Latest ArticlesA photoinduced reaction of potassium alkyltrifluoroborates, sulfur dioxide, and para-quinone methides under visible light irradiation at room temperature is developed, giving rise to diarylmethyl alkylsulfones in moderate to good yields. This reaction works well under photocatalysis with a broad substrate scope by using DABCO·(SO2)2 as the source of sulfur dioxide. Mechanistic study shows that this transformation is initiated by alkyl radicals generated in situ from potassium alkyltrifluoroborates in the presence of photocatalyst. The subsequent insertion of sulfur dioxide and radical 1, 6-addition of para-quinone methides with alkylsulfonyl radical intermediates afford the corresponding diarylmethyl alkylsulfones.
The mixture of p-(methoxy)calix[n]arenes (n = 6, 7 or 8) was prepared in one step from p-methoxyphenol under basic conditions, and their fully methylated derivatives p-(dimethyloxy)calix[n]arenes (n = 6, 7 or 8) were also prepared and purified by column chromatography to indentify their structures. In this process, the single crystal of p-(dimethyloxy)calix[7]arene was obtained and its structure was confirmed. The proportion of p-(methoxy)calix[6]-, [7]- and [8]-arenes in the mixture obtained from the reaction was investigated under different reaction conditions, and p-(methoxy)calix[6]- and [8]-arenes could be separated from the mixture by solvent extraction. In addition, the host-guest interaction of p-(dimethyloxy)calix[6]arene with methyl-4, 4′-bipyridinium hexafluorophosphate in organic solvents was investigated.
A condition-controlled strategy for selectively synthesis of 2-acylbenzothiazoles and bibenzo[b][1, 4]thiazines from aryl methyl ketones and disulfanediyldianilines was realized using I2/DMSO or I2/MeCN systems, respectively. The desired products were synthesized in only 15 min with moderate to excellent yields (50%-90%) under microwave-assisted, metal-free conditions. The strategy provides a great advantage for selective synthetic applications in the efficient synthesis of benzothiazoles and bibenzothiazines heterocycle compounds.
The angle dependence of photonic crystals (PCs) dramatically limits their practical applications in the colorimetrical sensing of humidity and volatile organic compound (VOC) vapors. In addition, it is challenging for inverse opal PCs to colorimetrically distinguish between vapors with similar refractive indices. Different from the mechanism of PC-based sensors, here, we report an angle-independent polyacrylamide (PAAm) organogel structural color film based on the mechanisms of retroreflection, total internal reflection (TIR) and interference with a shape similar to a single-sided "egg waffle". During the process of responding to humidity and VOC vapors, the color of the film remains angle-independent in the normal angle range of 0° to 45° under coaxial illumination and observation conditions. At the same time, the film can colorimetrically distinguish between vapors with similar refractive indices, such as methanol and ethanol, which is mainly due to the differences in their polarity and solubility parameters. The film shows good stability, reversibility and selectivity when exposed to vapors. A colorimetric sensor with a new response mechanism is proposed and has the potential to effectively distinguish between vapors with similar refractive indices. Furthermore, this responsive retroreflective structural color film (RRSCF) provides a universal strategy to develop targeted angle-independent structural color sensors by selecting optimized materials.
Hydrogen isotope separation is a challenging task due to their similar properties. Herein, based on the chemical affinity quantum sieve (CAQS) effect, the D2/H2 separation performance of M2(m-dobdc) (M = Co, Ni, Mg, Mn; m-dobdc4− = 4,6-dioxido-1,3-benzenedicarboxylate), a series of honeycomb-shaped MOFs with high stability and abundant open metal sites, are studied by gases sorption and breakthrough experiments, in which two critical factors, gas uptake and adsorption enthalpy, are taken into consideration. Among these MOFs, Co2(m-dobdc) exhibits the longest D2 retention time of 180 min/g (H2/D2/Ne: 1/1/98) at 77 K because of its second-highest adsorption enthalpy (10.7 kJ/mol for H2 and 11.8 kJ/mol for D2) and the best sorption capacity (5.22 mmol/g for H2 and 5.49 mmol/g for D2) under low pressure of 1 kPa and 77 K), which make it a promising material for industrial hydrogen isotope separation. Moreover, the results indicate that H2 and D2 capacities under low pressure (about 1 kPa) dominate the final D2/H2 separation property of MOFs.
Surface oxidized iron-nickel nanorods coupling with reduced graphene architectures (FeNi-O-rGA) are successfully constructed via hydrothermal, freeze-drying, and thermal activation approaches. The hierarchical structure can provide lots of pathways for fast ion diffusion and charge transfer, and expose abundant catalytic sites. Meanwhile, the activity of FeNi-O-rGA is boosted by the optimized metal-oxygen bond strength in FeNi3 alloys. Partial oxidized FeNi nanorods are strongly coupled with rGA by the formation of metal-O-C bonds, which can impede the aggregation of FeNi3 alloys and increase the utilization of active sites. The special structure and partially oxidized FeNi nanorods for FeNi-O-rGA can result in excellent OER activity and catalytic stability. Only 215 mV of overpotential is required to drive the current density of 10 mA/cm2 as well as the Tafel slope of 50.9 mV/dec in 1 mol/L KOH. The change of surface chemistry of FeNi-O-rGA is confirmed by XPS after the OER test, which indicates the highly catalytic stability of FeNi-O-rGA due to the formation of intermediate metal oxyhydroxide.
Crystalline engineering and heterostructure have attracted much attention as effective strategies to improve the electrocatalytic activity for hydrogen evolution reaction (HER). In this study, a new heterostructure catalyst (Ru/RuS2@N-rGO) with low crystallinity was fabricated by a simple and low-temperature method for HER in alkaline solution, applying the Na2SO4 as S source and polypyrrole as N source. Optimizing through the controllable crystalline engineering and composition ratio of Ru and RuS2, the Ru/RuS2@N-rGO heterocatalyst at the calcining 500 ℃ revealed highly efficient HER activity with overpotential 18 mV at a current density 10 mA/cm2 and remarkable stability for 24 h in 1.0 mol/L KOH. This work provides a facile and effective method in designing advanced electrocatalysts for HER in the alkaline electrolytes by synergistically structural and component modulations.
The trade-off between the electrochemical performance and mechanical strength is still a challenge for Ti3C2Tx free-standing electrode. Herein, a facile approach was proposed to fabricate a Microfibrillated cellulose@Ti3C2Tx (MFC@Ti3C2Tx) self-assembled microgel film by means of hydrogen bonding linkage. Benefiting from the rich hydroxyl groups on the MFC, the Ti3C2Tx nanosheets coated on the MFC in a time scale of minutes (within 1 min) instead of hours. The ultralong 1D frame of MFC effectively mitigated the re-aggregation of Ti3C2Tx nanosheet. The fluffy MFC@Ti3C2Tx film structure and the constructed 1D/2D conducting Ti3C2Tx pathways in horizontal and vertical directions endowed the fast ion transport of the electrolytes and the improved accessibility to the Ti3C2Tx surface. As a result, the freestanding MFC@Ti3C2Tx microgel film delivered a high specific capacitance of 451 F/g. And the rate performance was increased to 71% from the 64% of that of pristine Ti3C2Tx film. Furthermore, the tensile strength of MFC@Ti3C2Tx film was also promoted to 46.3 MPa, 3 folds of that of the pristine Ti3C2Tx film, due to the high strength of MFC and the hydrogen bonding effect.
A hydrophobic carbon dots (Glc-OCDs) derived from octadecylamine and glucose were successfully synthesized for the first time and then grafted onto the porous silica surface by the "Nano-on-Micro" strategy, which was served as a new stationary phase (Sil-Glc-OCDs) for reversed-phase liquid chromatography. The structure of this stationary phase was carefully verified by laser scanning confocal microscope, Fourier transform infrared spectrometry, elemental analysis, contact angle measurement, etc. Several analytes including seven polycyclic aromatic hydrocarbons, eight alkylbenzenes, eight phenols and seven sulfonamides can be well separated on this stationary phase. Better separation performance for certain analytes over commercial C18 column was obtained. Interestingly, this stationary phase exhibited excellent chromatographic selectivity in the separation of the isomers of tert‑butylbenzene, sec‑butylbenzene, isobutylbenzene and n-butylbenzene. In addition, this new Sil-Glc-OCDs column was also applied for detection of calycosin-7-glucoside, ononin, calycosin, formononetin, genistein and isorhamnetin in the extract of Radix Astragali, which were found that the concentration was 0.15 g/L, 0.088 g/L, 0.14 g/L, 0.086 g/L, 0.18 g/L and 0.29 g/L, respectively. We believe that this CDs-grafted silica materials are promising for chromatographic separation.
The existence of many anions in wastewater reduces the removal efficiency of phosphate by adsorbents under realistic conditions. Facing this challenge, the study reports on an insistent and stable composite adsorbent of molybdate complexes Fe-(MoOx) embedded in a macroporous anion exchange resin (D-201). [Fe(MoOx)]-D-201 shows 93.7% adsorption capacity (28.3 mg/g) for phosphate even when the molar concentration of coexisting ions is 5 times higher than phosphate. The capacity of adsorbent is maintained more than 84.2% after five regeneration cycles to remove phosphate in the wastewater containing coexisting ions. The ability of highly selective removal of phosphate is maintained during the regeneration cycles explained by the change of the binding of molybdate clusters with phosphate, which is due to the different structures of molybdate clusters depending on various pH. In general, this work puts forward a new idea for the development of phosphorus removal adsorbents for the treatment of wastewater containing coexisting ions.
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