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The widely used β-lactam antibiotics such as penicillins and cephalosporins are known to be susceptible to Cu11-catalyzed hydrolysis at their four-membered β-lactam ring. However, this study elucidates that Cu11 can in fact play multiple roles in promoting the hydrolysis and/or oxidation of β-lactam antibiotics under environmental aquatic conditions (pH 5.0-9.0 and 22 °C), depending on β-lactams' structural characteristics and solution pH. Most significantly, the β-lactam antibiotics that contain a phenylglycine primary amine group on the side chain can undergo direct oxidation by Cu11 via this functional group. On the other hand, the β-lactam ring of penicillins is susceptible to Cu11- catalyzed hydrolysis, followed by oxidation of the hydrolysis product by Cu11. In contrast, the β-lactam ring of cephalosporins is susceptible to Cu11-catalyzed hydrolysis only. Solution pH influences the Cu11-promoted transformation by affecting the β-lactam and Cu11 complexation through protonation/deprotonation of critical organic functional groups. When Cu11 acts as an oxidant to promote the transformation of β-lactam antibiotics to yield Cu1, the overall role of Cu appears catalytic if the reaction occurs under ambient atmospheric condition, due to quick oxidation of Cu1 by oxygen to regenerate CuH. Compared to earlier literature that largely assumed only the hydrolytic catalyst role of Cu11in promoting degradation of β -lactam antibiotics, the oxidative roles of Cu11 identified by this study mark important contributions to a more accurate mechanistic understanding. [ABSTRACT FROM AUTHOR]

Herein, we report a AgF-mediated regio- and stereoselective acetoxyselenylation of terminal/internal alkynes from iodobenzene dicarboxylate [PhI(OCOR) 2 ] and diorganyl diselenides via multiple-site functionalization to afford β-selenyl enol esters in good yields. Alkynes derived from bioactive molecules, such as l(-)-borneol, l-menthol, and acyne oxalate, are also suitable for this transformation and afford the expected compounds.

Peracetic acid (PAA) is an emerging oxidant and disinfectant for wastewater (WW) treatment due to limited harmful disinfection byproduct (DBP) formation. Nitrite (NO 2 - ) is a ubiquitous anion in water, but the impact of NO 2 - on PAA oxidation and disinfection has been largely overlooked. This work found for the first time that NO 2 - could significantly promote the oxidation of sulfonamide antibiotics (SAs) by PAA. Unexpectedly, the reactive nitrogen species (RNS), for example, peroxynitrite (ONOO - ), rather than conventional organic radicals (R-O • ) or reactive oxygen species (ROS), played major roles in SAs degradation. A kinetic model based on first-principles was developed to elucidate the reaction mechanism and simulate reaction kinetics of the PAA/NO 2 - process. Structural activity assessment and quantum chemical calculations showed that RNS tended to react with an aromatic amine group, resulting in more conversion of NO 2 - -N to organic-N. The formation of nitrated and nitrosated byproducts and the enhancement of trichloronitromethane formation potential might be a prevalent problem in the PAA/NO 2 - process. This study provides new insights into the reaction of PAA with NO 2 - and sheds light on the potential risks of PAA in WW treatment in the presence of NO 2 - .

In the face of increasingly severe electromagnetic (EM) wave pollution, the research of EM wave absorbing materials is an effective solution. To reduce the density of traditional absorbing materials, in this work, FeCo/CoFe 2 O 4 /carbon nanofiber composites were successfully prepared by electrospinning for the EM wave attenuation application. Benefiting from the loss ability of interface polarization, dipole polarization, and magnetic loss, the composites obtained a bandwidth of 5.0 GHz at a 1.95 mm thickness and an absorption peak of -52.3 dB. More importantly, the radar cross section (RCS) reduction of composite coatings calculated by ANSYS Electronics Desktop 2018 (HFSS) can reach 34.5 dBm 2 , and the RCS value is almost less than -10 dBm 2 when the incident angle is greater than 20°, demonstrating great scattering ability of the material coating to EM waves. This work, combined with the exploration of the mechanism and the simulation analysis of the absorbing coating, will be of significance for the development of absorbing materials.

Taking serious microwave pollution issues and the complex application environment into consideration, it is quite urgent to integrate several functions into one material. Electromagnetic (EM) absorbing materials with multiple functions are highly attractive to next-generation wireless techniques and portable electronic devices. Herein, melamine foam provides a decent platform for the uniform growth of Co-based metal-organic frameworks (MOFs), which bring the as-obtained hybrid foam with three-dimensional porous network structure and combination of dielectric along with magnetic attenuation abilities as advanced materials in multifunctional fields. Remarkably, the relevant microwave absorption (MA) performance of the hybrid foam can reach an extremely high reflection loss value of -59.82 dB. Furthermore, the hybrid foam exhibits excellent infrared stealth and optimiztic heat insulation function, demonstrating the potential in plenty of practical applications. These results may arouse interests and inspirations of the elaborately design and facilely synthesis of high-performance foamlike microwave absorbers with multiple functions.

Developing green 3D porous materials integrating multitasking environmental remediation with high efficiency and reusability is considered to be a promising sustainable approach and is urgently required. Herein, we have successfully prepared a facile, ecofriendly, and robust multifunctional composite sponge of carbon nitride (CN) nanosheets wrapping an elastomer polydimethylsiloxane (PDMS) skeleton without harsh treatments. The composite sponge (CN@PDMS) exhibits excellent hydrophobic and superoleophilic properties with a water contact angle of 133.2°. This sponge also shows high selective absorption of organic solvents and oils with high recyclability after 10 absorption cycles. Furthermore, the CN@PDMS sponge has a high ability for demulsification of the oil-in-water emulsion as well. The as-prepared sponge displays high thermal stability, retaining 82.16% of its original weight up to 550 °C, and extraordinary prolonged stability in harsh corrosive solutions over 35 h compared with the pristine PDMS sponge. Additionally, the CN@PDMS sponge exhibits a high ability for adsorption and photodegradation of rhodamine B under visible light irradiation with self-cleaning and high reusability over 5 runs. Such a sustainable strategy would provide new ways for broad environmental applications., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

While the β-lactam antibiotics are known to be susceptible to oxidative degradation by sulfate radical (SO 4 •- ), here we report that peroxymonosulfate (PMS) exhibits specific high reactivity toward β-lactam antibiotics without SO 4 •- generation for the first time. Apparent second-order reaction constants (k 2,app ) were determined for the reaction of PMS with three penicillins, five cephalosporins, two carbapenems, and several structurally related chemicals. The pH-dependency of k 2,app could be well modeled based on species-specific reactions. On the basis of reaction kinetics, stoichiometry, and structure-activity assessment, the thioether sulfur, on the six- or five-membered rings (penicillins and cephalosporins) and the side chain (carbapenems), was the main reaction site for PMS oxidation. Cephalosporins were more reactive toward PMS than penicillins and carbapenems, and the presence of a phenylglycine side chain significantly enhanced cephalosporins' reactivity toward PMS. Product analysis indicated oxidation of β-lactam antibiotics to two stereoisomeric sulfoxides. A radical scavenging study and electron paramagnetic resonance (EPR) technique confirmed lack of involvement of radical species (e.g., SO 4 •- ). Thus, the PMS-induced oxidation of β-lactam antibiotics was proposed to proceed through a nonradical mechanism involving direct two-electron transfer along with the heterolytic cleavage of the PMS peroxide bond. The new findings of this study are important for elimination of β-lactam antibiotic contamination, because PMS exhibits specific high reactivity and suffers less interference from the water matrix than the radical process.

Penicillins, a class of widely used β-lactam antibiotics, are known to be susceptible to catalyzed hydrolysis by metal ions such as Cu(II). However, new results in this study strongly indicate that the role of Cu(II) is not merely a hydrolysis catalyst but also an oxidant. When benzylpenicillin (i.e., penicillin G (PG)) was exposed to Cu(II) ion at an equal molar ratio and pH 7, degradation of PG occurred rapidly in the oxygen-rich solution but gradually slowed down to a halt in the oxygen-limited solution. In-depth studies revealed that Cu(II) catalyzed hydrolysis of PG to benzylpenicilloic acid (PA) and oxidized PA to yield phenylacetamide and other products. The availability of oxygen played the role in reoxidizing Cu(I) back to Cu(II), which sustained fast degradation of PG over time. The overall reaction was also influenced by pH, with Cu(II)-catalyzed hydrolysis of PG occurring throughout pH 5, 7 and 9, while Cu(II) oxidation of PA occurring at pH 7 and 9. Note that the potential of Cu(II) to oxidize penicillins was largely overlooked in the previous literature, and catalyzed hydrolysis was frequently assumed as the only reaction. This study is among the first to identify the dual roles of Cu(II) in the entire degradation process of PG and systematically investigate the overlooked oxidation reaction to elucidate the mechanism. The new mechanistic knowledge has important implications for many other β-lactam antibiotics for their interactions with Cu(II), and significantly improves the ability to predict the environmental fate and transformation products of PG and related penicillins in systems where Cu(II) species are also present.