Layer-Contacted Graphene-Like BN/Ultrathin Bi_(3)O_(4)Br Stacking for Boosting Photocatalytic Molecular Oxygen Activation

Novel graphene-like boron nitride(BN)/Bi_(3)O_(4)Br photocatalysts have been controllably synthesized through a facile solvothermal method for the first time. Layer contact stacking between graphene-like BN and ultrathin Bi_(3)O_(4)Br was achieved with strong interaction. Dehalogenation is designed to harvest more visible light, and the ultrathin structure of Bi_(3)O_(4)Br is designed to accelerate charge transfer from inside to the surface. After graphene-like BN was engineered, photocatalytic performance greatly improved under visible light irradiation. Graphene-like BN can act as a surface electron-withdrawing center and adsorption center, facilitating molecular oxygen activation. O_(2)^(·-)was determined to be the main active species during the degradation process through analyses of electron spin resonance and XPS valence band spectra.

Selective oxidation of ethylbenzene catalyzed by fluorinated metalloporphyrins with molecular oxygen

This paper reported the oxidation of ethylbenzene catalyzed by fluorinated metalloporphyrins under mild conditions without any additives. The results showed that the cobalt(II)(5,10,15,20-tetrakis(pentafluorophenyl))porphyrin was the best catalyst among the fluorinated metalloporphyrins. The conversion of ethylbenzene reached 38.6%, the selectivity to acetophenone reached 94.0%, and the turnover number is 2719 under the optimal conditions.

Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen

Preparation of dispersed transition metal oxides catalyst with low oxidation state still remains a challenging task in heterogeneous catalysis.In this study,vanadium oxides supported on zeolite SBA-15 have been prepared under hydrothermal condition using V 2 O 5 and oxalic acid as sources of vanadium and reductant,respectively.The structures of samples,especially the oxidation state of vanadium,and the surface distribution of vanadium oxide species,have been thoroughly characterized using various techniques,including N 2-physisorption,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,UV-visible spectra（UV-Vis） and UV-visible-near infrared spectra（UV-Vis-NIR）.It is found that the majority of supported vanadium was in the form of vanadium（IV） oxide species with the low valence of vanadium.By adjusting hydrothermal treatment time,the surface distribution of vanadium（IV） oxide species can be tuned from vanadium（IV） oxide cluster to crystallites.These materials have been tested in the hydroxylation of benzene to phenol in liquid-phase with molecular oxygen in the absence of reductant.The catalyst exhibits high selectivity for phenol（61%） at benzene conversion of 4.6%,which is a relatively good result in comparison with other studies employing molecular oxygen as the oxidant.

Molecular oxygen activation enhancement by BiOBr0.5I0.5/BiOI utilizing the synergistic effect of solid solution and heterojunctions for photocatalytic NO removal

To improve the photocatalytic oxidation reaction activity for NO removal, photocatalysts with excellent activity are required to activate molecular oxygen. Solid solution and heterojunction were suggested as effective strategies to enhance the molecular oxygen activation viaexciton and carrier photocatalysis. In this study, a solid solution and heterojunction containing BiOBr0.5I0.5/BiOI catalyst was synthesized, and it showed improved photocatalytic activity for removing NO. The photocatalytic NO removal mechanism indicated that synergistic effects between the solid solution and heterojunction induced the enhanced activity for molecular oxygen activation. The photogenerated holes, superoxide, and singlet oxygen generated by the carrier and exciton photocatalysis supported the high photocatalytic NO removal efficiency. This study provides new ideas for designing efficient Bi-O-X(X = Cl, Br, I) photocatalysts for oxidation reactions.

Gas-phase epoxidation of propylene by molecular oxygen over Ag-Cu-Cl/BaCO_3 catalyst:Effects of Cu and Cl loadings

Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.

Iodine-doping-assisted tunable introduction of oxygen vacancies on bismuth tungstate photocatalysts for highly efficient molecular oxygen activation and pentachlorophenol mineralization

In this work,the tunable introduction of oxygen vacancies in bismuth tungstate was realized via asimple solvothermal method with the assistance of iodine doping.With the predictions afforded bytheoretical calculations,the as-prepared bismuth tungstate was characterized using various tech-niques,such as X-ray diffraction,Raman spectroscopy,scanning electron microscopy,transmissionelectron microscopy,X-ray photoelectron spectroscopy,electron spin resonance spectroscopy,anduV-Vis diffuse reflectance spectroscopy.The different concentrations of the oxygen vacancies onbismuth tungstate were found to be intensely correlated with iodine doping,which weakened thelattice oxygen bonds.Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as aresult of iodine doping,the molecular oxygen activation was remarkably enhanced,thus endowingbismuth tungstate with high activity for the photocatalytic degradation of sodium pentachloro-phenate.More encouraging is the total organic carbon removal rate of sodium pentachlorophenateover iodine-doped bismuth tungstate that exceeded 90%in only 2 h and was 10.6 times higher thanthat of the pristine bismuth tungstate under visible light irradiation.Moreover,the mechanism,through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tung-state is enhanced,was speculated based on the results of radical detection and capture experiments.This work provides a new perspective for the enhanced photocatalytic degradation of organochlo-rine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-dopedbismuth tungstate.

Oxidation of Styrene with Molecular Oxygen in Supercritical CO_2

The oxidation of styrene with molecular oxygen catalyzed by PdCl2+CuCl2 has been investigated in supercritical CO2 with a batch reactor. The oxidative system of styrene contains four components at the beginning and seven components during the reaction. The critical temperature, critical pressure, and critical density at different conversions are determined by using a high-pressure view cell. The effect of phase behavior on the conversion and selectivity were studied. Experimental results showed that the critical parameters of the reaction mixture at fixed initial molar ratio changed with the conversion of reactant. The conversion of styrene reached maximum near the critical density of the reaction mixture. Product selectivity also varied with density of reaction mixture and could be tuned to some degree.

Catalytic Oxidative Conversion from Naphthol to 2-Hydroxy-1, 4-naphthoquinone over Iron Porphyrin Catalysts by Molecular Oxygen in an Alkaline 2-Propanol Solution

In an alkaline 2-propanol solution with 5,10,15,20-tetra(4-methoxyl phenyl) porphyrin iron chloride(TOMPPFeCl) as a catalyst and oxygen as a cheap green oxidant, 2-naphthol was conversed to 2-hydroxy-\{1,4-naphthoquinone(HNQ)\} with a yield of 62.17% and a selectivity of 100%, and the conversion number of TMOPPFeCl catalyst was 8.32/min. The catalytic oxidation products were characterized by means of UV-Vis, IR, GC-MS, ~ 1H NMR and melting point determination. In this catalytic oxidation, the catalytic activity of TMOPPFeCl was researched in detail and the reacting conditions were optimized. A possible reaction mechanism is summarized based on in situ EPR determination.

Chemoselective epoxidation of electron-deficient olefins with molecular oxygen via conjugated olefins epoxidation and BHT hydroxylation

The chemoselective epoxidation of electron-deficient olefins in the presence of electron-rich alkene moieties is reported.This chemoselective epoxidation strategy undergoes a conjugated olefin epoxidation and BHT hydroxylation process to give various useful oxiranes in high yields,especially for the 2-substituted 2-trifluoromethyloxiranes.Importantly,this protocol features mild conditions,is transition-metal free,operationally simple,and gram-scalable,and tolerates diverse functional groups.Drug candidate HSD-16 is synthesized smoothly by this protocol.Mechanism studies indicate molecular oxygen is the terminal oxidant and the O-source of the oxiranes.

Propylene epoxidation coupled with furfural oxidation over Pt(Ⅱ) TPP porphyrin with molecular oxygen

The development of green route for preparing propylene oxide(PO)with molecular oxygen is of significance both in academic and industrial.In this work,propylene epoxidation coupled with furfural oxidation catalyzed by platinum meso-tetraphenylporphyrin(Pt(Ⅱ)TPP)has been developed.Propylene conversion and PO selectivity reached up to 56%and 83%,respectively.Meanwhile,furfural was almost completely converted to furoic acid.Based on operando characterizations and electron paramagnetic resonance(EPR)tests,a mechanism involved high-valent Pt species was proposed.This work is expected to provide a potential application prospects for producing PO and furoic acid simultaneously in chemical industry.

Highly Efficient Oxidative Cleavage of Carbon-Carbon Double Bond over meso-Tetraphenyl Cobalt Porphyrin Catalyst in the Presence of Molecular Oxygen

Highly efficient and selective carbon-carbon double bond aerobic cleavage of olefins catalyzed by metallopor- phyrins was investigated, and carbonyl compounds and epoxide were produced as the main products. CoTPP （co- balt meso-tetraphenyl porphyrin） showed excellent activity for the oxidative cleavage of carbon-carbon double bond by using styrene as model compound, in which the TOF （turnover frequency） and selectivity toward benzaldehyde was obtained with 2×10^4h-1 and 86%,respectively.

Crown ether-appended Fe(Ⅲ) porphyrin:Synthesis,characterization and catalytic oxidation of cyclohexene with molecular oxygen

A new crown ether appended Fe（Ⅲ） porphyrin complex was prepared by sulfuryl chloride appended benzo-15-crown-5 to the meso position of meso-5,10,15,20-tetra（4-hydrophenyl）porphyrin,and it was applied to catalytic oxidation of cyclohexene with molecular oxygen without reductant,showing a remarkable catalytic activity（conversion is up to 94%） and selectivity for 2-cyclohexen-1-ol（73%）.

InP quantum dots on g-C_(3)N_(4) nanosheets to promote molecular oxygen activation under visible light

Largely limited by the high dissociation energy of the O—O bond,the photocatalytic molecular oxygen activation is highly challenged,which re strains the application of photocatalytic oxidation technology for atmospheric pollutants removal.Herein,we design and fabricate the InP QDs/g-C_(3)N_(4) compounds.The introduction of InP QDs promotes the charge transfer within the interface resulting in the effective separation of photo-generated carriers.Furthermore,InP QDs greatly facilitates the activation of molecular oxygen and promote the formation of O_(2)·under visible-light illuminatio n.These conclusions are identified by experimental and calculation results.Hence,NO can be combined with the O_(2)·to form O—O—N—O intermediate to direct conversion into NO_(3).As a result,the NO removal ratio of g-C_(3)N_(4) has a one fold increase after InP QDs loaded and the generation of NO_(2) is effectively inhibited.This wo rk may provide a strategy to design highly efficient materials for molecular oxygen activation.

Iron sites on defective BiOBr nanosheets:Tailoring the molecular oxygen activation for enhanced photocatalytic organic synthesis

Sunlight-driven activation of molecular oxygen(O_(2))for organic oxidation reactions offers an appealing strategy to cut down the reliance on fossil fuels in chemical industry,yet it remains a great challenge to simultaneously tailor the charge kinetics and promote reactant chemisorption on semiconductor catalysts for enhanced photocatalytic performance.Herein,we report iron sites immobilized on defective BiOBr nanosheets as an efficient and selective photocatalyst for activation of O_(2) to singlet oxygen(^(1)O_(2)).These Fe^(3+) species anchored by oxygen vacancies can not only facilitate the separation and migration of photogenerated charge carrier,but also serve as active sites for effective adsorption of 02.Moreover,low-temperature phosphorescence spectra combined with X-ray photoelectron spectroscopy(XPS)and electronic paramagnetic resonance(EPR)spectra under illumination reveal that the Fe species can boost the quantum yield of excited triplet state and accelerate the energy transfer from excited triplet state to adsorbed O2 via a chemical loop of Fe^(3+)/Fe^(2+),thereby achieving highly efficient and selective generation of ^(1)O_(2).As a result,the versatile iron sites on defective BiOBr nanosheets contributes to near-unity conversion rate and selectivity in both aerobic oxidative coupling of amines to imines and sulfoxidation of organic sulfides.This work highlights the significant role of metal sites anchored on semiconductors in regulating the charge/energy transfer during the heterogeneous photocatalytic process,and provides a new angle for designing high-performance photocatalysts.

Designed polymeric conjugation motivates tunable activation of molecular oxygen in heterogeneous organic photosynthesis

Photocatalytic oxidative organic reactions are important synthetic transformations,and research on reaction selectivity by reactive oxygen species(ROS)is significant.To date,however,there has rarely been any focus on the directed generation of ROSs.Herein,we report the first identification of tunable molecular oxygen activation induced by polymeric conjugation in nonmetallic conjugated microporous polymers(CMP).The conjugation between these can be achieved by the introduction of alkynyl groups.CMP-A with an alkynyl bridge facilitates the intramolecular charge mobility while CMP-D,lacking an alkynyl group enhances the photoexcited carrier build-up on the surface from diffusion.These different processes dominate the directed ROS generation of the superoxide radical(·O_(2)^(-))and singlet oxygen(^(1)O_(2)),respectively.This theory is substantiated by the different performances of these CMPs in the aerobic oxidation of sulfides and the dehydrogenative coupling of amines,and could provide insight into the rational design of CMPs for various heterogeneous organic photosynthesis.

Catalytic Oxidation of Cyclohexene with Molecular Oxygen on Hydrotalcite－like Compounds

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Synthesis of Cyanobenzaldehydes (m-, o-, p-) by Molecular Oxygen Oxidation Methods

Cyanobenzaldehydes (m-, o-, p-) were synthesized by oxidation ofcorresponding tolunitriles with molecular oxygen, catalyzed by cobalt acetate and sodium bromide.

Molecular oxygen-mediated selective hydroxyalkylation and alkylation of quinoxalin-2(1H)-ones with alkylboronic acids

Herein, an efficient molecular oxygen-mediated method for the selective hydroxyalkylation and alkylation of quinoxalin-2(1 H)-ones with alkylboronic acids under transition-metal free conditions has been developed. This strategy demonstrates a broad scope of quinoxalin-2(1 H)-ones and alkylboronic acids, giving3-hydroxyalkylquinoxalin-2(1 H)-ones and 3-alkylquinoxalin-2(1 H)-ones in moderate-to-good yield. Control experiments reveal that a radical pathway is involved.

Photooxidation of Hantzsch 1,4-dihydropyridines by molecular oxygen

Photooxidation of Hantzsch 1,4-dihydropyridines (1,4-DHP,1a-1d) by direct irradiation (λ > 300 nm) under an oxygen atmosphere has been carefully examined in this work. Spectroscopic and electrochemical studies demonstrate that photoinduced singlet electron transfer from 1,4-DHP to molecular oxygen occurs. The generated superoxide radical anion (O2-·) is responsible for this typical photochemical oxidation.

草酸与铁氧化物相互作用及光化学活化分子氧过程的研究进展

草酸与铁氧化物共存于自然环境中,二者之间的相互作用及光化学行为强烈影响着分子氧的活化.而分子氧活化影响共存体系中污染物的迁移与转化,是发展绿色污染控制氧化技术的关键.因此,探讨草酸与铁氧化物之间的相互作用与光化学活化分子氧是目前的研究热点之一.本文系统总结了近年来围绕草酸与铁氧化物相互作用以及草酸诱导铁氧化物活化分子氧的研究成果,论述了草酸在铁氧化表面的吸附与转化特性、草酸铁络合物光化学过程以及活性氧产生与转移途径,同时探讨了上述过程对环境污染物降解的影响,借此加深理解草酸诱导铁氧化物环境光化学行为与活化分子氧原理,并对今后的研究发展方向提出了展望,以期为利用天然铁氧化物和有机质发展原位环境修复技术提供依据.