Axially chiral arylpyrroles are key components of pharmaceuticals and natural products as well as chiral catalysts and ligands for asymmetric transformations. However, the catalytic enantioselective ...construction of optically active arylpyrroles remains a formidable challenge. Here we disclose a highly efficient strategy to access enantioenriched axially chiral arylpyrroles by means of organocatalytic atroposelective desymmetrization and kinetic resolution. Depending on the remote control of chiral catalyst, the arylpyrroles were obtained in high yields and excellent enantioselectivities under mild reaction conditions. This strategy tolerates a wide range of functional groups, providing a facile avenue to approach axially chiral arylpyrroles from simple and readily available starting materials. Selected arylpyrrole products proved to be efficient chiral ligands in asymmetric catalysis and also important precursors for further synthetic transformations into highly functionalized pyrroles with potential bioactivity, especially the axially chiral fully substituted arylpyrroles.
This article deals with the issue of asymptotic stabilization for a linear parabolic partial differential equation (PDE) with an unknown space‐varying reaction coefficient and multiple local ...piecewise uniform control. Clearly, the unknown reaction coefficient belongs to a function space. Hence, the fundamental difficulty for such issue lies in the lack of a conceptually simple but effective parameter identification technique in a function space. By the Lyapunov technique combined with a variant of Poincaré‐Wirtinger inequality, an update law is derived for estimate of the unknown reaction coefficient in a function space. Then a spatiotemporal adaptive state feedback control law is constructed such that the estimate of the unknown coefficient is bounded and the closed‐loop PDE is asymptotically stable in the sense of spatial ℋ1$$ {\mathscr{H}}^1 $$ norm if a sufficient condition given in terms of space‐time varying linear matrix inequalities (LMIs) is fulfilled for the estimated coefficient and the control gains. Both analytical and numerical approaches are proposed to construct a feasible solution to the space‐time varying LMI problem. With the aid of the semigroup theory, the well‐posedness and regularity of the closed‐loop PDE is also analyzed. Moreover, two extensions of the proposed adaptive control scheme are discussed: the PDE in N$$ N $$‐D space and the PDE with unknown diffusion and reaction coefficients. Finally, numerical simulation results are presented to support the proposed spatiotemporal adaptive control design.
A Pd‐catalyzed hydrophosphinylation of alkyl and aryl‐oxyallenes with phosphine oxides has been developed for the efficient and rapid construction of a family of chiral allylic phosphine oxides with ...a diverse range of functional groups. This methodology was further applied in the facile construction of chiral 2H‐chromene and later stage functionalization of cholesterol.
A highly efficient, versatile and atom‐economic protocol to chiral allylic phosphine oxides is demonstrated via palladium‐catalyzed asymmetric hydrophosphinylation of allenes with phosphine oxides. A family of chiral allylic phosphine oxides with a diverse range of functional groups were obtained in high yield (up to 99 %) and enantioselectivities (up to 99 % ee).
Concerns regarding microplastics pollution and their potential to concentrate and transport organic contaminants in aquatic environments are growing in recent years. Sorption of organic chemicals by ...microplastics may affect the distribution and bioavailability of the chemicals. Here sorption process of pyrene (Pyr), a frequently encountered polycyclic aromatic hydrocarbon in aquatic environments, on three types of mass-produced plastic particles (high-density polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC)), was investigated by comparative analysis of different sorption kinetic and isotherm models. Optimum kinetic and isotherm models were predicted by the linear least-squares regression method. The pseudo-second-order kinetic model was more appropriate in describing the entire sorption process (R2 > 0.99). Sorption rates of Pyr onto microplastics were mainly controlled by intraparticle diffusion. PE exhibited the highest affinity for Pyr, followed by PS and PVC. The sorption equilibrium data were best fitted to the Langmuir isotherm (R2 > 0.99), indicating monolayer coverage of Pyr onto the microplastics.
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•Sorption kinetics and isotherms of pyrene onto microplastics were studied.•Sorption of pyrene followed the order of PE > PS > PVC.•Pseudo-second-order model was appropriate to describe the sorption kinetics.•Sorption equilibrium data were best fitted to the Langmuir model.
We investigated microplastic pollution levels in surface waters and sediments from the Three Gorges Reservoir (TGR). The TGR is the largest reservoir in China and is located across the Chongqing ...municipality and Hubei Province. Microplastic abundance in the surface water ranged from 1597 to 12,611n/m3 and in the sediments was 25 to 300n/kg wet weight (ww). In the surface waters, the contamination was more serious in urban areas, and in the sediments, countrysides were the most heavily polluted areas. Fibers were the most abundant microplastics, the dominant color was transparent, and small-sized particles were predominant. Of all the microplastics identified by micro-Raman spectroscopy, polystyrene was the most common type (38.5%) followed by polypropylene (29.4%) and polyethylene (21%). Compared with low-density microplastics, the high-density ones were more likely to be deposited from the water into the sediment. Several contaminants adsorbed by microplastics, such as organic solvents and pharmaceutical intermediates, were observed and qualitatively analyzed by Raman spectroscopy. The results of this study could provide valuable background information for microplastic pollution in the TGR.
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•Microplastics were studied in the largest reservoir from China.•Residential and sewage treatment plants affected microplastic concentrations.•There was no significant correlation between microplastic concentrations in each sampling site.•The high-densitiy microplastics were more likely to deposit in the sediment.
Enormous efforts have been devoted to the reduction of carbon dioxide (CO2) by utilizing various driving forces, such as heat, electricity, and radiation. However, the efficient reduction of CO2 is ...still challenging because of sluggish kinetics. Recent pioneering studies from several groups, including us, have demonstrated that the coupling of solar energy and thermal energy offers a novel and promising strategy to promote the activity and/or manipulate selectivity in CO2 reduction. Herein, we clarify the definition and principles of coupling solar energy and thermal energy, and comprehensively review the status and prospects of CO2 reduction by coupling solar energy and thermal energy. Catalyst design, reactor configuration, photo‐mediated activity/selectivity, and mechanism studies in photo‐thermo CO2 reduction will be emphasized. The aim of this Review is to promote understanding towards CO2 activation and provide guidelines for the design of new catalysts for the efficient reduction of CO2.
A bundle of energy: The coupling of solar energy and thermal energy is a promising strategy to mediate the activity and/or selectivity of CO2 reduction. The status and prospects of this topic are reviewed, with the aim of providing guidelines for the design of new catalysts.
Microplastics pollution in aquatic ecosystems has aroused increasing global concern, leading to an explosive growth of studies regarding microplastics published in the past few years. To date, there ...is still a lack of standardized methodologies used for the detection of microplastics within environmental samples, thus hampering comparison of the reported data. This review summarizes the currently used methodologies for sampling, extracting and identifying microplastics in three kinds of aquatic environmental matrices (water, sediment and aquatic biota) and includes a critical discussion of the advantages and limitations of these methodologies. The quality control and quality assurance measures taken to reduce background contamination and validate analytical methods are also discussed. Finally, this review highlights the current challenges and gives suggestions for the future research.
•Microplastics have been considered as an emerging environmental pollutant.•Methods used for sampling, handling and identifying microplastics were assessed.•Quality assurance and quality control were discussed.•Current challenges and suggestions for future studies were highlighted.
Oxygen‐redox of layer‐structured metal‐oxide cathodes has drawn great attention as an effective approach to break through the bottleneck of their capacity limit. However, reversible oxygen‐redox can ...only be obtained in the high‐voltage region (usually over 3.5 V) in current metal‐oxide cathodes. Here, we realize reversible oxygen‐redox in a wide voltage range of 1.5–4.5 V in a P2‐layered Na0.7Mg0.2Fe0.2Mn0.6□0.2O2 cathode material, where intrinsic vacancies are located in transition‐metal (TM) sites and Mg‐ions are located in Na sites. Mg‐ions in the Na layer serve as “pillars” to stabilize the layered structure during electrochemical cycling, especially in the high‐voltage region. Intrinsic vacancies in the TM layer create the local configurations of “□–O–□”, “Na–O–□” and “Mg–O–□” to trigger oxygen‐redox in the whole voltage range of charge–discharge. Time‐resolved techniques demonstrate that the P2 phase is well maintained in a wide potential window range of 1.5–4.5 V even at 10 C. It is revealed that charge compensation from Mn‐ and O‐ions contributes to the whole voltage range of 1.5–4.5 V, while the redox of Fe‐ions only contributes to the high‐voltage region of 3.0–4.5 V. The orphaned electrons in the nonbonding 2p orbitals of O that point toward TM‐vacancy sites are responsible for reversible oxygen‐redox, and Mg‐ions in Na sites suppress oxygen release effectively.
Na0.7Mg0.2Fe0.2Mn0.6□0.2O2 with native transitional metal (TM) vacancies is designed as a novel cathode material for sodium‐ion batteries. The TM vacancies lead to nonbonding O 2p orbitals in this material, pointing toward these vacancies triggering reversible whole‐voltage‐range oxygen redox during charge and discharge processes. This work provides new ideals for design of cathode materials in anionic redox chemistry.
The intrinsic zinc dendrite growth aggravated by the uneven electric field at the Zn anode surface and the water‐induced parasitic reactions have largely impeded rechargeable aqueous zinc‐ion ...batteries for the practical applications in large‐scale energy storage. Here, an effective strategy is proposed to manipulate Zn deposition and simultaneously prevent the generation of insulating by‐products (Zn4SO4(OH)6·xH2O) for improved plating/stripping on Zn anodes by the addition of a nontoxic electrolyte additive, β‐cyclodextrin (β‐CD). The simulation results indicate that β‐CD molecules prefer to adsorb horizontally on Zn (002) plane, regulating the diffusion pathways and deposition sites of Zn2+ for the preferred Zn deposition along (002) plane without dendrite formation and inhibiting the H2 generation and the formation of Zn4SO4(OH)6·xH2O by facilitating desolvation of Zn(H2O)62+. Consequently, an ultra‐long stable cycling up to 1700 h at a high current density of 4 mA cm−2 can be achieved by the addition of β‐CD, 17 times that of the pure ZnSO4 electrolyte and the remarkable stability is also maintained under harsh test condition (40 mA cm−2, 20 mAh cm−2). This study highlights the important role of β‐CD in engineering the interfacial stability during Zn plating/stripping for high‐performing aqueous batteries.
β‐Cyclodextrin (β‐CD) additive with a special cavity structure is developed to regulate the deposition orientation of zinc ions and inhibit the parasitic reaction at the same time, resulting in highly reversible and stable Zn anode. Herein, the Zn//Zn cells with β‐CD display remarkable stability at different current densities ranging from 4 to 40 mA cm−2, much better than that in pure ZnSO4 electrolyte. This study demonstrates the remarkable effect of β‐CD on stabilizing the Zn anodes and provides insight into the design of versatile electrolytes for aqueous ion batteries.
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