Iron oxychloride as an efficient catalyst for selective hydroxylation of benzene to phenol

Selective hydroxylation of benzene is a felicitous strategy for the production of phenol that is deemed to be an alternative to conventional processes. Thus, the development of a durable and highly efficient catalyst for the selective hydroxylation of benzene should be a key topic. In this work, FeOCl was prepared by a chemical vapor transition method and characterized using various techniques including XRD, TEM, Raman spectroscopy, N2 adsorption–desorption, DLS, and TGA. The prepared FeOCl was applied as a heterogeneous catalyst in benzene hydroxylation, and the reaction conditions were optimized. The acquired data manifested that FeOCl has shown superiority over the other reported catalysts utilized in benzene hydroxylation. The superiority of FeOCl is attributed to the facile self-redox potential of FeOCl and its remarkable ability for the production of an overwhelming amount of hydroxyl radicals in a short period of time. The catalyst recovery and reuse test showed that FeOCl is able to endure the harsh conditions of benzene hydroxylation for four runs. The mechanism of benzene hydroxylation using FeOCl as a catalyst in the presence of hydrogen peroxide as an oxidant was also illustrated

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Characterization and some physical studies of PVA/PVP filled with MWCNTs

Pristine films of polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) polymer blend filled with gradient contents of (MWCNTs) multi-walled carbon nanotubes have been prepared using ordinary casting technique. Fourier transform infrared (FT-IR) revealed the existence of main characteristic peaks corresponding to vibrational groups that characterized the synthesized samples. The interaction between nano-composite components was indicated by variation of main vibrational bands in the spectral range 1500–1750 cm−1. X-ray diffraction (XRD) confirms the structural modification in PVA/PVP matrix due to MWCNTs filling. Transmission electron microscopy (TEM (shows the presence of MWCNTs with a diameter between 80 and 30 nm and length of about several micrometers. Scanning electron microscopy (SEM) used to approve the homogenous nature of prepared samples. The absorption coefficient spectra show the appearance of two absorption peaks at 290 and 620 nm attributed to n → π* and π → π* electronic transitions. The optical energy gap (Eg) have been obtained from the indirect allowed transition. It was found that, Eg decrease with increasing MWCNTs content. Analysis of refractive index n showed a normal dispersion in the wavelength range 866–2500 nm, as well as an anomalous dispersion in the wavelength range 190–866 nm. The oscillator parameters (oscillator energy and dispersion energy) were calculated. The decrease in optical energy gap and the increase in refractive index due to filling with MWCNTs suppose the possibility of their use in optical devices. Keywords: MWCNTs, PVA, PVP, Refractive index, FTIR, UV/vi

Plasmon-Enhanced Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde Using BiVO4/BiOBr/Au Nanosheets

Plasmonic Au nanoparticles were deposited over photocatalytic BiVO4/BiOBr nanosheets with different loadings in the range of 0.5-5% (w/w) to boost the photocatalytic reactivity via surface plasmonic resonance. The results showed that the highest benzyl alcohol conversion (100%) and the maximum benzaldehyde yield (99%) were obtained using BiVO4/BiOBr/Au 3% after 4 h of irradiation. Electron paramagnetic resonance analysis and trapping experiments revealed that singlet oxygen is the dominant species produced within the system and suggest that it is the main species driving photocatalytic oxidation of benzyl alcohol to benzaldehyde. The proposed mechanism involves irradiation of BiVO4/BiOBr/Au with light to excite its electrons to the singlet state and produce singlet excitons, which eventually produces triplet excitons via intersystem crossing. Dissolved O2 subsequently reacts with these triplet excitons to produce singlet oxygen. Moreover, the energy barrier and the intrinsic reaction indicated that the reaction is thermodynamically favorable. These results demonstrate the unique effects of plasmonic resonance on photocatalytic activity, which can be adapted to different selective oxidation reactions

Cu2O Cubes Decorated with Azine-Based Covalent Organic Framework Spheres and Pd Nanoparticles as Tandem Photocatalyst for Light-Driven Degradation of Chlorinated Biphenyls

Covalent organic frameworks (COFs) are promising candidates for heterogeneous photocatalytic reactions, though highly efficacious semiconductor–metal assemblies are often required to foster their photocatalytic performance. Herein, we report an efficient photocatalytic hybrid material that involves loading azine-based COF spheres onto Cu2O cubes and decorating them with palladium nanoparticles. The photocatalytic performance of the material was studied via the light-driven degradation of chlorinated biphenyls. The Cu2O-ACOF-1@Pd system demonstrated an outstanding performance over the bare Cu2O or ACOF-1, which can be attributed to the synergistic effect induced by the multicomponent tandem photocatalyst. It is shown that for monochlorinated biphenyls, the congener with a chlorine atom in the para position is more vulnerable to degradation than its meta and ortho counterparts because of electronic effects and being less sterically hindered. Moreover, the presence of a chlorine atom in the para position as an electron donor increases the conjugation between the phenyl rings, which in turn increases the driving force for planarity that facilitates the removal of the chlorine atom. This trend could be attributed to the reactivity of superoxide radicals toward the different congeners of monochlorinated biphenyls. The data revealed that nucleophilic substitution occurring at the para position is characterized by the lowest Gibbs free energy, while that occurring at the ortho position is characterized by the highest Gibbs free energy

Hierarchical Core–Shell ACOF-1@BiOBr as an Efficient Photocatalyst for the Degradation of Emerging Organic Contaminants

We report the preparation of nanostructured ACOF-1@BiOBr with a hierarchical core–shell architecture and demonstrate its performance in the light-driven degradation of organic contaminants. The hierarchical core–shell photocatalyst was prepared using a facile solvothermal method that involves the formation of a BiOBr shell that encapsulates an azine-based covalent organic framework (ACOF-1) sphere. The ACOF-1@BiOBr hierarchical core–shell system manifested enhanced performance over the bare ACOF-1 or BiOBr in the photocatalytic degradation of different organic dyes employed in this study. Such an enhancement can be ascribed to the synergy between ACOF-1 and BiOBr, where the band gap alignment between ACOF-1 and BiOBr forms a Type-II heterostructure. In such a heterostructure, the movement of the photogenerated charge carriers can lower the recombination rate of the produced e–/h+ pairs and, hence, enhance the photocatalytic performance. The rate constants for photocatalytic degradation of the tested dyes were correlated to the surface interaction between the photocatalyst and the dyes. The data revealed that the generation of superoxide radicals was enhanced by the ACOF-1@BiOBr system, which demonstrates the significance of the multicomponent tandem photocatalyst. The hierarchical core–shell ACOF-1@BiOBr presents a paradigm shift in the development of covalent organic frameworks, especially in the field of photocatalysis

Cu₂S@Bi₂S₃Double-Shelled Hollow Cages as a Nanocatalyst with Substantial Activity in Peroxymonosulfate Activation for Atrazine Degradation

Metal dichalcogenides are promising candidates for heterogeneous catalysis. Designing them as a double-shelled hollow nanostructure can enhance their performance owing to the high surface area provided by the hollow inner space. Herein, we demonstrate a multistage templating approach to prepare double-shelled cages with Bi2S3 nanoparticles as an outer shell and Cu2S as an inner shell. A facile deposition method, coupled with a benign sulfidation process, has been developed to prepare such a double-shelled hollow structure. The prepared Cu2S@Bi2S3 double-shelled cages demonstrated a substantial catalytic reactivity in peroxymonosulfate (PMS) activation for the degradation of atrazine in the dark. Such performance is attributed to the synergy between Cu2S and Bi2S3 in activating PMS, which promotes radical generation and enhances the catalytic performance. Our mechanistic studies revealed that hydroxyl radicals and singlet oxygen are the dominant species generated during atrazine degradation

Glycolysis of Poly(ethylene terephthalate) Catalyzed by the Lewis Base Ionic Liquid [Bmim][OAc]

The glycolysis of poly­(ethylene terephthalate) (PET) was studied using 1-butyl-3-methylimidazolium acetate ([Bmim]­[OAc]) as a catalyst. The effects of temperature, time, ethylene glycol dosage, PET amount, and [Bmim]­[OAc] dosage on the glycolysis reaction were examined. The results revealed that [Bmim]­[OAc] has a PET conversion of 100% and a bis­(2-hydroxyethyl)­terephthalate (BHET) yield of 58.2% under the optimum conditions of 1.0 g of [Bmim]­[OAc] with 20 g of ethylene glycol in the presence of 3.0 g of PET at 190 °C after 3 h of glycolysis. The ionic liquid could be reused up to six times with no apparent decrease in the conversion of PET or yield of BHET. The pH plays a major role in explaining the proposed mechanism of glycolysis using the Lewis base ionic liquid [Bmim]­[OAc]. The kinetics of the reaction was first-order with an activation energy of 58.53 kJ/mol