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Hydroxylation of aryl sulfonium salts could be realized by utilizing acetohydroxamic acid and oxime as hydroxylative agents in the presence of cesium carbonate as a base, leading to a variety of structurally diverse hydroxylated arenes in 47–95% yields. In addition, the reaction exhibited broad functionality tolerance, and a range of important functional groups (e.g., cyano, nitro, sulfonyl, formyl, keto, and ester) could be well amenable to the mild reaction conditions. [ABSTRACT FROM AUTHOR]

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)][PMo V2 Mo VI9 V IV3 O42]}·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%. [ABSTRACT FROM AUTHOR]

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(P2Mo VI20 Mo V2 V IV4 O82)]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. [ABSTRACT FROM AUTHOR]

A new, improved 2nd generation route for the synthesis of 3‐ethyl‐4‐hydroxy‐5‐methylbenzonitrile has been developed. The original route started from 2‐ethyl‐6‐methylaniline, which was converted by a classical sequence of para‐bromination, cyanation and Sandmeyer hydroxylation into the desired phenol. This route was used on multi‐kg scale and delivered the product with the desired purity. However, the route was not ideal, as it featured safety critical steps (cyanation), employed undesirable solvents (DMF), included laborious workup and isolation procedures, and suffered from a low overall yield (40–45 %) and suboptimal green metrics (PMI: 210). We envisioned a new, non‐classical approach to the product by introducing the nitrile through a para‐selective formylation, followed by transformation of the intermediate aldehyde into the nitrile with hydroxylamine‐O‐sulfonic acid (HOSA). The new sequence of Sandmeyer hydroxylation, Duff formylation and HOSA‐promoted nitrile formation was thoroughly optimized and finally scaled up to 400 g. This novel 3‐step sequence delivered 3‐ethyl‐4‐hydroxy‐5‐methylbenzonitrile in 69 % overall yield with excellent purity (99.3 % a/a) and a vastly improved PMI of 81. [ABSTRACT FROM AUTHOR]

Phenols are one of the most important classes of raw materials in the chemical industry, and a variety of compounds are derived from them. The direct conversion of benzene to phenol by hydroxylation is an economical and environmentally friendly method among phenol syntheses, especially when such a reaction can be driven by solar energy. Herein, for the first, a CuO/Cu-MOF/GO photocatalyst which was facilely prepared from a single Cu-MOF/GO template by partial pyrolysis. Compared to completely pyrolysis, the CuO/Cu-MOF/GO got by partial pyrolysis exhibited significantly higher photocatalytic performance towards the hydroxylation of benzene to phenol. It was characterized in detail by SEM, XRD, FT-IR, UV–Vis-DRS, XPS, and N2 adsorption–desorption method. Its catalytic performance for direct hydroxylation of benzene to phenol has been investigated. The results showed that the conversion of benzene and the yield of phenol were 38.7% and 20.1% which were 4.1 times and 5.2 times higher than those using Cu-MOF/GO, respectively. The CuO/Cu-MOF/GO heterostructures showed remarkably enhanced photocatalytic activity toward the hydroxylation of benzene to phenol, which can be attributed to the band gap narrowing and enhanced photogenerated electron–hole separation ability. This work may provide useful guidance for the design of MOF-derived photocatalyst for the applications in the hydroxylation of aromatics. [ABSTRACT FROM AUTHOR]

Efficiently devising a strategy to synthesize titanium silicate-1 (TS-1) zeolite crystals with desired particle size and enriched framework titanium content for improved catalytic oxidation properties could be challenging. This study explores the incorporation of polyvinyl alcohol (PVA) and ammonium bicarbonate (NH4HCO3) as additives to decrease the particle size and increase the framework titanium content of TS-1, respectively. Powder X-ray diffraction (XRD), UV-vis absorption spectra, nitrogen adsorption–desorption, Fourier transform infrared (FT-IR) spectra, field-emission scanning electron microscopy (FESEM), and inductively coupled plasma (ICP) were used to characterize the TS-1 catalysts. The experimental results indicated that in the presence of NH4HCO3 and PVA (TS-1-S), the particle size and Si/Ti molar ratio of TS-1 were determined to be 170 nm and 43.55, respectively. Furthermore, the catalytic activity of the prepared catalysts in regard to the phenol hydroxylation with H2O2 has been evaluated. The TS-1-S sample showed a conversion of 29.52%, while the conversion of the conventional sample was 23.08%. This improvement can be attributed to the synergistic impact of reduced particle size and enriched framework titanium content. [ABSTRACT FROM AUTHOR]

We have developed a straightforward methodology for converting arylboronic acids into phenols using NaOH‐mediated air oxidation. This reaction offers several advantages, including simple operation, excellent tolerance towards various functional groups, and scalability. The transmetalation of the resulting borate ester with NaOH occurs readily, enabling convenient derivatization of the borate ester into aryl ethers and esters using alkyl and acyl halides. [ABSTRACT FROM AUTHOR]

Abstract This work highlighted the proficient and naturally safe methodology for the phenol synthesis using biocatalyst lipase. The development of sustainable synthetic protocol for various organic transformations is an important area of research attracts researchers to avoid use of volatile and hazardous organic solvents in reaction for greener and eco-friendly protocols. Lipase is subclass of esterase enzymes and acts as biocatalyst with industrial significance. They carry out biochemical transformation in non-aqueous and aqueous phases quickly. To further make the process more specific Design Expert software was used for the optimization of synthesize phenol for maximum % Yield and % Purity. Effect of temperature, Concentration of Catalyst, and Volume of Water was selected as an independent factor to get the maximum % Yield and % Purity of the phenol. The results confirmed the mathematical model robustness and justify experimental design. Therefore, the current protocol for synthesis of phenols from phenylboronic acid is greenest and environmentally benign alternative. The current convention has many benefits, like phenomenal product yields, reduced time of reaction, simple procedure to work up, and extensive substrate scope, cost-effective and also lipase was recuperated and reused multiple times without significant loss of its catalytic activity. [ABSTRACT FROM AUTHOR]

A highly organized hexagonal mesoporous iron phosphate framework structure with the designation HMI‐41 was successfully synthesized for the first‐time in a reproducible way using imidazolium‐based ionic liquid as structure directing agent. The unique templating properties of ionic liquid generated a highly ordered well‐crystallized mesoporous matrix having high surface area (445 m2 g−1), thicker pore wall (2.1 nm) and narrow pore size distribution (3.1 nm). The presence of active sites within a tetrahedral framework structure made the novel HMI‐41 catalyst highly effective for phenol hydroxylation in an acidic medium with hydrogen peroxide as the oxidant. The catalyst exhibited outstanding performance, achieving an impressive 80% hydroquinone selectivity and 21% phenol conversion with a hydroquinone‐to‐catechol ratio of seven, which is the highest value ever reported. [ABSTRACT FROM AUTHOR]

The enantioselective synthesis of violaceoid D, a cytotoxic phenolic compound isolated from the culture broth of Aspergillus violaceofuscus Gasperini, was achieved. The total synthesis involves stereoselective construction of the stereogenic center of violaceoid D via Sharpless asymmetric dihydroxylation, followed by Smiles rearrangement. The absolute configuration of natural violaceoid D was determined to be R from the specific rotation value. Synthesized violaceoid D and its analogs were evaluated for cytotoxicity against two human cancer cell lines, Jurkat and HCT116. Because the enantiomer of violaceoid D showed no cytotoxicity, it is plausible that violaceoid D binds selectively to specific target molecules, such as proteins in the cancer cells. [ABSTRACT FROM AUTHOR]

Cu(II) complexes supported by tetradentate amido-quinoline acyclic ligands (L1 & L2) have been synthesized, characterized, and employed as catalysts for aromatic C–H hydroxylation using H2O2 as an oxidant in the absence of an external base with a high selectivity of around 90% for phenols via the non-radical pathway (TON ≥720). The KIE value, various spectroscopic studies and DFT calculation supported the involvement of Cu(II)–OOH species. [ABSTRACT FROM AUTHOR]

Direct hydroxylation of benzene towards phenol with high conversion and selectivity remains a great challenge. We report herein an efficient La2CuO4 perovskite catalyst for one‐step oxidation of benzene using hydrogen peroxide under mild conditions. The catalyst was characterized using XRD, TEM, XPS, TG‐DTA, and other advanced techniques. The one‐pot hydroxylation reaction carried out at 60 °C under optimum reaction conditions in the presence of catalytic material shows benzene to phenol transformation with 51% conversion with >99% selectivity with 65 percent peroxide efficiency, respectively. The influence of reaction conditions such as temperature, amount of oxidant, reaction time and mode of addition of the oxidant was crucial in selectivity optimization. [ABSTRACT FROM AUTHOR]

Nano-sized bimetal Cu–Fe silica catalyst (Cu–Fe–SiO2/S) had been directly prepared by supercritical one-step method from sodium silicate to catalyze phenol hydroxylation. Compared with the ordinary silica, it had the same structure and composition with smaller particle size, more fluffy morphology and larger oil absorption. Its particle size mainly was 20 nm with 192.4 m2/g specific surface area, and much higher than that of ordinary silica (90.0 m2/g). This method employing bimetal Cu–Fe–SiO2/S as catalyst for phenol hydroxylation was better catalytic activity than Fe–SiO2/S and Fe-containing precipitated silica catalyst (Fe–SiO2/P), which was benefited the favorable performance attributes such as larger specific surface area and more regular pore structure as catalyst support, and the synergistic catalysis between Cu and Fe. Under optimal reaction conditions, 46.9% of dihydroxybenzene yield, 43.3% of catechol yield, 3.6% of hydroquinone yield, and 82.3% of catechol selectivity was achieved. The possible catalytic reaction mechanism for phenol hydroxylation over Cu–Fe–SiO2/S was also suggested. [ABSTRACT FROM AUTHOR]

The direct hydroxylation of benzene is a green and economical-efficient alternative to the existing cumene process for phenol production. However, the undesired phenol selectivity at high benzene conversion hinders its wide application. Here, we develop a one-pot synthesis of protonated g-C3N4 supporting vanadia catalysts (V-pg-C3N4) for the efficient and selective hydroxylation of benzene. Characterizations suggest that protonating g-C3N4 in diluted HCl can boost the generation of amino groups (NH/NH2) without changing the bulk structure. The content of surface amino groups, which determines the dispersion of vanadia, can be easily regulated by the amount of HCl added in the preparation. Increasing the content of surface amino groups benefits the dispersion of vanadia, which eventually leads to improved H2O2 activation and benzene hydroxylation. The optimal catalyst, V-pg-C3N4-0.46, achieves 60% benzene conversion and 99.7% phenol selectivity at 60 oC with H2O2 as the oxidant. [ABSTRACT FROM AUTHOR]

An enantioselective total synthesis of novel gingerol-related compound 4-((3S,5R)-3,5-dihydroxynonadecyl)phenol, an anti-oxidant isolated from the resinous exudates of Chilean desert plants, has been accomplished from a known commercially available 4-(but-3-enyl) phenol by a concise ten-step sequence. In this synthesis, Sharpless asymmetric dihydroxylation, Grignard reaction and Iodine-induced electrophilic cyclization have been applied as key steps. [ABSTRACT FROM AUTHOR]

Phenol is an important chemical material that is widely used in industry. Currently, phenol is dominantly produced by the well-known three-step cumene process, which suffers from severe drawbacks. Therefore, developing a green, sustainable, and economical strategy for the production of phenol directly from benzene is urgently needed. In recent years, the photocatalytic hydroxylation of benzene to phenol, which is economically feasible and could be performed under mild conditions, has attracted more attention, and development of highly efficient photocatalyst would be a key issue in this field. In this review, we systematically introduce the recent achievements of photocatalytic hydroxylation of benzene to phenol from 2015 to mid-2022, and various heterogeneous photocatalysts are comprehensively reviewed, including semiconductors, polyoxometalates (POMs), graphitic carbon nitride (g-C3N4), metal–organic frameworks (MOFs), carbon materials, and some other types of photocatalysts. Much effort is focused on the physical and chemical approaches for modification of these photocatalysts. The challenges and future promising directions for further enhancing the catalytic performances in photocatalytic hydroxylation of benzene are discussed in the end. [ABSTRACT FROM AUTHOR]

[Display omitted] • An electrophotochemical flow microreactor was designed and manufactured via 3D printing. • Continuous electrophotocatalytic C-H hydroxylation of benzene was investigated to enhance the phenol production. • The as-developed microreactor produces phenol more efficiently and stably than the batch counterpart. • Machine learning was employed to explore the importance of various parameters. 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. [ABSTRACT FROM AUTHOR]

Phenols are prominent in organic reactions and highly significant biologically active substances. We report a versatile and sustainable CuI-catalyzed protocol for their synthesis through an oxidative ipso-functionalization (hydroxy deborylation) strategy of (hetero)arylboronic acids [(H)ABAs] using the water extract of pomegranate peel ash (WEPA) in open-air. They are formed at room temperature (RT). This process shows high significance toward the environmental sustainability over the reported procedures of ipso-hydroxylation of (H)ABAs. The application of a waste-derived biorenewable basic reaction medium, air as an oxidant, wide substrate scope, high functional group tolerance, reusability of the catalyst, ambient conditions, less expensive and safer catalyst with low loading, aqueous medium, avoidance of volatile organic solvents, and external oxidant, and tremendous further scope are the noteworthy features of this protocol. [ABSTRACT FROM AUTHOR]

[Display omitted] Layered double hydroxides (LDHs) own admirable potential due to their controllable composition and exchangeable interlayer anions. Herein, pyrenetetrasulfonic acid (PTS) intercalated ZnAl-LDHs (denoted as ZnAl-xPTS, x represents the amount of NaPTS in the starting material) are synthesized by a co-precipitation method, which display enhanced photocatalytic activity towards the hydroxylation of phenylboric acid to phenol. Various characterizations suggest that PTS plays significant roles in improving the photocatalytic activity: (1) PTS extends the light absorption from ultraviolet to visible light region; (2) the introduction of PTS upshifts the conduction band, which is feasible for the formation of O 2 ∙-; (3) ZnAl-xPTS produces more free electrons under light irradiation, which leads to greatly improved activity. This study develops an alternative LDHs based photocatalyst for the production of phenol, which also provides an efficient strategy to improve the photocatalytic activity of LDHs. [ABSTRACT FROM AUTHOR]

The late stage photochemical hydroxylation of biaryl sulfonium salts was enabled with a TEMPO derivative as a simple oxygen source, in metal free conditions. The scope and mechanism of this exceptionally simple synthetic method, which constructs important arylated phenols from aromatic C–H bonds, are herein discussed. [ABSTRACT FROM AUTHOR]

Direct hydroxylation of benzene with a high selectivity and durability for phenol production is still a challenge. Herein, a reusable VxOy/AC(cit)-DBD catalyst was synthesized using a facile and environmentally benign method in which a mixture of citric acid, NH4VO3 and activated carbon (AC) was treated using dielectric barrier discharge (DBD) at room temperature and under an N2 atmosphere. Compared with VxOy/AC-DBD, which is prepared without citric acid, more vanadium species were exposed on the surface of VxOy/AC(cit)-DBD. The residues of citric acid formed by DBD treatment can stabilize the vanadium species on the surface of AC by restraining the leaching of vanadium from the catalyst during the reaction. Moreover, the addition of citric acid increased the ratio of V4+/V5+ and benzene adsorption on the catalyst surface, which are favorable for the hydroxylation of benzene. Additionally, the resulting vanadium particles are smaller (less than 10 nm) and amorphous owing to the inhibiting effect of citric acid residues on particle growth and the low temperature characteristics of DBD treatment. Under the optimized reaction conditions, VxOy/AC(cit)-DBD showed a good stability and recyclability in the hydroxylation of benzene and achieved a benzene conversion of 21.5% and phenol selectivity of 99.1%. [ABSTRACT FROM AUTHOR]

One-step selectively photocatalytic phenol hydroxylation to produce Dihydroxybenzenes (DHB) is an attractive and challenging strategy. However, the rapid recombination of photogenerated carriers existed in single component photocatalyst seriously hinders the photocatalytic efficiency. The heterojunction strategy can optimize the band structure of the photocatalyst, and effectively improve the carriers' separation and transfer during the photocatalytic process. Herein, we successfully designed and prepared a 3D TiO 2 @Ni 3 Fe 1 -LDH core-shell heterostructure photocatalyst by coupling TiO 2 nanorods with Ni 3 Fe 1 -LDH nanosheets for the photocatalytic phenol hydroxylation to produce DHB. The results showed that the 3D TiO 2 @Ni 3 Fe 1 -LDH core-shell heterostructure had a suitable energy band structure for the photocatalytic phenol hydroxylation and the heterostructure accelerated the carriers' separation and transfer. Meanwhile, the high porosity and abundant active sites were conducive to the adsorption of H 2 O 2 and the photogenerated carriers transfer efficiency from the photocatalyst to H 2 O 2. The 3D TiO 2 @Ni 3 Fe 1 -LDH core-shell heterostructure showed excellent photocatalytic performance of phenol hydroxylation, where the phenol conversion was 48.6%, and the selectivity of DHB was 81.1% at 25 °C and 4 h of light illumination. Furthermore, the as-prepared photocatalysts exhibited good stability after four cycles of experiment. This work provided a convenient and efficient method for the green synthesis of DHB. 3D TiO 2 @NiFe-LDH core-shell heterostructures photocatalysts were fabricated by coupling anatase TiO 2 nanorods with NiFe-LDH nanosheets. The 3D TiO 2 @NiFe-LDH core-shell heterostructures with a suitable energy band structure for the photocatalytic phenol hydroxylation and the heterostructure accelerates the carrier separation rate showed excellent photocatalytic performance of phenol hydroxylation. [Display omitted] • 3D TiO 2 @NiFe-LDH core-shell heterostructures were fabricated. • Core-shell heterostructures accelerated photogenerated carriers' separation and transfer. • Uniformly growth of LDHs improved conductivity and light absorption of the photocatalyst. • TiO 2 @Ni 3 Fe 1 -LDH performed well in selectively photocatalytic phenol hydroxylation. • The photocatalytic phenol hydroxylation followed the mechanism dominated by.•OH species. [ABSTRACT FROM AUTHOR]

Phenols are important components of pharmaceuticals, biologically active natural products, and materials. Here, we briefly discuss recent advances in catalytic hydroxylation reactions for the synthesis of phenols, with particular attention to our recent work. H2 O is proved to be an efficient hydroxide reagent in converting (hetero)aryl halides into the corresponding phenols under synergistic organophotoredox and nickel catalysis. Aryl bromides as well as less reactive aryl chlorides show high reactivity in this catalytic system. This methodology can be applied to the efficient synthesis of diverse phenols and allows the hydroxylation of multifunctional pharmaceutically relevant aryl halides. 1 Introduction 2 Representative Methods for Transition-Metal-Catalyzed Hydroxylation of (Hetero)Aryl Halides 3 Organophotoredox/Ni Dual Catalytic Hydroxylation of Aryl Halides with Water 4 Summary and Outlook [ABSTRACT FROM AUTHOR]

Herein, we report the first decarboxylative hydroxylation to synthesize phenols from benzoic acids at 35 °C via photoinduced ligand‐to‐metal charge transfer (LMCT)‐enabled radical decarboxylative carbometalation. The aromatic decarboxylative hydroxylation is synthetically promising due to its mild conditions, broad substrate scope, and late‐stage applications. [ABSTRACT FROM AUTHOR]

Herein, we report the first decarboxylative hydroxylation to synthesize phenols from benzoic acids at 35 °C via photoinduced ligand‐to‐metal charge transfer (LMCT)‐enabled radical decarboxylative carbometalation. The aromatic decarboxylative hydroxylation is synthetically promising due to its mild conditions, broad substrate scope, and late‐stage applications. [ABSTRACT FROM AUTHOR]

Using MOF-5 as a template, the porous carbon (MDPC-600) possessing high specific surface area was obtained after carbonization and acid washing. After MDPC-600 was loaded with Cu ions, the catalyst Cu/MDPC-600 was acquired by heat treatment under nitrogen atmosphere. The catalyst was characterized by X-ray powder diffraction (XRD), N2 physical adsorption (BET), field emission electron microscope (SEM), energy spectrum, and transmission electron microscope (TEM). The results show that the Cu/MDPC-600 catalyst prepared by using MOF-5 as the template has a very high specific surface area, and Cu is uniformly supported on the carrier. The catalytic hydrogen peroxide oxidation reaction of phenol hydroxylation was investigated and exhibits better catalytic activity and stability in the phenol hydroxylation reaction. The catalytic effect was best when the reaction temperature was 80°C, the reaction time was 2 h, and the amount of catalyst was 0.05 g. The conversion rate of phenol was 47.6%; the yield and selectivity of catechol were 37.8% and 79.4%, respectively. The activity of the catalyst changes little after three cycles of use. [ABSTRACT FROM AUTHOR]

Visible‐light‐driven organic reactions are environmentally friendly green chemical transformations among which photosynthetic oxidative hydroxylation of arylboronic acids to phenols has attracted increasing research interest during the very recent years. Given the efficiency and reusability of heterogeneous catalysts, COF‐JLU25, an electron‐rich COF‐based photocatalyst constructed by integrating electron‐donating blocks 1,3,6,8‐tetrakis(4‐aminophenyl)pyrene (PyTA) and 4‐[4‐(4‐formylmethyl)‐2,5‐dimethoxyphenyl] benzaldehyde (TpDA), was selected as a photocatalyst for the oxidative hydroxylation of arylboronic acids. In our studies, COF‐JLU25 demonstrated excellent photocatalytic activity with high efficiency, robust reusability, and low catalyst loading, showcasing an application potential of previously underexplored COF‐based photocatalyst composed solely of electron‐rich units. [ABSTRACT FROM AUTHOR]

A V2O5@TiO2 catalyzed green and efficient protocol for the hydroxylation of boronic acid into phenol has been developed utilizing environmentally benign oxidant hydrogen peroxide. A wide range of electron‐donating and the electron‐withdrawing group‐containing (hetero)aryl boronic acids were transformed into their corresponding phenol. The methodology was also applied successfully to transform various natural and bioactive molecules like tocopherol, amino acids, cinchonidine, vasicinone, menthol, and pharmaceuticals such as ciprofloxacin, ibuprofen, and paracetamol. The other feature of the methodology includes gram‐scale synthetic applicability, recyclability, and short reaction time. [ABSTRACT FROM AUTHOR]

Nano-size titanium silicalites is difficult to be separate from the reaction solution, lamellar and homogeneous Ti-MWW zeolites are successfully formed a dense zeolite layers on α-Al 2 O 3 pellets by secondary hydrothermal synthesis in this study. Seeded crystals concentration and titanium source have significantly influences on the morphology, thickness and titanium active sites of Ti-MWW zeolites. Doping NH 4 F in the precursor synthesis solution could conducive to prepare macroscopically and anatase-free Ti-MWW zeolites layer on the outside of α-Al 2 O 3 pellets, and the thickness of the Ti-MWW zeolites layer is ca. 1 mm. Besides, catalytic performance of the supported Ti-MWW zeolites are significantly improved by NH 4 F. A fixed-bed reactor with the supported Ti-MWW zeolites are applied to catalyze phenol hydroxylation with hydrogen peroxide efficiently, and reaction time and temperature, amount of the supported Ti-MWW zeolites have obvious effects on the phenol conversion and dihydroxybenzene selectivity. When the actual mass of Ti-MWW zeolites to volume of reaction solution is only 10 g/L, the relative phenol conversion and dihydroxybenzene selectivity are 46.45% and 92.72% at 65 °C after 3 h, respectively. [Display omitted] • Lamellar and homogeneous Ti-MWW zeolites form a dense layers on α-Al 2 O 3 pellets by secondary hydrothermal synthesis. • NH 4 F could conducive to prepare the macroscopically and anatase-free Ti-MWW zeolites layer. • A fixed-bed reactor filled with the loaded Ti-MWW zeolites are applied to catalyze phenol hydroxylation. • Phenol conversion and dihydroxybenzene selectivity are 46.45% and 92.72% with low catalyst dosage (10 g/L). [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr-MgO/Bi 2 O 3 nanocomposites were synthesized for the first time and evaluated for the photocatalytic hydroxylation of benzene to phenol. • The syntheized 10% Cr-MgO/Bi 2 O 3 composite exhibited remarkably enhanced photocatalytic performance compared with bare Bi 2 O 3 , MgO and MgO/Bi 2 O 3. • The conduction of heterojunction between Bi 2 O 3 and MgO, coupled with the generation of a new trapping level within Cr-MgO/Bi 2 O 3 by Cr doping contribute to the enhanced photocatalytic performance. A series of Cr-doped MgO/Bi 2 O 3 (Cr-MgO/Bi 2 O 3) nanocomposites were prepared for the photocatalytic benzene hydroxylation to produce phenol by the visible-light exposure, and the catalyst dosage, solvents and volume ratio of benzene to H 2 O 2 were thoroughly examined. The well-characterized photocatalyst (10% Cr- MgO/Bi 2 O 3) by various physico-chemical and spectroscopic techniques was found to be highly efficient with an optimal phenol selectivity of 98.5% and yield of 13.8%, which were much higher than those obtained from bare Bi 2 O 3 , MgO and MgO/Bi 2 O 3. The remarkably improved photocatalytic activity was resulted from the conduction of heterojunction between Bi 2 O 3 and MgO, as well as the generation of a new trapping level within Cr-MgO/Bi 2 O 3 by Cr doping, which greatly accelerated the photogenerated charge carriers separation. This work combining heterojunction conduction and transition metal doping exhibits promising potential for future applications in organic transformation reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single VO 4 sites were constructed on hydrophobic poly(ionic liquid)-derivative. • Combination of ion-exchange and pyrolysis caused the formation of V(IV) species. • The stability and hydrophobicity of the catalyst were enhanced after pyrolysis. • The catalyst was efficient in the H 2 O 2 -mediated benzene hydroxylation to phenol. • High H 2 O 2 utilization efficiency > 90 % was reached with large TOF above 900 h−1. Hydrogen peroxide (H 2 O 2)-mediated benzene hydroxylation is one of the most attractive avenues towards green synthesis of phenol, a crucial industrial feedstock. Nonetheless, it remains one challenge to explore efficient catalysts, especially the one allowing high H 2 O 2 utilization efficiency to fulfill the safety production. In this work, isolated single VO 4 sites were constructed on the hydrophobic poly(ionic liquid)-derivative through copolymerization of dinuclear imidazolyl ionic liquid and polyhedral oligomeric silsesquioxane (POSS), ion change with ammonium metavanadate (NH 4 VO 3), and the pyrolysis under moderate temperature. The combination of V(IV) single sites and a hydrophobic surface made the catalyst effectively catalyzing the phenol synthesis from benzene oxidation with H 2 O 2 , giving phenol selectivity above 99 %, H 2 O 2 utilization efficiency of 92 %, and turnover frequency (TOF) beyond 900 h−1. The catalyst was stably recycled and exhibited broad substrate compatibility. The pyrolysis step strengthened both stability and activity, significantly contributing to the high catalytic efficiency. [ABSTRACT FROM AUTHOR]

Good inter-grown TS-2 zeolites layer is successfully prepared on the outer surface of porous millimeter α-Al 2 O 3 sphere by secondary hydrothermal synthesis. The supported TS-2 zeolites are loaded into a fixed-bed catalytic reactor for catalyzing phenol hydroxylation by hydrogen peroxide, which could efficiently avoid the fussy separation process. Influences of synthesis parameters on Ti active micro-environment, crystal morphology and catalytic performance of the supported TS-2 zeolites are investigated in this work, medium isopropanol content is necessary for preparing fine and homogenous TS-2 zeolites layer on the porous α-Al 2 O 3 sphere. Besides, formation process of the supported TS-2 zeolites is studied in this study, which divided into three stages, dissolution of seed crystals, formation of novel nuclei, growth and aggregation of TS-2 zeolites layer. When the titanium source, isopropanol/SiO 2 and TiO 2 /SiO 2 molar ratio of the initial synthesis gel are tetrabutyl titanate, 1.0 and 0.035, tetra-coordinated titanium containing and compact TS-2 zeolites layer are fully covered on the α-Al 2 O 3 sphere, the optimum phenol conversion and dihydroxybenzene selectivity of the zeolites are 40.07% and 98.52% at 65 °C. [Display omitted] • Good inter-grown TS-2 zeolites layer is successfully prepared on the outer surface of the millimeter α-Al 2 O 3 sphere. • Medium IPA/SiO 2 ratio is favor for preparing high tetra coordinated titanium, homogeneous and fine TS-2 zeolites layer. • The optimum titanium source and TiO 2 /SiO 2 molar ratio of the initial synthesis gel are TBOT and 0.035. • Supported TS-2 zeolites are loaded into the fixed-bed catalytic reactor and present a good catalytic performance for phenol hydroxylation. • The maximum phenol conversion and hydroquinone selectivity are 40.07% and 98.52% at 50 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple metal-free strategy for the synthesis of phenols. • An azopyrazole-linked Schiff base as organocatalyst. • Use of the green solvent system for the synthesis. A simple metal-free strategy for the synthesis of phenols from aryl and hetero aryl-boronic acids using arylazopyrazole linked o -hydroxyl Schiff base has been illustrated. These sustainable ipso -hydroxylations have very short reaction times, using aqueous H 2 O 2 as the oxidant in aqueous-alcoholic medium. The current protocol has been demonstrated to be effective with a variety of electron-rich and electron-deficient aromatic substrates and provides access to a wide range of phenols. This is the first time that an azoyrazole linked Schiff base has been used to increase the nucleophilicity of H 2 O 2 , in oxidative hydroxylation reactions. [ABSTRACT FROM AUTHOR]

The selective oxidation of phenol into cis, cis -muconic acid was carried out with α-zirconium phosphate supported-copper catalysts. It has been found that a sole α-zirconium phosphate exhibited a preferential selectivity (up to 80%) towards dihydroxybenzene (Catechol/Hydroquinone=1.4:1). Moreover, the further studies indicated that α-zirconium phosphate-supported copper catalysts enable to catalyze the oxidative cleavage of catechol into high-added valuable platform molecule cis,cis -muconic acid (ccMA) by in-situ generating performic acid. A 66% conversion of phenol and 60% selectivity towards cis, cis -muconic acid were obtained under mild reaction condition (30 °C, 2 h). The detailed characterization by means of XRD, SEM, TEM, and pyridine-absorbed FT-IR techniques demonstrated that copper(II) species were highly dispersed on α-zirconium phosphate, and could be bonded with the phosphate group of the support. The forming Cu(II)-O-P linkage was proved to be catalytically active species and endowed the supported-copper catalysts with a superior recyclability. The reaction pathway involved hydroxylation of phenol to give a mixture of catechol (CL) and hydroquinone (HQ), followed by the formation of a metal-catechol complex which was then rapidly oxidized into cis, cis -muconic acid (ccMA). [Display omitted] • Zirconium phosphate supported Cu(II) catalyst have been constructed. • The catalysts show superior performance for the oxidation of phenol to cis, cis- muconic acid. • There is the strong coordination between Cu(II) species and phosphate group of α-ZrP. • The forming Cu(II)-O-P linkage was active sites for the selective oxidation of phenol. • The interaction endows the supported Cu(II) catalysts with outstanding recyclability. [ABSTRACT FROM AUTHOR]

In this study, Cr-doped CdS/ZnO (Cr-CdS/ZnO) nanocomposites were synthesized for the first time and systematically characterized using different physicochemical methods, such as XRD, SEM, HRTEM, UV-Vis DRS, XPS, PL, EIS and EPR, etc. The photocatalytic activity of the Cr-CdS/ZnO nanocomposites was evaluated for the hydroxylation of benzene to phenol using H 2 O 2 as the oxidant under visible-light irradiation. The impacts of various reaction conditions, including the role of catalyst dosage, solvents and volume ratio of benzene to H 2 O 2 were specifically investigated. Owing to the similar lattice structure and well-matched band positions of CdS and ZnO, generation of electrons and holes by CdS-captured photons, as well as separation and imigration of electrons to ZnO were all realized. Furthermore, Cr-doping favored the formation of a new trapping level in the band gap of the Cr-CdS/ZnO composite, which would not only enhance visible-light absorption capacity, but also inhibit the rapid recombination of photo-generated electron-hole pairs. As a result, an excellent phenol selectivity of 98% with a phenol yield of 11.1% was achieved, which was higher than those of the pristine Cr-CdS, Cr-ZnO and CdS/ZnO. In the end, a rational mechanism for enhanced photocatalytic activity of the synthesized composites under visible-light irradiation was also proposed. The visible-light absorption and remarkably improved photocatalytic performance for benzene hydroxylation enable the potential of Cr-CdS/ZnO nanocomposites for the application of photocatalytic green synthesis of fine chemicals. [Display omitted] ● Cr-CdS/ZnO was synthesized for the first time and evaluated for the photocatalytic hydroxylation of benzene to phenol. ● The introduction of Cr favored the formation of a new trapping level in the band gap of the Cr-CdS/ZnO composites. ● 5% Cr-CdS/ZnO exhibited remarkably enhanced photocatalytic performance compared with the pristine Cr-CdS, Cr-ZnO and CdS/ZnO. [ABSTRACT FROM AUTHOR]

Direct synthesis of phenol from benzene in the presence of water and oxygen were conducted under visible-light irradiation. Effects of several noble metal co-catalyst on the selective hydroxylation of benzene over WO 3 photocatalysts have been extensively studied. The photocatalytic activities of WO 3 for phenol formation strongly depend on co-catalyst such as Pt, Au, Pd metal species, i.e., phenol formation was as follows: Pt-WO 3 > Au-WO 3 > Pd-WO 3. Furthermore, the WO 3 photocatalyst deposited bimetal co-catalysts such as Pd/Pt, Pd/Au and Pt/Au were also investigated. The Pd/Pt-WO 3 photocatalyst was found to show the highest photocatalytic activity for phenol formation due to an effective oxygen reduction reaction (ORR) for bimetallic Pd/Pt cocatalyst. From the experimental and theoretical studies, phenol was confirmed to form by the insertion of OH derived from H 2 O into benzene, and simultaneous cleavage of benzylic carbon-hydrogen bond (C sp2 -H) by an assist of co-catalyst surface through the push-pull process. [Display omitted] • Benzene was hydroxylated to form phenol on the WO 3 photocatalyst. • Noble metal cocatalysts deposited on the WO 3 photocatalysts was investigated. • Pd/Pt-WO 3 exhibited the highest photocatalytic activity for phenol formation. • Phenol was formed by the insertion of OH through the push-pull mechanisms. • Pd/Pt co-catalyst exhibited liberation of surface OH species more easily than Pt. [ABSTRACT FROM AUTHOR]

Evolution of fluorometric sensing methods has brought an enormous opportunity and exhibited novel potentials for enzymatic activities determination. Herein, we have established an accurate and straightforward fluorescent sensing approach for tyrosinase (TYR) activity based on the formation of fluorescent silicon nanoparticles (Si NPs). Influenced by TYR-induced hydroxylation of phenol into catechol, and an easy reaction between catechol and 3(2-aminoethylamino) propyl (dimethoxymethylsilane) (AEAPDMMS) to generate Si NPs, we have designed a label-free fluorescence turn-on probe for TYR activity measurement. After optimization of all reaction parameters, the proposed approach could selectively determine TYR activity in the linearity range of 0.08–9 U mL−1 with the limit of detection (LOD) of 0.03 U mL−1. The practicability of the method in real sample was assessed by measuring TYR activity in human serum sample with successful results. In addition, Si NPs were wonderfully acceptable for Hela and SiHa cells imaging by virtue of their tolerable cytotoxicity and impressive biocompatibility. Therefore, the designed fluorescent biosensor exhibited a potential and widespread implementation in clinical diagnoses assays. • Silicon nanoparticles based-fluorescence probe was used to determine Tyrosinase. • Tyrosinase could easily make hydroxylation of phenol into catechol. • No further surface modification or purification of silicon nanoparticles was applied. • The designed approach exhibited high performance for Hela and SiHa cell imaging capability. • The designed method was used to determine Tyrosinase in human serum samples. [ABSTRACT FROM AUTHOR]

In this work, the photocatalytic hydroxylation of benzene to phenol in presence of H 2 O 2 is studied using, for the first time, a photoreactive polymer composite based on N-doped TiO 2 (N-TiO 2) embedded into a monolithic syndiotactic polystyrene aerogel (N-TiO 2 /sPS, 10/90 w/w). N-TiO 2 /sPS is able to enhance the phenol selectivity and yield compared to bare N-TiO 2. The best results in terms of selectivity (98%) and phenol yield (57%) are achieved under visible light in acidic conditions (pH=2), preserving a high benzene conversion (58%). In addition, N-TiO 2 /sPS is recovered from the aqueous solution containing the reaction products and reused several times without significant loss of photoreactivity and reduction of phenol yield. The described photoreactive solid phase represents a "proof of concept" that could allow a significant leap forward in the development of innovative green processes for the selective oxidation of aromatic hydrocarbons under mild conditions. [Display omitted] • A photoreactive solid phase (PSP) active under UV and visible light is synthesized. • PSP is based on N-doped TiO 2 embedded into syndiotactic polystyrene aerogel • Selective photocatalytic oxidation of benzene to phenol is achieved • The selectivity and phenol yield markedly increased in presence of PSP • PSP can be an efficient photocatalyst for benzene hydroxylation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Radiolytic yields reflect the charge distribution in the aromatic rings of HBPs. • The OH mostly adds to the ortho and para positions of the phenol in HBPs. • Concerted effects of –OH and –benzyl groups in the reaction of OH with HBPs. • Relative partial yields for the addition of OH to hydroxybiphenyls. Studies on the distribution of products in radiolytic hydroxylation of hydroxybiphenyls (HBPs) to obtain information on the concerted effect of substituent groups at the OH addition site have been conducted. Liquid chromatography was used to analyze the radiolytic products. Results show that OH is selectively added to the free positions of aromatic rings and the directing effect of the substituents was –OH > phenol > phenyl. The yields of each product are provided; these reflect the charge distribution in the HBP, such that the phenyl ring modified the ortho - para directing effect of the –OH substituent. The ratio of addition of the OH to the HBPs obtained provide a quantitative basis for considering the effect of substituents in determining the site of OH attack on these compounds and provides additional valuable data on the attack of the OH for studies on the degradation of aromatic compounds present in polluted waters. [ABSTRACT FROM AUTHOR]

• Remarkable characteristics of mesoporous Fe 2 O 3 -TiO 2 mixed oxides were studied. • Fe-loading influenced the acidic property of the catalyst. • The acidic property of the catalyst plays a predominant role in the selective hydroxylation of benzene. The omnipresence of C H bonds in organic molecules enamors chemists for the functionalization of C H bonds towards value-added molecular scaffolds. Mesoporous Fe 2 O 3 -TiO 2 mix-oxide catalyst has been successfully synthesized via a triblock-copolymer (P123) mediated sol-gel method and catalytically tested in selective hydroxylation of benzene. The as-synthesized catalysts were comprehensively characterized by powder XRD, Raman spectroscopy, FT-IR, N 2 -physisorption, FESEM, HRTEM, XPS, and NH 3 -TPD techniques. The physicochemical characterizations evidence that Fe(III) ions incorporate into the pure anatase TiO 2 lattice framework and the crystallite size decreases as iron concentration increases. The XPS analyses confirm the Fe3+ state (BE 710.3 eV) in Fe-O-Ti with a peak at 712.1 eV for Fe3+ of Fe 2 O 3. The NH 3 -TPD results show that the 5 wt% Fe-TiO 2 has a higher total acidity of 105 µmol/g. Interestingly, a further increase in iron amount decreases the total acidity. Herein, we observe that the surface acidity directs the selectivity towards phenol. The effect of different reaction parameters was carefully investigated. Under the optimized conditions, 5% Fe-TiO 2 with notified strong acid sites gives a higher phenol yield of 31.2% with > 99% selectivity; moreover, the catalyst is reusable at least four times. C H activation of benzene over mesoporous Fe 2 O 3 -TiO 2 mixed oxide synthesized by conventional sol-gel method [Display omitted] [ABSTRACT FROM AUTHOR]

• Hydroxylation reaction is an important organic transformation which produces value-added products. In biological systems, hydroxylation reactions of organic molecules are usually carried out by enzymes. There are catalytic and non-catalytic techniques used for introducing the OH group into an organic molecule. In the catalytic approach, transition-metal-catalyzed hydroxylation is an important strategy which has attracted a lot of attention. The production of phenol and other pharmacologically active compounds is now easily possible through transition metal-catalyzed hydroxylation. However, Palladium, Rhodium, and other noble transition metal catalysts are not environmentally benign. Thus, here we compiled a review on the recent advances in the hydroxylation process using non-noble transition metals such as Nickel, Iron, Copper, and manganese catalysts for the synthesis of phenol and other pharmacologically active compounds covering literature from 1980 to 2021. For simplicity and better understanding, the topic has been classified based on the type of bond which has undergone hydroxylation such as the C H, C-X and C-B.. • Since the theme of the review falls within the scope of J. Organomet. Chem. we would like to submit the manuscript for publication in J. Organomet. Chem. We strongly believe that the review will attract the attention of a large volume of organic chemists, catalysis researchers and medicinal chemists. We request you to kindly consider the manuscript for publication in J. Organomet. Chem. Hydroxylation reactions are a type of chemical transformation in which OH functionality is introduced into organic substrates. Hydroxylation processes are usually catalyzed by enzymes like ω-hydroxylase and cytochrome P 450 , which are prevalent in nature and human body. There are catalytic and non-catalytic techniques used for introducing the OH group into an organic molecule. In the catalytic approach, transition-metal-catalyzed hydroxylation is an important strategy which has attracted a lot of attention. The production of phenol and other pharmacologically active compounds is now easily possible through transition metal-catalyzed hydroxylation. However, Palladium (Pd), Rhodium (Rh), and other noble transition metal catalysts are not environmentally benign. Here we compiled the reports regarding non-noble transition metals such as Nickel (Ni), Iron (Fe), Copper (Cu), and Manganese (Mn) catalysts for hydroxylation reactions to synthesize phenol and other pharmacologically active compounds with high yield, economy, and environmental friendliness. This review covers literature from 1980 to 2021. [Display omitted] [ABSTRACT FROM AUTHOR]

• A hydrothermal carbon with oxygen groups and polyfuran units was constructed. • The catalyst was efficient in metal-additive-free oxygen-mediated benzene to phenol. • Surface oxygen groups as the active sites to form ·OH radials to oxidize benzene. • The polyfuran units promoted the O 2 adsorption and activation to accelerate reaction. Direct benzene hydroxylation with dioxygen (O 2) is among the most promising alternative pathways for green phenol production, but efficient catalysis systems usually involve metal species or other additives such as sacrificial agents. In this work, we designed a carbon catalyst from the hydrothermal treatment of biomass-derived sucrose and constructed a metal-/additive free heterogeneous catalytic system for benzene hydroxylation to phenol with O 2. The champion carbon sample gave a high phenol yield of 13.4%. The catalyst was facilely recovered and reused without apparent deactivation. There abundant oxygen functional groups such as phenolic and quinone carbonyl groups served as the active sites and polyfuran units accelerated the O 2 adsorption and activation. The synergistic effect of these surficial organic groups is conducive to the formation of reactive oxygen species, hydroxyl radicals, which effectively oxidized the benzene to phenol. Sucrose-derived hydrothermal carbon material with abundant polyfuran units allowed the efficient metal- and additive-free benzene hydroxylation to phenol with O 2. [Display omitted] [ABSTRACT FROM AUTHOR]

• Direct hydroxylation of arenes to phenols was reported. • A copper(II) complex of an N4 aminobenzimidazole was used as an efficient catalyst. • Hydrogen peroxide was used as a green oxidant. Direct hydroxylation of arenes to phenols with hydrogen peroxide as a green oxidant is an attractive approach. In the present study, we prepared several copper (II) complexes bearing tetra- (N4), tri- (N3) and pentadentate (N5) ligands, and the copperII-N4 complex could act as an efficient catalyst for hydroxylation of benzenes with H 2 O 2 (up to 22.4% yield of phenols with 10.0 equiv. H 2 O 2 , and 38.0% yield of phenol with limited amount of H 2 O 2) at room temperature. X-ray crystallographic analysis indicates that the CuII-N4 complex exhibits a square-pyramidal geometry and that two methyl groups connecting to the diamine are cis to each other. In comparison, copper(II) complexes supported by tri- (N3) and pentadentate (N5) ligands were also evaluated in the hydroxylation of benzene, demonstrating inferior performance. [Display omitted]. [ABSTRACT FROM AUTHOR]

Aerobic hydroxylation of phenylboronic acids to phenols has attracted considerable attention but is exceedingly challenging due to the obstacle in the activation of oxygen (O 2). Here, two carbazole-based conjugated microporous polymers (CMPs), namely TCB-CMP and EFC-CMP, were fabricated through polymerization of 1,3,5-tri(9 H -carbazole-9-yl)benzene (TCB) and 9,9′-(9,9-diethyl-9 H -fluorene-2,7-diyl)bis(9 H -carbazole) (EFC), respectively. Gratifyingly, with N,N' -diisopropylethylamine (DIPEA) as the hole (h+) quencher, blue light photocatalysis of both carbazole-based CMPs could execute the aerobic hydroxylation of phenylboronic acids in ethanol (C 2 H 5 OH). Importantly, the EFC-CMP imparted superior photocatalytic activity to TCB-CMP due to the favorable reduction of O 2 to superoxide anion (O 2 •–) by electron (e–). Thereby, O 2 •– conducted the highly selective aerobic hydroxylation of phenylboronic acids. The aerobic hydroxylation of a wide range of phenylboronic acids to corresponding phenols was achieved with high yields. The work further demonstrates the feasibility of taming the oxidation potential of CMPs in producing delicate products like phenols. Blue light photocatalytic aerobic hydroxylation of phenylboronic acids to phenols has been completed promptly over carbazole-based conjugated microporous polymers. [Display omitted] • Two carbazole-based CMPs, namely TCB-CMP and EFC-CMP, are fabricated. • The e– from carbazole activates O 2 to O 2 •– to execute the aerobic hydroxylation. • Carbazole acts as Lewis base to close the distance with phenylboronic acids. • The superior photocatalytic activity of EFC-CMP is due to the favorable reduction of O 2. • The overoxidation of functionalized phenols is circumvented by h+ quenching. [ABSTRACT FROM AUTHOR]

A bulky composite material, CaCO 3 @TS-1, was synthesized in a tetrapropylammonium bromide hydrothermal system by adding nanosized CaCO 3 particles of 60–80 nm to a titanium silicalite-1 (TS-1) synthesis gel. The macroporous TS-1 free of extraframework Ti was then obtained by the posttreatment of the CaCO 3 @TS-1 in HCl solution to remove CaCO 3 and extraframework Ti simultaneously. This study demonstrates that this new synthesis route, the acidity posttreatment, can produce a bulky TS-1 with volume-controllable intracrystal macropores. The crystallization mechanism of the macroporous TS-1 was studied systematically. The addition of CaCO 3 accelerates the crystallization of silicon source, and leads to the similar crystallization rates of silicon and titanium sources. Therefore, the formation of extraframework Ti was inhibited, and more Ti ions were inserted into the TS-1 framework. The catalytic performance of macroporous TS-1 was evaluated in the hydroxylation of phenol. An outstanding catalytic activity was obtained due to their enhanced diffusion property and reduced extraframework Ti. [Display omitted] • Bulky macroporous TS-1 free of extraframework Ti was obtained by acidity treatment. • The macroporous volume can be controlled by tuning the CaCO 3 adding amount. • The addition of CaCO 3 accelerates the crystallization of silicon source. • An outstanding activity for phenol hydroxylation was obtained on macroporous TS-1. [ABSTRACT FROM AUTHOR]

Hydroxylation of benzene to phenol over a photocatalyst is a green approach toward phenol production. ZnFe 2 O 4 (ZFO) with an intrinsic peroxidase-like catalytic behavior toward H 2 O 2 activation is an emerging photocatalyst for benzene hydroxylation reaction; however, its catalytic performance is greatly limited by the fast charge recombination, inevitable metal leaching and hydrophilic surface structure. Herein, the encapsulation of ZFO by carbons (ZFO@C) is an effective solution to address these issues. The carbons conformably coating on ZFO not only protect them from corrosion and metal leaching, but also enable the generation of a strong electronic contact between them to facilitate charge separation. In addition, the carbons also increase the surface affinity for benzene adsorption. As a result, ZFO@C exhibited a significant enhanced photocatalytic activity and durability for phenol synthesis. Furthermore, ZFO@C with carbon derived unique functionalities will have a broad application in photocatalytic green synthesis of fine chemicals. [Display omitted] • Carbon encapsulated ZnFe2O4（ZFO@C）core-shell nanostructures are synthesized. • Carbon shells intimate adhering on ZFO surface are beneficial for charge separation. • The conformable encapsulation of ZFO by carbon shells suppresses metal leaching. • The carbon shells with hydrophobic surface and π -conjugated electron system favor for benzene adsorption. • ZFO@C exhibits a significant enhanced photocatalytic activity and durability for phenol synthesis. [ABSTRACT FROM AUTHOR]

Carbon encapsulated iron catalysts hold great potential for one-step hydroxylation of benzene to phenol due to their unique core-shell nanostructures. However, their catalytic performance is moderate, since the carbon shells have impeded their activity toward H 2 O 2 activation. Herein, we demonstrate that alloying engineering of Fe cores with Co atoms is a promising strategy to address the issue about H 2 O 2 activation. The incorporation of Co into Fe cores can generate strong synergetic effects to promote H 2 O 2 activation, while still maintaining the structural benefits of carbon shells for benzene hydroxylation reaction. As a result, the phenol yield obtained on carbon encapsulated FeCo (FeCo@C) reaches to 26.4 ± 0.7% with a selectivity of 96.2 ± 1.2%, much higher than that of Fe@C and Co@C. With the improved intrinsic catalytic behavior toward H 2 O 2 activation and well-reserved carbon structure benefits, FeCo@C should be a promising catalyst for a broad liquid-phase reactions using H 2 O 2 as the oxidant. [Display omitted] ● Co atoms were alloyed with encapsulated Fe cores to form FeCo@C core-shell nanostructures. ● FeCo@C exhibits strong synergetic effects to promote H 2 O 2 activation. ● FeCo@C reserves the structural benefits of carbon shells for benzene hydroxylation reaction. ● FeCo@C exhibits enhanced catalytic activity and robust durability for phenol synthesis. [ABSTRACT FROM AUTHOR]

The focus of this work is to use fly ash, a waste generated by thermal power plants, to synthesize an economical and efficient heterogeneous catalyst for the fine chemicals industry. To achieve this goal, fly ash zeolite (FAZ) was prepared from fly ash and Cu(II), Ni(II) and Co(II) complexes of 4-hydroxy-3-methoxybenzaldehyde [M(VAN)-FAZ] were loaded in the channels of zeolite matrix by flexible ligand strategy. The prepared FAZ was characterized by XRD, SEM, FT-IR, TGA, XRF and BET analyses. Encapsulation of metal complexes in zeolite gains the advantage of heterogeneity thereby facilitating easy separation of products and selectivity. The incorporation of metal complexes in the framework of FAZ was further assured by FT-IR, XRD, TGA, AAS and UV–Visible analyses of M(VAN)-FAZ. Thermographs indicated a loading of 6.70–16.09% of the metal complexes in FAZ. The –OH stretching reported at 3184 cm−1 for the free ligand was absent in the FT-IR spectra of the encapsulated metal complexes, indicating the binding of this group with the metal ion. The loading of metal complexes in the pores of FAZ have been further confirmed by AAS reports. The FAZ encapsulated transition metal complexes of vanillin have been established as catalysts for phenol hydroxylation. The extent of phenol conversion increased with time, after 240 min, 90% phenol conversion was observed and the preferential catalytic activity of [M(VAN)-FAZ] was observed as: [Cu(II)(VAN)-FAZ] > [Co(II)(VAN)-FAZ] > [Ni(II)(VAN)-FAZ]. The products were characterized by GC-MS analysis and the recyclability of the prepared catalyst was assessed up to three cycles. • Fly ash is a waste material generated by thermal power plants, which is hazardous when dumped in land. • Conversion of fly ash to fly ash-based zeolite, offers a low-cost substitute for commercial zeolites. • Encapsulation of transition metal complexes of 4-Hydroxy-3-methoxybenzaldehyde in fly ash based zeolite suggests a catalyst for hydroxylation of phenol with excellent recyclability up to three cycles. [ABSTRACT FROM AUTHOR]

The aim of this work is to evaluate the performance of the stirring 3D Fe/Al2O3 monolithic reactor in batch operation applied to the liquid-phase hydroxylation of phenol by hydrogen peroxide (H2O2). An experimental and numerical investigation was carried out at the following operating conditions: CPHENOL,0 = 0.33 M, CH2O2,0 = 0.33 M, T = 75–95 °C, P = 1 atm, ω = 200–500 rpm and WCAT ~ 1.1 g. The kinetic model described the consumption of the H2O2 by a zero-order power-law equation, while the phenol hydroxylation and catechol and hydroquinone production by Eley–Rideal model; the rate determining step was the reaction between the adsorbed H2O2, phenol in solution with two active sites involved. The 3D CFD model, coupling the conservation of mass, momentum and species together with the reaction kinetic equations, was experimentally validated. It demonstrated a laminar flow characterized by the presence of an annular zone located inside and surrounding the monoliths (u = 40–80 mm s−1) and a central vortex with very low velocities (u = 3.5–8 mm s−1). The simulation study showed the increasing phenol selectivity to dihydroxybenzenes by the reaction temperature, while the initial H2O2 concentration mainly affects the phenol conversion. [ABSTRACT FROM AUTHOR]

Compact and tubular TS-2 zeolite membrane is successfully fabricated on the mullite support by secondary hydrothermal synthesis. The mullite supports are fully covered by the aggregated walnut-shaped TS-2 zeolite crystals, which are the aggregates of fine and rod-shaped crystals and have high BET surface area, total pore capacity and mesoporous volume by advance isothermal characterization. The incorporation of the Ti atoms in framework positions of the MEL zeolite lattice and mainly form tetrahedrally coordinated titanium. Besides, influence of the crystallization temperature and time on the growth and catalytic performance are investigated in this work. The as-synthesized TS-2 zeolite membrane has a good catalytic performance for phenol hydroxylation by hydrogen peroxide. When the reaction temperature and molar ratio of phenol/hydrogen peroxide are 50 °C and 2, the flux, phenol conversion and dihydroxybenzene selectivity of TS-2 zeoite membrane are 6.43 kg m−2 h−1, 32.23% and 99.88%, respectively. [Display omitted] • Compact and tubular TS-2 zeolite membrane is successfully prepared. • Aggregated walnut-shaped TS-2 zeolites have high BET surface area, total pore capacity and mesoporous volume. • TS-2 zeolite membrane has a good catalytic performance for phenol hydroxylation by hydrogen peroxide. • Flux, phenol conversion and dihydroxybenzene selectivity of TS-2 zeoite membrane are 6.43 kg m−2 h−1, 32.23% and 99.88%. [ABSTRACT FROM AUTHOR]