Latest ArticlesHerein, we report the facile synthesis of a highly strained hexabenzocoronene-containing carbon nanoring, cyclo[4]-paraphenylene[2]-2,11-hexabenzocoronenylene ([4,2]CPHBC), as the segment of a [10,10] single-walled carbon nanotube ([10,10]SWNT). [4,2]CPHBC was synthesized based on the platinum-mediated assembly of diborylbiphenyl and diborylhexabenzocoronene, forming a tetranuclear platinum complex, followed by reductive elimination. This nanoring molecule was confirmed by NMR and HR-MS, and its photophysical properties were studied using steady-state and time-resolved spectroscopies. Moreover, the selective supramolecular host-guest interaction between [4,2]CPHBC and C60 was also investigated.
The detrimental "shuttle effect" of lithium polysulfides (LiPSs) together with sluggish multi-order reaction kinetics are the main drawbacks hindering lithium-sulfur (Li-S) batteries from commercial success. Here, we first propose the implementability of layered rare-earth hydroxides (LREHs) in Li-S batteries to optimize electrochemical performance. In this work, a two-dimensional (2D) rare-earth-based composite constructed by the layered gadolinium hydroxy chloride [Gd2(OH)5(H2O)]Cl nanoplates (LGdH NPs) and graphene oxide (GO) was designed as a sulfur immobilizer for Li-S batteries. Combining the experimental results and density functional theory (DFT) calculations, it is revealed that the LGdH@GO composite not only provides a strong anchoring of the intermediates during cycling, but also acts as an effective catalyst to accelerate the liquid-solid conversion of polysulfides. The Li-S batteries assembled by LGdH@GO modified separators delivered a superior rate performance with a specific capacity of 605.34 mAh/g at 5 C, as well as excellent cycle stability with a decay rate of 0.087% over 500 cycles at 2 C. This study provided a deep understanding of the mechanism to suppress the "shuttle effect" by the LREHs, and a guide to design effective functional interlayers for high-performance Li-S batteries with excellent electrocatalytic activity.
Targeted construction of new covalent organic frameworks (COFs) with specific purposes and rationalities to build colorimetric assay platform for environmental pollutant monitoring have attracted increasing interest. However, it is still challenging due to lack of available coordination sites inside COFs pores and only a slight bonding ability for anchoring metal. In this work, a two-dimensional (2D) COFs (termed as Tz-COF) with high crystallinity, excellent chemical stability, and abundant sulfur coordination in its skeletons was synthesized and used for the confined growth of Au NPs. It was found that the Au NPs showed significant dispersibility for the support of Tz-COF. The proposed Tz-COF@Au NPs possessed outstanding Hg2+-activated peroxidase-like activity benefited from physicochemical properties of gold amalgam and synergistic effect between COFs and Au NPs to oxidize chromogenic substrate. Based on highly efficient activity and distinctive color evolution, the strategy for detecting Hg2+ was developed and successfully applied to determine the content of Hg2+ in real environmental samples. This work manifests that a potential strategy to establish a colorimetric assay platform for environmental pollutant monitoring based on the targeted manufacturing of novel COFs with specific functions.
Hydroxylation of steroid core is critical to the synthesis of steroid drugs. Direct sp3 C–H hydroxylation is challenging through chemical catalysis, alternatively, fungal biotransformation offers a possible solution to this problem. However, mining and metabolic engineering of cytochrome P450 monooxygenases (CYPs) is usually regarded as a more eco-friendly and efficient strategy. Herein, we report the mining and identification of a new steroid CYP (CYP68BE1) from Beauveria bassiana by transcriptomics, heterologous expression, in vivo and in vitro functional characterization. The catalytic promiscuity of CYP68BE1 was explored, and CYP68BE1 showed promiscuously and catalytically versatile, which is qualified for monohydroxylation on C11α, C1α, C6β and dihydroxylation on C1β, 11α and C6β, 11α of six steroids, leading to the production of key steroid intermediates required in the industrial synthesis of some indispensable steroid drugs. Molecular dynamics simulations were performed, revealing the molecular basis of different binding orientations of CYP68BE1 with different substrates. The discovery of CYP68BE1 offers a promising biocatalyst for enriching the steroid structural and functional diversity, which also can be applied to biosynthesize valuable steroid drug intermediates.
Borylation of 1,3-enynes with bis(boronate) compounds often ends up with the formation of hydroborylated products, leaving the diborylation of 1,3-enynes for the formation of 1,4-diborylated allenes to be challenging. Herein, a copper-catalyzed chemo-, regio-, and stereo-selective diborylation of 1,3-enynes for the efficient construction of 1,4-diborylated allenes under base-free conditions was reported. A wide range of 1,3-enynes bearing various functional groups can participant in the reaction and afforded the corresponding 1,4-diborylated allenes in good to excellent yields, which was enabled by the protocol of Bpin to BF3K conversion. the borylcopper species was supposed to selectively attack the C–C triple bond of the 1,3-enynes.
An efficient synthesis of the electrophilic reagent, S-(1,3-dioxoisoindolin-2-yl)O,O-diethyl phosphorothioate (SDDP) is described. Moreover, the synthetic applications of SDDP wherein the transfer of the SP(O)(OEt)2 moiety occurs were investigated. In this manner, SDDP underwent facile SP(O)(OEt)2 transfer with electron-rich substrates such as ketones, indoles, and thiols to form α-phosphorothiolated ketones, 3-phosphorothiolated indoles and S-phosphorothiolated thioethers, respectively.
Thin-film composite (TFC) reverse osmosis (RO) membranes have attracted considerable attention in water treatment and desalination processes due to their specific separation advantages. Nevertheless, the trade-off effect between water flux and salt rejection poses huge challenges to further improvement in TFC RO membrane performance. Numerous research works have been dedicated to optimizing membrane fabrication and modification for addressing this issue. In the meantime, several reviews summarized these approaches. However, the existing reviews seldom analyzed these methods from a theoretical perspective and thus failed to offer effective optimization directions for the RO process from the root cause. In this review, we first propose a mass transfer model to facilitate a better understanding of the entire process of how water and solute permeate through RO membranes in detail, namely the migration process outside the membrane, the dissolution process on the membrane surface, and the diffusion process within the membrane. Thereafter, the water and salt mass transfer behaviors obtained from model deduction are comprehensively analyzed to provide potential guidelines for alleviating the trade-off effect between water flux and salt rejection in the RO process. Finally, inspired by the theoretical analysis and the accurate identification of existing bottlenecks, several promising strategies for both regulating RO membranes and optimizing operational conditions are proposed to further exploit the potential of RO membrane performance. This review is expected to guide the development of high-performance RO membranes from a mass transfer theory standpoint.
The fascinating chemical structure and broad application prospect of Keggin-type polyoxometalates (POMs) have attracted many chemists to explore and discover continuously. Unlike the traditional Keggin, larger metal atomic radius, higher metal coordinated numbers, lower metal valence states and other features allow the group IVB metal-based Keggin (IVB-Keggin) more space and unknown in terms of structure and performance. Herein, density functional theory (DFT) calculations were performed to explore the influences including cores, shells, caps, and terminal ligands, et al. on IVB-Keggin, and analyze the possibility of novel structure synthesis. From the perspective of multi-layer onion-like clusters, molecular energy level, host-guest interaction energy, surface charge and covalent bond polarity can be further adjusted to achieve the oriented design of functional IVB-Keggin. These insights are expected to provide theoretical support for experimental synthesis, opening a new perspective to understand the growth of Keggin.
Saccharides are a sort of ubiquitous and vital molecules within the whole life. However, the application of saccharides analysis with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is restricted by their low ionization efficiency and the instability of the sialic acid fraction. Derivatization strategy based on nonreductive amination provides a good solution, however, this is often time consuming and may result in sample loss due to removal of excessive derivatization reagents. Herein, hydralazine (HZN) was utilized as a reactive matrix for labeling reducing saccharides directly on MALDI target which eliminated tedious sample preparation and avoided sample loss. After optimization, effective and reproducible on-MALDI-target derivatization of neutral and acidic saccharides was achieved in both positive and negative modes. Compared with 2,5-dihydroxybenzoic acid (DHB) and 9-aminoacridine (9-AA), HZN improved the detection sensitivity of reducing saccharides and provided more abundant fragment ions in MS/MS analysis. Moreover, 26 kinds of neutral glycans and 5 kinds of sialic glycans were identified from ovalbumin (OVA) and bovine fetuin, respectively. Combined with the statistical models, this strategy could be used to distinguish and predict samples of 6 brands of beer, and discriminate 2 kinds of beer fermentation modes. In addition, HZN was applied for quantitative analysis of glucose in urine samples, and the obtained urine glucose concentrations of diabetic patients were consistent with the clinical test results, showing the potential of qualitative and quantitative analysis of reducing saccharides in complex samples.
Grain boundary (GB), as a kind of lattice defect, widely exists in two-dimensional transition metal dichalcogenides (2D TMDs), which has complex and diverse influences on the physical/chemical properties of 2D TMDs. GBs are universally considered to be a double-edged sword, although some electrical and mechanical properties of 2D TMDs would be adversely affected leading to the reduced overall quality, certain structure-oriented applications could be realized based on its unique properties. In this review, we first detailed the atomic structure characteristics of GBs and the corresponding techniques, then we systematically summarized the methods of introducing GBs into 2D TMDs. Next, we expounded unique electrical, mechanical, and chemical properties of the GBs in 2D TMDs and clarified its internal relationship with the atomic structure. Moreover, the application of GB structure in hydrogen evolution reaction (HER) is also discussed. In the end, we make a conclusion and put forward outlooks, hoping to further promote the basic research of GB and boost the wide application of 2D TMDs.
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