Latest ArticlesGraphene oxide (GO) with one-atom-thick exhibit remarkable molecule sieving properties, but its low permeance flux renders it difficult to be applied in practice as a high-permeance separation membrane. In this study, we design complex membrane from covalently crosslinked GO, polydopamine (PDA), and 3-aminopropytriethoxysilane (APTES) as building blocks to fabricate the high-permeance GO-based membrane via the vacuum filtration method. A branched crosslinking product (PDA/APTES) working as a clamp grasped the hydrophilic functional groups (hydroxyl, epoxy, carboxyl) on GO for improving the GO membrane flux. The interlayer structure of the GO membrane was optimized according to the crosslinker concentration, reaction time, initial pH, and temperature for RGO/PDA/APTES (RGPA) in this study. At the optimized reaction conditions including the crosslinker concentration of 1.4 mL/L, the temperature of 80 ℃, the time of 16 h, and the initial pH of 8.5 for RGPA mixture, the interlayer gallery of RGPA membrane was effectively tunes, endowing high flux ranging from 11.98 L m−2 h−1 to 1823.97 L m−2 h−1. Besides, the RGPA membrane ensured the high rejections to dye solutions such as methylene blue (MB) (> 99%) and congo red (CR) (> 90%). Meanwhile, the superior reusable performance of the RGPA membrane was achieved, together with the rejections for MB and CR to 96.32% and 93.1% after 4 cycles, respectively. Also, the RGPA membrane possessed superior anti-fouling performances for bovine serum albumin (BSA) aqueous solution and excellent stabilities in harsh conditions (pH 3, 7 and 11). Grafting the crosslinker onto GO nanosheets exhibits the distinct advantages of achieving the high flux, high rejections to dyes, and superior reusable performance of membranes, posing a great application potential for membrane separation technology in wastewater treatment.
Boron/nitrogen-co-doped carbon (BCN) nanosheets decorated with Fe2O3 nanocrystals (Fe2O3–BCN) were cast on a glassy carbon electrode (GCE) and applied as an electrochemical sensor to effectively detect paraquat (PQ), a toxic herbicide, in aqueous environments. A linear experiment performed using square wave voltammetry (SWV) under optimized experimental conditions produced a decent linear relationship and a low detection limit (LOD) of 2.74 nmol/L (S/N = 3). Repeatability, reproducibility, stability, and interference experiments confirmed that the Fe2O3–BCN/GCE system exhibited decent electrochemical sensing performance for PQ molecules. Notably, the designed sensor showed high selectivity and a decent linear relationship with PQ concentration in natural water samples. To the best of our knowledge, this is the first study on the preparation of Fe2O3–BCN nanosheets for PQ detection. The proposed sensor can be employed as an effective alternative tool for distinguishing and processing PQ.
Photoredox-catalyzed hydrodifluoromethylation of alkenes has become an effective method to introduce difluoromethyl group into organic molecules. As the reported methods involve either photocatalysts or superstoichiometric amounts of additives, we herein describe a simple alternative without using photocatalyst or additive for the hydrodifluoromethylation of alkenes, through photoactivation of difluoromethyltriphenylphosphonium iodide salt. Mechanistic studies shed light on how the transformation takes place.
Chemical fixation of CO2 into C1 source, as a general approach, can effectively alleviate the emission of greenhouse gasses. Whereas, the challenge posed by the need for efficient catalysts with high catalytic active sites still exists. In this work, we reported a series of new hexavanadate clusters, [(C6H6ON)2(C2H8N2)2(CH3O)6V6IVO8] (V6–1), [(C6H6ON)2(C3H10N2)2(CH3O)6V6IVO8] (V6–2), [(C6H6ON)2(C6H14N2)2(CH3O)6V6IVO8] (V6–3) and [(C6H6ON)2(C4H11N2O)2(CH3O)4V6IVO8] (V6–4), assembled by 2-aminophenol and four different kinds of Lewis bases (LB), ethanediamine (en), 1,2-diaminopropane, 1,2-cyclohexanediamine and N-(2-hydroxyethyl)ethylenediamine (ben) together. Among them, the basic unit {V6} cluster featured Z-shaped configuration represents a brand-new example of hexanuclear vanadium clusters. Remarkably, the catalytic tests demonstrated that V6–1 as catalyst displays high catalytic activity in the cycloaddition for the CO2 fixation into cyclic carbonates by virtue of open V sites. As expected, for oxidative desulfurization of sulfides, V6–1 also exhibits satisfied catalytic effectiveness. Furthermore, the recycling test confirmed that catalyst V6–1 may be a bifunctional heterogeneous catalyst with great promise for both CO2 cycloaddition and oxidative desulfurization reactions.
Polyaniline-supported tungsten (W@PANI) was easily prepared by immersing polyaniline (PANI) in the aqueous solution of Na2WO4. It was found to be an efficient catalyst for oxidative deoximation reaction, the very important transformation for pharmaceutical industry. Besides the green features, the method employed very few of catalytic tungsten (0.048 mol% vs. oxime substrates), resulting in the high turnover numbers (TONs) of the catalyst (ca. 103 mol/mol) and the low metal residues in product (< 0.1 ppm). The reaction is applicable for a variety of substrates, including those containing heterocycles, which are key intermediates in medicine synthesis. It has also been successfully magnified to kilogram scale production to afford the desired carbonyl products smoothly.
Analytical chemistry plays an important role in the qualitive and quantitative analysis for molecules in the various circumstances, especially for the high-resolution analysis. The dual-comb spectroscopy (DCS) technology with the characteristics of high resolution, high sensitivity and instantaneous sampling exhibited a great potential in high-resolution in-situ spectral methods and has been active in the fields of spatial ranging, air composition analysis, reaction monitoring and so on. In this review, we will summarize the principle of DCS according to the different wavelength coverage and overview the applications of DCS in analytical chemistry.
Separator is supposed to own outstanding thermal stability, superior wettability and electrolyte uptake, which is essential for developing high-rate and safe lithium metal batteries (LMBs). However, commercial polyolefin separators possess poor wettability and limited electrolyte uptake. For addressing this issue, we put forward a composite separator to implement above functions by doping layered-silicate (talcum) into polyvinylidene fluoride (PVDF). With significant improvement of electrolyte absorption benefiting from the strong adsorption energy values (-1.64 ~ -1.70 eV) between talcum and the electrolyte in lithium metal batteries, PVDF/Talcum (PVDF/TM) composite separator owns a small contact angle and superior electrolyte uptake. PVDF/TM composite separator with 10 wt% talcum (T-10) owns a tiny contact angle of 8°, while those of polypropylene (PP) and PVDF are 48° and 20° with commercial electrolyte. Moreover, the addition of thermotolerant talcum endows the T-10 composite separator with great thermostability, whose thermal shrinkage is only 5.39% at 150 ℃ for 0.5 h. The cell with LiFeO4 cathode and the T-10 composite separator reaches 91.7 mAh/g in discharge capacity at 4.8 mA/cm2 (10 C), far superior to that with pure PVDF separator (56.3 mAh/g) and PP (51.4 mAh/g).
Photocatalytic selective transform native lignin into valuable chemicals is an attractive but challenging task. Herein, we report a mesoporous sulfur-doped carbon nitride (MSCN-0.5) which is prepared by a facile one-step thermal condensation strategy. It is highly active and selective for the cleavage Cα−Cβ bond in β−O−4 lignin model compound under visible light radiation at room temperature, achieving 99% substrate conversion and 98% Cα−Cβ bond cleavage selectivity. Mechanistic studies revealed that the Cβ−H bond of lignin model compounds activated by holes and generate key Cβ radical intermediates, further induced the Cα−Cβ bond cleavage by superoxide anion radicals (•O2−) to produce aromatic oxygenates. Waste Camellia oleifera shell (WCOS) was taken as a representative to further understand the reaction mechanisms on native lignin. 33.2 mg of monophenolic compounds (Vanillin accounted for 22% and Syringaldehyde for 34%) can be obtained by each gram of WCOS lignin, which is 2.5 times as that of the pristine carbon nitride. The present work offers useful guidance for designing metal-free heterogeneous photocatalysts for Cα−Cβ bond cleavage to harvest monophenolic compounds.
There is an urgent demand for tuning the selectivity and activity of the photocatalysts to remove co-existent pollutants simultaneously. Herein, we introduced the surficial activity sites into the bismuth oxybromide (BiOBr), including the Bi/Bi-O defects and hetero Cu atoms, and then the higher photocatalytic activity and selectivity of BiOBr were realized for degradation phenol and ciprofloxacin (CIP). It can be found that the Bi/Bi-O defects played more important role in enhancing the photocatalytic activity for degradation of phenol, while the Cu atoms significantly improved the photocatalytic activity for removing CIP. Moreover, the heterogeneous Cu atoms as the activity sites excited the reaction between phenol and CIP even under dark condition and were beneficial for synchronously removing phenol and CIP. This work provides a feasible way for BiOX photocatalyst to remove co-existent pollutants and may have a practical application.
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