activity up to 1261 mmolPhOHgFe-1 h-1 at 60 °C. Bpy-UiO-Fe(OH)2 is significantly more active and selective than its homogeneous counterpart, bipyridine-Fe(OH)2. This enhanced catalytic activity of bpy-UiO-Fe(OH)2 over its homogeneous control is attributed to the active site isolation of the bpy-Fe(OH)2 moiety by the solid MOF that prevents intermolecular decomposition. Moreover, the exceptional selectivity of bpy-UiO-Fe(OH)2 in benzene to phenol conversion is originated via shape-selective catalysis, where the confined reaction space within the porous UiO-MOF prevents the formation of larger overoxidized products such as hydroquinone or benzoquinone, leading to the formation of only smaller-sized phenol after monohydroxylation of benzene. Spectroscopic and controlled experiments and theoretical calculations elucidated the reaction pathway, in which the in situ generated •OH radical mediated by bpy-UiO-FeII(OH)2 is the key species for benzene hydroxylation. This work underscores the significance of MOF-supported earth-abundant metal catalysts for sustainable production of fine chemicals.

Amorphous Vanadium Oxide Supported on Activated Carbon Prepared by Dielectric Barrier Discharge as an Efficient and Stable Catalyst for Hydroxylation of Benzene to Phenol

Amorphous Vanadium Oxide Supported on Activated Carbon Prepared by Dielectric Barrier Discharge as an Efficient and Stable Catalyst for Hydroxylation of Benzene to Phenol

DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H2O2.

Introduction of oxygen into aromatic C-H bonds is intriguing from both fundamental and practical perspectives. Although the 3d metal-catalyzed hydroxylation of arenes by H2O2 has been developed by several prominent researchers, a definitive mechanism for these crucial transformations remains elusive. Herein, density functional theory calculations were used to shed light on the mechanism of the established hydroxylation reaction of benzene with H2O2, catalyzed by [NiII(tepa)]2+ (tepa = tris[2-(pyridin-2-yl)ethyl]amine). Dinickel(III) bis(μ-oxo) species have been proposed as the key intermediate responsible for the benzene hydroxylation reaction. Our findings indicate that while the dinickel dioxygen species can be generated as a stable structure, it cannot serve as an active catalyst in this transformation. The calculations allowed us to unveil an unprecedented mechanism composed of six main steps as follows: (i) deprotonation of coordinated H2O2, (ii) oxidative addition, (iii) water elimination, (iv) benzene addition, (v) ketone generation, and (vi) tautomerization and regeneration of the active catalyst. Addition of benzene to oxygen, which occurs via a radical mechanism, turns out to be the rate-determining step in the overall reaction. This study demonstrates the critical role of Ni-oxyl species in such transformations, highlighting how the unpaired spin density value on oxygen and positive charges on the Ni-O• complex affect the activation barrier for benzene addition.

Development of an electrophotochemical flow microreactor for efficient electrophotocatalytic C-H hydroxylation of benzene to phenol

Electrophotocatalytic C-H hydroxylation of benzene is an emerging green technology with high potential for producing phenol in one step. However, it is still limited by efficiency and scale-up challenges in batch process. In this study, a novel electrophotochemical flow microreactor was designed and manufactured using 3D printing technology. Static mixers were incorporated to enhance the mixing. The effect of various parameters, such as electrode materials, reaction time, potential, and reactant concentration, etc., on the continuous synthesis of phenol in the as-developed microreactor was investigated. Furthermore, machine learning (ML) algorithms were employed to explore the impact of these parameters on the reaction efficiency. With cost-effective electrodes, higher phenol productivity was achieved in the present flow microreactor when comparing with batch counterpart and literature value. This study offers insights into the optimization of electrophotochemical microreactor for the hydroxylation of benzene, and provides guidance for exploring sustainable electrophotocatalytic organic synthesis in flow.

Generation and Reactivity of μ-1,2-Peroxo CuIICuII and Bis-μ-oxo CuIIICuIII Species and Catalytic Hydroxylation of Benzene to Phenol with Hydrogen Peroxide.

Tetradentate-N4 ligands stabilize dinuclear {CuII(μ-1,2-peroxo)CuII} and {CuIII(μ-O)2CuIII} species, and CuII complexes of these ligands were reported to catalyze the oxidation of benzene with H2O2. Here, we report {CuII(μ-1,2-peroxo)CuII} and {CuIII(μ-O)2CuIII} intermediates of dinucleating bis(tetradentate-N4) ligands depending on the absence or presence of 6-methyl substituents on the terminal pyridine donors, respectively, generated either from {CuICuI} precursors with O2 or from {CuIICuII} precursors with H2O2 and NEt3. Both intermediates are not stable even at low temperatures, but they show no electrophilic HAT reactivity with DHA. Catalytic investigations on the hydroxylation of benzene with excess H2O2 between 30 and 50 °C indicate that both radical-based and {Cu2On}-based mechanisms depend strongly on the catalytic conditions. In the presence of a radical scavenger, TONs of ∼920/∼720 have been achieved without/with the 6-methyl group of the ligand. Although {CuII(μ-OH)CuII} reacts with excess H2O2 at -40 °C to {CuII(OOH)}2 species, these are only stable for seconds at 20 °C and cannot account for catalytic oxidations over a period of 24 h at 30-50 °C.

Efficient catalytic direct C–H hydroxylation of benzene by graphite-supported μ-nitrido-bridged iron phthalocyanine dimer

Benzene was efficiently hydroxylated directly into phenol at room temperature in an acidic aqueous solution in the presence of hydrogen peroxide by using a graphite-supported μ-nitrido-bridged iron phthalocyanine dimer as a catalyst.

Copper-containing POM-based hybrid P2Mo22V4Cu4 nanocluster as heterogeneous catalyst for the light-driven hydroxylation of benzene to phenol.

The current traditional phenol production process has many shortcomings, and the efficient and clean photocatalytic one-step oxidation to phenol is gradually attracting attention. Heteropolyacids (PMo10V2) with high-density Lewis acid active sites and excellent photoelectron transfer ability are ideal choices for catalytic reactions. In this study, a copper-modified isolated dimeric hybrid nanocluster, [Cu(pyim)2]2[Cu(pyim)2(P2MoVI20MoV2VIV4O82)]2·(H2O) (pyim = [2-(pyridin-2-yl)imidazole]), was synthesized by a convenient hydrothermal method. The structural analysis demonstrated that the compound was composed of metal-organic complexes containing pyim ligands, Keggin-type heteropolyacids, and transition metal copper ions. Remarkably, this not only solves the difficulty that the heteropolymeric acid cannot be recovered by dissolving in the solvent but also introduces the copper atom as a second active center. The catalyst exhibited a benzene conversion of 15.6% and a selectivity of 85.2% in a mixed solution of acetonitrile and acetic acid under optimal reaction conditions. After four catalytic cycles, the PXRD pattern proved that the catalyst was still stable. This study provides a good idea for photocatalytic reactions and other environmental applications.

An iron-containing POM-based hybrid compound as a heterogeneous catalyst for one-step hydroxylation of benzene to phenol.

It is a major challenge to perform one-pot hydroxylation of benzene to phenol under mild conditions, which replaces the environmentally harmful cumene method. Thus, finding highly efficient heterogeneous catalysts that can be recycled is extremely significant. Herein, a (POM)-based hybrid compound {[FeII(pyim)2(C2H5O)][FeII(pyim)2(H2O)][PMoV2MoVI9VIV3O42]}·H2O (pyim = 2-(2-pyridyl)benzimidazole) (Fe2-PMo11V3) was successfully prepared by hydrothermal synthesis using typical Keggin POMs, iron ions and pyim ligands. Single-crystal diffraction shows that the Fe-pyim unit in Fe2-PMo11V3 forms a stable double-supported skeleton by Fe-O bonding to the polyacid anion. Remarkably, due to the introduction of vanadium, Fe2-PMo11V3 forms a divanadium-capped conformation. Benzene oxidation experiments indicated that Fe2-PMo11V3 can catalyze the benzene hydroxylation reaction to phenol in a mixed solution of acetonitrile and acetic acid containing H2O2 at 60 °C, affording a phenol yield of about 16.2% and a selectivity of about 94%.