Latest ArticlesThe designed synthesis of chiral covalent organic frameworks (COFs) featuring intriguing properties is fairly scant and remains a daunting synthetic challenge. Here we develop a de novo synthesis of an enantiomeric pair of 2D hydroxyl-functionalized hydrazone-linked chiral COFs, (S)- and (R)-HthBta-OH COFs, using enantiopure 2, 5-bis(2-hydroxypropoxy)terephthalohydrazide (Hth) as monomers. The formation process of hydroxyl-functionalized chiral COFs was monitored using rigorous time-dependent PXRD, vibrational circular dichroism (VCD), and electronic circular dichroism (ECD) studies. Remarkably, VCD spectra indicated a unique chiral signal inversion from the positive Cotton effect of (S)-Hth monomer to the negative Cotton effect of (S)-HthBta-OH COF, which has never been reported in chiral COFs. Moreover, two unprecedented carboxyl-functionalized chiral COFs, (S)- and (R)-HthBta-COOH, were constructed by a post-synthetic modification of the corresponding hydroxyl chiral COFs with succinic anhydride. Notably, carboxyl-functionalized COFs retained homochirality and crystallinity without linker racemization and structural collapse after the chemical modification due to the chemically robust nature of pristine hydrazone-linked chiral COFs.
Fe3O4 is considered as a promising electrode material for lithium-ion batteries (LIBs) due to its low cost and high theoretical capacity (928 mAh/g). Nevertheless, the huge volume expansion and poor conductivity seriously hamper its practical applications. In this study, we use a facile hydrothermal reaction together with a post heat treatment to construct the three-dimensional heterostructured composite (Fe3O4/rGO) inwhich reduced graphene oxide sheets wraped the Fe3O4 submicron cubes as the conductive network. The electric conduction and electrode kinetics of lithium ion insertion/ extraction reaction of the composite is enhanced due to the assist of conductive rGO, and thus the Li-storage performance is obviously improved. The composite exhibits a reversible charge capacity of 772.1 mAh/g at the current density of 0.1 A/g, and the capacity retention reaches 70.3% after 400 cycles at 0.5 A/g, demonstrating obviously higher specific capacity and rate capability over the Fe3O4 submicron cubes without rGO, and much superior cycling stability to the parent Fe2O3 submicron cubes without rGO. On the other hand, as a synergic conductive carbon support, the flexible rGO plays an important role in buffering the large volume change during the repeated discharge/charge cycling.
Hollow nanostructures have attracted increasing research interest in hydrogen evolution reaction owing to their unique structural features. Herein, Ni–Co mixed metal phosphide hollow and porous polyhedrons was successfully composited (expressed as NiCoP). Benefiting from the synergistic effects of ZIF-67 by doping Ni elements and the well-defined hollow and porous structure, the as-synthesized NiCoP hollow and porous polyhedrons exhibit better electrochemical properties and mechanical stability for hydrogen evolution reaction over a pH-universal range, with a small Tafel slopes of 72, 101, 176 mV/dec, and a low overpotential of 82, 102, 261 mV at a current density of 10 mA/cm2 in 0.5 mol/L H2SO4, 1 mol/L KOH and 1 mol/L phosphate buffer solution (PBS). This general strategy can also be applied to fabricate other hollow cobalt-based phosphides and MOFs-derived materials for HER.
All-solid-state Li metal battery has been regarded as a promising battery technology due to its high energy density based on the high capacity of lithium metal anode and high safety based on the all solid state electrolyte without inflammable solvent. However, challenges still exist mainly in the poor contact and unstable interface between electrolyte and electrodes. Herein, we demonstrate an asymmetric design of the composite polymer electrolyte with two different layers to overcome the interface issues at both the cathode and the anode side simultaneously. At the cathode side, the polypropylene carbonate layer has enough viscosity and flexibility to reduce the inter-facial resistance, while at the Li anode side, the polyethylene oxide layer modified with hexagonal boron nitride has high mechanical strength to suppress the Li dendrite growth. Owing to the synergetic effect between different components, the as-prepared double layer composite polymer electrolyte demonstrates a large electrochemical window of 5.17 V, a high ionic conductivity of 6.1×10-4 S/cm, and a transference number of 0.56, featuring excellent ion transport kinetics and good chemical stability. All-solid-state Li metal battery assembled with LiFePO4 cathode and Li anode delivers a high capacity of 150.9 mAh/g at 25 ℃ and 0.1 C-rate, showing great potential for practical applications.
The cascade reactions of alkyl α-diazoesters and ynones using Al(OTf)3 as the catalyst are described. A series of 4-substituted pyrazoles were obtained via [3 + 2] cycloaddition, 1, 5-ester shift, 1, 3-H shift, and N—H insertion process. Deuterium labelling experiments, kinetic studies and control experiments were carried out for the rationalization of the mechanism.
A convenient and regioselective sulfonylation/cyclization of 1,6-enynes with arylazo sulfones has been developed to access a series of sulfonylated γ-butyrolactams. The present reaction could be efficiently conducted under catalyst- and additive-free conditions, in which C—S and C—C bonds were selectively constructed in one-pot procedure.
Both nitrogen-doping feature and pore structure are critical factors for developing nitrogen-doped carbons based catalysts with a high performance toward oxygen reduction reaction (ORR). Herein, a simple one-step CVD of acetylene and acetonitrile vapor method using silanized SBA-15 as a template has been developed to synthesize an ordered porous carbon (OPC) with dual nitrogen-doped interfaces. The optimized sample as prepared with the CVD of 4 h at 750 ℃ contains two types of ordered mesopores that one type is the ordered cylindrical pores inheriting from the pores of SBA-15 and has a pore width of 4.0~5.0 nm, the other type is the ordered quasi-hexagonal pores with a width of 3.0~4.0 nm produced by etching the pore walls of SBA-15. These two types of pores whose pore walls are built by the nitrogen doped carbon layers resulted by the CVD and thus it actually makes the dual nitrogen-doped interfaced OPC (DN-OPC). Meanwhile, DN-OPC contains a few of micropores and a large SSA of 1430 m2/g. This dual-ordered pores and dual nitrogen-doped interfaces cannot only facilitate mass transport but also utilize the active sites of DN-OPC for ORR. Therefore, as metal-free ORR catalyst, DN-OPC exhibits a good activity close to commercial Pt/C catalyst, and an excellent durability and methanol tolerance.
Metal-free direct α-C(sp3)—H intramolecular cyclization of 2-alkylthiobenzoic acid in the presence of Selectfluor is described. This novel strategy provides a facile and efficient method to access important 1, 3-benzooxathiin-4-one derivatives with good functional groups tolerance and yields.
3D highly ordered silver nanoparticles (AgNPs) coated silica photonic crystal beads (Ag/SPCBs) were prepared and exploited as a novel surface enhanced Raman scattering (SERS) substrate. The monodisperse and size-controlled SPCBs were prepared via self-assembly of silica nanoparticles process using a simple microfluidic device. Then the Ag/SPCBs were easily obtained by in situ growth of AgNPs onto the NH2-modified SPCBs. Field emitting scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) were used to characterize the Ag/SPCBs. The effect of silica nanoparticle size and AgNO3 concentration on the SERS performance of the resultant Ag/SPCBs substrate were discussed in detail. The results indicate that the Ag/SPCBs have highest SERS signals when silica nanoparticle size is 250 nm and AgNO3 concentration is 0.8 mg/mL. Using malachite green (MG) as model analyte, the Ag/SPCBs substrate displayed a high sensitivity and a wide linear range for MG. The well-designed Ag/SPCBs show high uniformity and excellent reproducibility, and can be used as an effective SERS substrate for sensitive assay application.
Cobalt phosphide (CoP) is a promising anode candidate for lithium-ion batteries (LIBs) due to its high specific capacity and low working potential. However, the poor cycling stability and rate performance, caused by low electrical conductivity and huge volume variation, impede the further practical application of CoP anode materials. Herein, we report an integrated binder-free electrode featuring needle-like CoP arrays grown on carbon fiber cloth (CC) for efficient lithium storage. The as-prepared CoP/CC electrode integrates the advantages of 1D needle-like CoP arrays for efficient electrolyte wettability and fast charge transportation, and 3D CC substrate for superior mechanical stability, flexibility and high conductivity. As a result, the CoP/CC electrode delivers an initial specific capacity of 1283 mAh/g and initial Coulombic effeciencies of 85.4%, which are much higher than that of conventional CoP electrode. Notably, the CoP/CC electrode shows outstanding cycling performance up to 400 cycles at 0.5 A/cm2 and excellent rate performance with a discharge capacity of 549 mAh/g even at 5 A/cm2. This work demonstrates the great potential of integrated CoP/CC hybrid as efficient bind-free and freestanding electrode for LIBs and future flexible electronic devices.
No. 86 Xueyuan South Road, Haidian District, Beijing
010-62662699(Operation and Technical Support)
qkjq@cast.org.cn
Copyright © 2025 China Association for Science and Technology. All rights reserved. For all open access content, the relevant licensing terms apply.
Sponsored by the Office of the Leading Group for Cybersecurity and Informatization of CAST, and supported by Science and Technology Review Publishing House
