Search

The development of acid-resistant and efficient corrosion inhibitors is of great significance for metal protection in many industrial processes. In this work, eight cases of sandwich-type polyoxometalate (POM)-based inorganic-organic hybrids, namely, carboxyethyltin and transition metal (TM) cofunctionalized tungstoantimonates and tungstobismuthates, formulated as Na

The catalytic performance of the selective isomerization of o-ethyltoluene (O-ET) is crucial to increasing the m-ethyltoluene (M-ET) and p-ethyltoluene (P-ET) yields. During the isomerization of O-ET, traditional (commercial) mordenites (HM) are generally limited by a high reaction temperature (235 °C), as well as a low yield of the isomerization product (49.0%). In this study, micro-mesoporous mordenites were obtained by treating commercial mordenites with NaOH, NaOH-HNO3, and NaOH-mixed acid (HNO3-oxalic). Thereafter, their structure, porosity, and acidity were investigated via X-ray diffraction, transmission electron microscopy, inductively coupled plasma, N2 sorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy of pyridine, temperature-programmed desorption of ammonia, and nuclear magnetic resonance. Among the various treated samples, the accessibility of the acidic sites and the B/L value of the alkali-mixed HNO3-oxalic one were enhanced, achieving the highest yield (53.6%) and lowest reaction temperature (165 °C), thus significantly reducing the energy consumption of the reaction process. Furthermore, Ni and Ce were successfully loaded via the incipient wetness impregnation of the micro-mesoporous mordenite to significantly prolong the catalytic life. This study affords a new strategy for obtaining high M-ET and P-ET yields from the isomerization of O-ET in mixed C9 aromatics on an industrial scale.

Environmental science & technology 56(23), 16546-16566 (2022). doi:10.1021/acs.est.2c02976, Published by American Chemical Society, Columbus, Ohio

We report here a new technique for the identification and visualization of functional domains in stratified metal–organic frameworks (MOFs). The technique, namely, gold diffusion enabled domain identification, utilizes the diffusion of Au nanoparticles within MOF cavities to track and selectively stain the more Au-philic domain in an MOF particle thereby allowing direct observation of domains, determination of domain sequences, and, in certain cases, domain boundaries under transmission electron microscopy. This method is an excellent tool for studying MOF materials with complex domain hierarchy., We report a new technique for the identification and visualization of functional domains in stratified metal−organic frameworks.

In the present paper, the reduction reaction of high-purity MoO3 with CO-15 vol % CO2 mixed gases in the temperature range of 901-948 K is investigated via the thermogravimetric analysis technology. The results show that reduction of MoO3 to MoO2 follows a three-step reaction process, viz., MoO3 is first reduced into Mo9O26, followed by Mo4O11, and finally to MoO2. The reaction sequences of MoO3 → Mo9O26 → Mo4O11 → MoO2 are proposed, which are quite different from those observed on reduction of MoO3 by pure H2 or CO gases. Pure Mo9O26 and Mo4O11 could be synthesized once suitable time was controlled. Rate-controlling steps for the reduction from MoO3 to Mo9O26 and Mo9O26 to MoO2 (include both Mo9O26 to Mo4O11 and Mo4O11 to MoO2) are interfacial chemical reactions, with the activation energies of 318.326 and 112.047 kJ/mol, respectively. This study also discovers that the as-synthesized MoO2 keeps the same platelet-shaped and smooth morphology as the MoO3 raw material; however, its particles size gradually increased as the reaction proceeds due to the formation of low-melting-point eutectic and the sticking of different particles.

[Image: see text] We report the structural analysis of highly drug-resistant human immunodeficiency virus protease (PR) variant PR(S17), rationally selected by machine learning, in complex with substrate analogues. Crystal structures were solved of inhibitor-free inactive PR(S17)-D25N, wild-type PR/CA-p2 complex, and PR(S17) in complex with substrate analogues, CA-p2 and p2-NC. Peptide analogues p2-NC and CA-p2 exhibit inhibition constants of 514 and 22 nM, respectively, for PR(S17) or approximately 3-fold better than for PR. CA-p2 is a better inhibitor of PR(S17) than are clinical inhibitors (K(i) = 50–8390 nM) except for amprenavir (K(i) = 11 nM). G48V resistance mutation induces curled flap tips in PR(S17)-D25N structure. The inner P2–P2′ residues of substrate analogues in PR(S17) complexes maintain similar conformations to those of wild-type complex, while significant conformational changes are observed in the peripheral residues P3, P4′ of CA-p2 and P3, P4, and P3′ of p2-NC. The loss of β-branched side chain by V82S mutation initiates a shift in 80’s loop and reshapes the S3/S3′ subsite, which enhances substrate binding with new hydrogen bonds and van der Waals interactions that are absent in the wild-type structures. The steric hindrance caused by G48V mutation in the flap of PR(S17) contributes to altered binding interactions of P3 Arg, P4′ norleucine of CA-p2, and P4 and P3′ of p2-NC with the addition of new hydrogen bonds and van der Waals contacts. The enhanced interaction of PR(S17) with substrate analogues agrees with their relative inhibition, suggesting that this mutant improves substrate binding while decreasing affinity for clinical inhibitors.

Four HIV-1 protease (PR) inhibitors, clinical inhibitors lopinavir and tipranavir, and two investigational compounds 4 and 5, were studied for their effect on the structure and activity of PR with drug-resistant mutation L76V (PRL76V). Compound 5 exhibited the best Ki value of 1.9 nM for PRL76V, whereas the other three inhibitors had Ki values of 4.5–7.6 nM, 2–3 orders of magnitude worse than for wild-type enzymes. Crystal structures showed only minor differences in interactions of inhibitors with PRL76V compared to wild-type complexes. The shorter side chain of Val76 in the mutant lost hydrophobic interactions with Lys45 and Ile47 in the flap, and with Asp30 and Thr74 in the protein core, consistent with decreased stability. Inhibitors forming additional polar interactions with the flaps or dimer interface of PRL76V were unable to compensate for the decrease in internal hydrophobic contacts. These structures provide insights for inhibitor design.

Large-scale membrane fabrication currently relies on the use of traditional solvents, such as N,N-dimethylacetamide, 1-methyl-2-pyrrolidinone, and dimethylformamide. These solvents are toxic, slowly biodegradable, and combustible, posing risks to human health and the environment, and requiring careful safety procedures. Replacing traditional solvents with green solvents while maintaining or improving the membrane performance is a challenging task at the forefront of research and development in the field of membrane technology. We employed a novel green solvent, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv PolarClean), to prepare high-performance poly(vinyl chloride) ultrafiltration membranes. This green solvent was used to completely replace toxic solvents during membrane fabrication, for the first time. The effects of polymer concentration, addition of amphiphilic copolymer poly(vinyl chloride)-graft-poly(ethylene glycol) methyl ether methacrylate concentration, and use of a nonwoven polyethylene terephthalate fabric as support layer were investigated systematically. The membrane fabricated with 8% PVC, 5% PVC-g-PEGMA, and nonwoven PET fabrics as support layer showed the best overall performance, presenting small and narrowly distributed membrane pores, high surface porosity, smooth surface, ultrahigh pure water permeability coefficients of >5000 L m h bar, high sodium alginate rejection of nearly 98%, and flux recovery ratio of 57%. This study demonstrates the feasibility of using green solvent to increase the sustainability and effectiveness of membrane processes.

A novel metal-free double SO2 insertion/multicomponent bicyclization cascade of benzene-linked 1,7-diynes has been established by treatment with aryldiazonium tetrafluoroborates and DABCO–bis(sulfu...

Aprotic lithium–air batteries have recently drawn considerable attention due to their ultrahigh specific energy. However, the chemical and electrochemical instability of the electrolyte is one of the most critical issues that need to be overcome. To increase the stability and maintain a relatively high conductivity of the lithium ion, a mixed electrolyte of sulfolane (TMS) and N,N-dimethylacetamide (DMA) was evaluated and tested in an aprotic lithium–air battery. The physical and chemical characterizations showed that the mixed electrolyte exhibited a relatively low viscosity, high ionic conductivity and oxygen solubility, and good stability. In addition, it was found that lithium–air batteries with an optimized electrolyte composition (DMA/TMS = 20:80, % v/v) showed a better cycle life and lower charge overpotential as compared to those with electrolytes with a single solvent, either DMA or TMS.