Cobalt-manganese bimetallic organic frameworks catalyzed solvent-free oxidation of benzyl C-H bonds with O_(2) as sole oxidant

The selective oxidation of hydrocarbons can be used to produce oxygen-containing functional compounds such as alcohols, aldehydes or ketones and its efficient and green conversion lies in the development of efficient catalysts that activate C-H bonds and O_(2) simultaneously. In this work, the bimetallic organic framework (CoMnBDC) material with morphology of stacked nanosheets was synthesized using terephthalic acid as ligands to coordinate with Co^(2+) and Mn^(2+) cations under solvothermal conditions. As revealed by spectroscopic characterizations, the electron transfer from Mn to Co in the CoMnBDC resulted in the reduction of the Co average oxidation state and increase of the Mn average oxidation state. The CoMnBDC nanosheets were used as catalyst in catalytic oxidation of ethylbenzene, in which the redox effect promotes the effective electron transfer, the activation of O_(2) and benzyl C-H bond. The 96.2% conversion of ethylbenzene and 98.0% selectivity towards acetophenone could be obtained with oxygen as sole oxidant and solvent-free condition. The excellent catalytic performance is related to the structure of CoMnBDC and is also the best when compared with reported results. Various types of aromatic hydrocarbons containing benzyl C-H bonds can be effectively oxidized by CoMnBDC to produce corresponding ketone products. The density functional theory (DFT) calculation revealed that the redox effect leads to the relative enrichment of electrons on Co in CoMnBDC, which is conducive to the activation of O_(2);Mn with higher oxidation state is beneficial for the adsorption of ethylbenzene and activation of C-H bonds. The CoMnBDC has a lower energy barrier for transition state, making it easier for the ethylbenzene oxidation to produce acetophenone.

Simulation Monitoring for Rainfall Infiltration in Soil Based on High Density Electrical Method

Rainfall infiltration is a porous medium flow problem with variable saturation. Based on the theoretical analysis of the flow field, electrical conductivity of rocks, the electrical field, the paper simulates the coupling relationship between the water saturation in soil and the apparent resistivity distribution. It combines the Richards equation, the Archie formula and the Laplace equation. The experiment simulates the potential field data by the Wenner setting in electrical exploration on a two-layer geologic model with continuous rainfall during 5 days, which shows that the effective saturation in soil is increasing with the rainfall time, while the apparent resistivity is decreasing. This can provide a theoretical basis for the analyzing the rainfall infiltration and porosity of the soil by using high-density electrical method in the future.

Effect of Microwave Irradiation on Dipeptides and Proteins Derived from Silk During Solvation

Silkworm silk and spider silk have been attracting numerous interests.Rapid solvation of silkworm silk protein and spider silk protein without hydrolysis of peptide bonds is highly desirable.Microwave irradiation has been proposed for facile extraction of water-soluble silk protein by various liquid media.However,microwave exposure can cause hydrolysis of peptide bonds,leading to irreversible degradation of silk protein.In this study,a series of representative dipeptides and a rationally designed recombinant protein derived from silk protein is employed to investigate the efect of microwave on the stability of the peptide bonds during a long time dissolution process,i.e.,heating at 60℃in a CaCl_(2):CH_(3)CH_(2)OH:H_(2)O(1:2:8)solution.Results demonstrate that microwave irradiation imposes a minor damage and a negligible cleavage of the peptide bonds,compared with the conventional heating method.The microwave irradiation treatment suggested in this is suitable for dissolution of silk protein.It is anticipated that this approach can be developed to a commercial level commercially.

Research on FBG-Based CFRP Structural Damage Identification Using BP Neural Network

A damage identification system of carbon fiber reinforced plastics （CFRP） structures is investigated using fiber Bragg grating （FBG） sensors and back propagation （BP） neural network. FBG sensors are applied to construct the sensing network to detect the structural dynamic response signals generated by active actuation. The damage identification model is built based on the BP neural network. The dynamic signal characteristics extracted by the Fourier transform are the inputs, and the damage states are the outputs of the model. Besides, damages are simulated by placing lumped masses with different weights instead of inducing real damages, which is confirmed to be feasible by finite element analysis （FEA）. At last, the damage identification system is verified on a CFRP plate with 300mm × 300mm experimental area, with the accurate identification of varied damage states. The system provides a practical way for CFRP structural damage identification.

Engineering electrophilic atomic Ir sites on CeO_(2) colloidal spheres for selectivity control in hydrogenation of α,β-unsaturated carbonyl compounds

Selective hydrogenation of the carbonyl bond inα,β-unsaturated carbonyl compounds is rather challenging owing to the more feasible hydrogenation of ethylenic bond from both thermodynamic and kinetic aspects.Here,we demonstrate a facile emulsionbased molecule-nanoparticle self-assembly strategy for the atomic engineering of Ir species on three-dimensional CeO_(2)spheres(Ir1@CeO_(2)).When applied to the hydrogenation ofα,β-unsaturated aldehydes,Ir1@CeO_(2)catalyst remarkably exhibited~100%selectivity towards unsaturated alcohols,whereas the formation of Ir nanoparticles on CeO_(2)drastically decreased the selectivity for unsaturated alcohols.Spectroscopic studies revealed that strong metal-support interactions triggered the charge transfer from Ir to CeO_(2),leading to the partial reduction of Ce^(4+)to Ce^(3+)along with the formation new Ir^(δ+)-O_(2)--Ce^(3+)(OV)interfaces.The electrophilic atomic Ir species at the Ir^(δ+)-O_(2)--Ce^(3+)(OV)interfaces would therefore preferentially adsorb and facilitate hydrogenation of polar C=O bond to achieve exceptional selectivity.

Insight into sulfur and iron effect of binary nickel-iron sulfide on oxygen evolution reaction

Nickel-iron sulfide has shown attractive activity in electrocatalytic oxygen evolution reaction(OER).However,the effects of low valence sulfur(S^(2−))and metal species on OER in binary nickel-iron sulfide have rarely been systematically studied.Works based on post-catalysis characterization have led to the assumption that the real active species are nickel-iron oxyhydroxide,and that nickel-iron sulfide acts only as a precatalyst.Therefore,to study the role of S,Ni,and Fe for the development of nickel-iron sulfide catalyst is of self-evident importance.Herein,a facile solvothermal method is used to synthesize acetylene black coated with nickel-iron sulfide nanosheets.Electrochemical tests show that the presence of low valence S species makes the catalyst have faster OER kinetics,larger active area,and intermediate active species adsorption area.Therefore,the present study reveals the enhancing effect of low valence sulfur species(S^(2−))on OER in binary nickel-iron sulfide.In situ Raman spectroscopy shows that the generation ofγ-NiOOH intermediate is essential and Fe does not directly participate in the oxygen production.Density functional theory(DFT)calculation shows that Ni-OH deprotonation is a rate-determining step for both binary nickel-iron sulfide and nickel sulfide.The addition of Fe into NiSx lightly increases the charge transfer of Ni atom to O atom,which makes deprotonation easier and thereby improves the OER performance.