Latest ArticlesDensity functional theory calculations have been performed to investigate the dipeptide phosphine-catalyzed hydroamination of enones with pyridazinones. The computations reveal that a number of the NH···O hydrogen-bonding interactions with the pyridazinone moiety and the C-H···O hydrogen-bonding interactions with the enone moiety are present in the enantioselectivity-determining Michael addition transition states. The experimentally-observed catalyst-controlled enantiodivergence is mainly attributed to the significant impact of the substituent of the amide moiety of the dipeptide phosphine on the relative strength of the NH···O hydrogen-bonding interactions, which was found to affect the Si face attack transition state, enabling the enantioselectivity switch upon change of chiral dipeptide phosphine catalyst.
Supramolecular assemblies constructed through the encapsulation of conductive polymers (CPs) by macrocyclic molecules have attracted increasing interest in the fields of supramolecular chemistry and electrochemistry. In this work, an effective strategy was reported to improve the stability and conductivity of CPs by electrochemically constructing different supramolecular assemblies composed of macrocycles and CPs. Typically, we uploaded zinc-based MOF (ZIF-8) onto carbon nanotube film (CNTF) and further electrically deposited macrocycles and CPs to gain the flexible conductive electrodes. Herein, five different supramolecular macrocycles, including α-cyclodextrin (α-CD), sulfato-β-cyclodextrin (SCD), sulfonatocalix[4]arene (SC[4]), cucurbit[6]uril (CB[6]) and cucurbit[7]uril (CB[7]) were utilized and the electrochemical performances of the assembly electrodes increased in an order of α-CD < SCD < SC[4] < CB[6] < CB[7], significantly improving the areal capacitance up to 1533 mF/cm2. This strategy may provide a new way for the application of macrocyclic supramolecules in electrochemical systems.
Silver-catalyzed decarboxylative C-H alkylation of cyclic aldimines with abundant aliphatic carboxylic acids has been realized under mild reaction conditions generating the corresponding products in moderate to good yields (32%-91%). In addition, a gram-scale reaction, late-stage modification of drug, synthetic transformation of the product, and further application of the catalytic strategy were also performed. Preliminary studies indicate that the reaction undergoes a radical process.
To achieve an efficient photocatalytic for clean energy production and environmental remediation, the highly active Fe-doped and terephthalaldehyde-modified carbon nitride (Fe-CN/NTE) isotypic heterojunction photocatalyst is constructed via a simple annealing method for degradation of organic pollutants with simultaneous resource recovery. The Fe-CN/NTE catalyst exhibits a 93% removal rate of p-nitrophenol (4-NP) and a 1.72 mmol/g H2 evolution rate in 2 h simultaneously under visible light irradiation, which are higher than those of pristine CN, Fe-CN, and NTE, respectively. Photoelectrochemical tests show that the excellent photocatalytic performance of Fe-CN/NTE comes from the improved migration, transportation, and separation of photoinduced charge carriers and expanded light-harvesting range. Moreover, hydroxyl radical (OH), electron (e−), and hole (h+) are the main active species and the rational mechanism of 4-NP photodegradation was proposed based on scavenger measurements and liquid chromatography-mass spectrometry (LC-MS), respectively. Isotypic heterojunction Fe-CN/NTE photocatalyst possesses excellent stability in the H2 evolution and 4-NP degradation during five-run cycle tests, posing as a promising candidate in practical works for organic pollution and energy challenges.
A novel carbon-rich g-C3N4 nanosheets with large surface area was prepared by facile thermal polymerization method using urea and 1, 3, 5-cyclohexanetriol. Plenty of carbon-rich functional groups were introduced into the surface layers of g-C3N4, which constructed the built-in electric field (BIEF) and resulted in improved charge separation; therefore, the carbon-rich g-C3N4 displayed superior photocatalytic activity for amoxicillin degradation under solar light. The contaminant degradation mechanism was proposed based on radical quenching experiments, intermediates analysis and density functional theory (DFT) calculation. Moreover, the reusing experiments showed the high stability of the material, and the amoxicillin degradation under various water matrix parameters indicated its high applicability on pollutants treatment, all of which demonstrated its high engineering application potentials.
A self-synthesized bi-pyridine chelating resin (PAPY) could separate Cu(Ⅱ)/Ni(Ⅱ)/Fe(Ⅱ) sequentially from strong-acidic pickling wastewater by a two-stage pH-adjusted process, in which Cu(Ⅱ), Ni(Ⅱ), and Fe(Ⅱ) were successively preferred by PAPY. In the first stage (pH 1.0), the separation factor of Cu(Ⅱ) over Ni(Ⅱ) reached 61.43 in Cu(Ⅱ)-Ni(Ⅱ)-Fe(Ⅱ) systems. In the second stage (pH 2.0), the separation factor of Ni(Ⅱ) over Fe(Ⅱ) reached 92.82 in Ni(Ⅱ)-Fe(Ⅱ) systems. Emphasis was placed on the selective separation of Cu(Ⅱ) and Ni(Ⅱ) in the first-stage. The adsorption amounts of Cu(Ⅱ) onto PAPY were 1.2 mmol/g in the first stage, while those of Ni(Ⅱ) and Fe(Ⅱ) were lower than 0.3 mmol/g. Cu(Ⅱ) adsorption was hardly affected by Ni(Ⅱ) with the presence of dense Fe(Ⅱ), but Cu(Ⅱ) inhibited Ni(Ⅱ) adsorption strongly. Part of preloaded Ni(Ⅱ) could be replaced by Cu(Ⅱ) based on the replacement effect. Compared with the absence of Fe(Ⅱ), dense Fe(Ⅱ) could obviously enhance the separation of Cu(Ⅱ)-Ni(Ⅱ). More than 95.0% of Cu(Ⅱ) could be removed in the former 240 BV (BV for bed volume of the adsorbent) in the fixed-bed adsorption column process with the flow rate of 2.5 BV/h. As proved by X-ray photoelectron spectrometry (XPS) and density functional theory (DFT) analyses, Cu(Ⅱ) exerted a much stronger deprotonation and chelation ability toward PAPY than Ni(Ⅱ) and Fe(Ⅱ). Thus, the work shows a great potential in the separation and purification of heavy metal resources from strong-acidic pickling wastewaters.
The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment. In this study, amorphous molybdenum sulfide composites (EDTA-MoSx (x=2, 3)) were fabricated via a facile hydrothermal method mediated by EDTA, which was applied to heavy metal ions (Cu2+, Cd2+, Pb2+, Zn2+ and Ni2+) removal from aqueous solutions. A case study for Cu2+ ions showed that the adsorption capacity of EDTA-MoSx (x=2, 3) was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L. Adsorption mechanisms of different sulfide groups and －COOH of EDTA-MoSx (x=2, 3) were verified systematically via a series of experiments, characterizations, and density functional theory (DFT) calculations. Both bridging S22− and －COOH covalently bonded with Cu2+ ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx (x=2, 3). This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.
In the field of volatile organic compounds (VOCs) pollution control, adsorption is one of the major control methods, and effective adsorbents are desired in this technology. In this work, the density functional theory (DFT) calculations are employed to investigate the adsorption of typical VOCs molecules on the two-dimensional material borophenes. The results demonstrate that both structure of χ3 and β12 borophene can chemically adsorb ethylene and formaldehyde with forming chemical bonds and releasing large energy. However, other VOCs, including ethane, methanol, formic acid, methyl chloride, benzene and toluene, are physically adsorbed with weak interaction. The analysis of density of states (DOS) reveals that the chemical adsorption changes the conductivity of borophenes, while the physical adsorption has no distinct effect on the conductivity. Therefore, both χ3 and β12 borophene are appropriate adsorbents for selective adsorption of ethylene and formaldehyde, and they also have potential in gas sensor applications due to the obvious conductivity change during the adsorption.
As an important component of the atmosphere, ammonia (NH3) plays a very important role in maintaining the balance of environment. However, it is also one of the most toxic gases that can cause damage to the human respiratory system and mucous membranes even at low concentrations. As such, development of highly sensitive and selective NH3 sensors is of high significance for environmental monitoring and health maintenance. Herein, we have synthesized Au@Ag@AgCl core-shell nanoparticles (NPs) by oxidative etching and precipitating Au@Ag core-shell NPs using FeCl3 and further used them as optical probes for the colorimetric detection of NH3. The sensing mechanism is based on the fact that the etching of NH3 on AgCl and Ag shell leads to the variations of ingredients and core-to-shell ratio of the Au@Ag@AgCl NPs, thereby inducing noticeable spectral and color changes. By replacing the outmost layer of Ag with AgCl, not only is the stability of the sensor against oxygen significantly enhanced, but also is the sensitivity of the method improved. The method exhibits good linear relationship for the detection of NH3 from 0 to 5000 μmol/L with the limit of detection of 6.4 μmol/L. This method was successfully applied to the detection of simulated air polluted by NH3, indicating its practical applicability for environmental monitoring. This method shows great potential for on-site NH3 detection particularly in remote area, where a simple, fast, low-cost, and easy-to-handle method is highly desirable.
As organic pollutants of emerging concern, organophosphate esters (OPEs) have shown toxicity to organisms after entering the water environment. However, research on OPEs in freshwater in Southwest China is very limited. The levels, distribution and partitioning behavior of OPEs in the Minjiang River and their influencing factors is still unknown. In this study, six OPEs, tri-n-butyl phosphate (TnBP), tri(2-chloroethyl)-phosphate (TCEP), trichloropropyl phosphate (TCPP), triphenyl phosphate (TPhP), tributoxyethyl phosphate (TBEP), and tris(2-ethylhexyl)-phosphate (TEHP), were determined in surface water, suspended particle matter (SPM) and sediments of the Minjiang River. The results showed that the average concentrations of Σ6OPEs in surface water, SPM and sediments of the Minjiang River were 199.32±124.95 ng/L, 38463.79±45641.89 ng/g dry weight (dw) and 76.45±28.00 ng/g dw, respectively. High concentrations of OPEs were detected in SPM samples, indicating that more attention should be paid to pollution in SPM. It is worth noting that the variation trend of OPEs in SPM was almost opposite to that in water but basically similar to that in sediment. The proportions of alkyl OPEs in Σ6OPEs increased from surface water to SPM and sediments. Alkyl OPEs were the main pollutants in SPM (10.44%–80.88% of Σ6OPEs, mean of 54.52%) and sediments (59.08%–81.30% of Σ6OPEs, mean of 68.91%), whereas chlorinated OPEs were the most abundant components in surface water (43.16%–75.99% of Σ6OPEs, mean of 55.50%). The water-sediment partition coefficient (logKOC) of OPEs was 4.97–7.58, while the water-SPM partition coefficient was 6.71–10.00. No significant correlations were found between logKOW and logKOC. KOW was not the main factor affecting the distribution of OPEs in the Minjiang River, China.
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