Latest ArticlesThe addition of cold flow improvers (CFIs) is considered as the optimum strategy to improve the cold flow properties (CFPs) of diesel fuels, but this strategy is always limited by the required large dosage. To obtain low-dosage and high-efficiency CFIs for diesel, 1,2,3,6-tetrahydrophthalic anhydride (THPA) was introduced as a third and polar monomer to enhance the depressive effects of alkyl methacrylate-trans anethole copolymers (C14MC-TA). The terpolymers of alkyl methacrylate-trans anethole-1,2,3,6-tetrahydrophthalic anhydride (C14MC-TA-THPA) were synthesized and compared with the binary copolymers of C14MC-TA and alkyl methacrylate-1,2,3,6-tetrahydrophthalic anhydride (C14MC-THPA). Results showed that C14MC -THPA achieved the best depressive effects on the cold filter plugging point (CFPP) and solid point (SP) by 11 ℃ and 16 ℃ at a dosage of 1250 mg/L and monomer ratio of 6:1, while 1500 mg/L C14MC-TA (1:1) reached the optimal depressive effects on the CFPP and SP by 12 ℃ and 18 ℃. THPA introduction significantly improved the depressive effects of C14MC-TA. Lower dosages of C14MC-TA-THPA in diesel exerted better improvement effects on the CFPP and SP than that of C14MC-TA and C14MC-THPA. When the monomer ratio and dosage were 6:0.6:0.4 and 1000 mg/L, the improvement effect of C14MC-TA-THPA on diesel reached the optimum level, and the CFPP and SP were reduced by 13 ℃ and 19 ℃, respectively. A 3D nonlinear surface diagram fitted by a mathematical model was also used for the first time to better understand the relationships of monomer ratios, dosages, and depressive effects of CFIs in diesel. Surface analysis results showed that C14MC-TA-THPA achieved the optimum depressive effects at a monomer ratio of 6:0.66:0.34 and dosage of 1000 mg/L, and the CFPP and SP decreased by 14 ℃ and 19 ℃, respectively. The predicted results were consistent with the actual ones. Additionally, the improvement mechanism of these copolymers in diesel was also explored.
Simultaneous degradation and detoxification during pharmaceutical and personal care product removal are important for water treatment. In this study, sodium niobate nanocubes decorated with graphitic carbon nitride (NbNC/g-C3N4) were fabricated to achieve the efficient photocatalytic degradation and detoxification of ciprofloxacin (CIP) under simulated solar light. NaNbO3 nanocubes were in-situ transformed from Na2Nb2O6·H2O via thermal dehydration at the interface of g-C3N4. The optimized NbNC/g-C3N4–1 was a type-Ⅰ heterojunction, which showed a high conduction band (CB) level of −1.68 eV, leading to the efficient transfer of photogenerated electrons to O2 to produce primary reactive species, •O2−. Density functional theory (DFT) calculations of the density of states indicated that C 2p and Nb 3d contributed to the CB, and 0.37 e– transferred from NaNbO3 to g-C3N4 in NbNC/g-C3N4 based on the Mulliken population analysis of the built-in electric field intensity. NbNC/g-C3N4–1 had 3.3- and 2.3-fold of CIP degradation rate constants (k1 = 0.173 min−1) compared with those of pristine g-C3N4 and NaNbO3, respectively. In addition, N24, N19, and C5 in CIP with a high Fukui index were reactive sites for electrophilic attack by •O2−, resulting in the defluorination and ring-opening of the piperazine moiety of the dominant degradation pathways. Intermediate/product identification, integrated with computational toxicity evaluation, further indicated a substantial detoxification effect during CIP degradation in the photocatalysis system.
Rational tuning of crystallographic surface and metal doping were effective to enhance the catalytic performance of metal organic frameworks, but limited work has been explored for achieving modulation of crystal facets and metal doping in a single system. MIL-68(In) was promising for photocatalytic applications due to its low toxicity and excellent photoresponsivity. However, its catalytic activity was constrained by severe carrier recombination and a lack of active sites. Herein, increased (001) facet ratio and active sites exposure were simultaneously realized by cobalt doping in MIL-68(In) through a one-pot solvothermal strategy. Optimized MIL-68(In/Co)-2.5 exhibited remarkable catalytic performance in comparison with pristine MIL-68(In) and other MIL-68(In/Co). The reaction kinetic constant and degradation efficiency of MIL-68(In/Co) were approximately twice and 17% higher than the pristine MIL-68(In) in 36 min reaction, respectively. Density functional theory calculations revealed that Co dopant could modulate the orientation of MIL-68(In) facets, facilitate the exchange of electrons and reduce the adsorption energy of peroxymonosulfate (PMS). This work provides a novel pathway for improvement of In-based MOFs in PMS/vis system, it also promotes the profound comprehension of the correlation between crystal facet regulation and catalytic activation in the PMS/vis system.
As antibiotic pollutants cannot be incompletely removed by conventional wastewater treatment plants, ultraviolet (UV) based advanced oxidation processes (AOPs) such as UV/persulfate (UV/PS) and UV/chlorine are increasingly concerned for the effective removal of antibiotics from wastewaters. However, the specific mechanisms involving degradation kinetics and transformation mechanisms are not well elucidated. Here we report a detailed examination of SO4•−/Cl•-mediated degradation kinetics, products, and toxicities of sulfathiazole (ST), sarafloxacin (SAR), and lomefloxacin (LOM) in the two processes. Both SO4•−/Cl•-mediated transformation kinetics were found to be dependent on pH (P < 0.05), which was attributed to the disparate reactivities of their individual dissociated forms. Based on competition kinetic experiments and matrix calculations, the cationic forms (H2ST+, H2SAR+, and H2LOM+) were more highly reactive towards SO4•− in most cases, while the neutral forms (e.g., HSAR0 and HLOM0) reacted the fastest with Cl• for the most of the antibiotics tested. Based on the identification of 31 key intermediates using tandem mass spectrometry, these reactions generated different products, of which the majority still retained the core chemical structure of the parent compounds. The corresponding diverse transformation pathways were proposed, involving S−N breaking, hydroxylation, defluorination, and chlorination reactions. Furthermore, the toxicity changes of their reaction solutions as well as the toxicity of each intermediate were evaluated by the vibrio fischeri and ECOSAR model, respectively. Many primary by-products were proven to be more toxic than the parent chemicals, raising the wider issue of extended potency for these compounds with regards to their ecotoxicity. These results have implications for assessing the degradative fate and risk of these chemicals during the AOPs.
Recent advances in drug development and bioactive molecules that covalently target lysine residues have shown substantial progress. Both reversible and irreversible covalent inhibitors are developed for targeting lysine residues. The identification of protein targets and binding sites of these lysine-targeting molecules in the whole proteome is crucial to understand their proteome-wide selectivity. For covalent inhibitors, the pull down-based methods including activity-based protein profiling (ABPP) are commonly used to profile their target proteins. For covalent reversible inhibitors, it is not easy to pull down the potential protein targets as the captured proteins may get off beads because of the reversible manner. Here, we report a pair of isotope-labelled click-free probes to competitively identify the protein targets of lysine-targeting covalent reversible small molecules. This pair of isotopic probes consists of a lysine-reactive warhead, a desthiobiotin moiety and isotopicable linker. This integrated probe could eliminate the background proteins induced by the click chemistry during the pull-down process. To demonstrate the feasibility of our newly-developed probes for the protein target identification, we selected the natural product Gossypol in that we proved for the first time that it could modify the lysine residue in a covalent reversible manner. Finally, we confirmed that this pair of integrated probes can be used in a competitive manner to precisely identify the protein target as well as binding sites of Gossypol. Interestingly, pretreatment of Gossypol could stop the antibody from recognizing Gossypol-binding proteins. Together, our isotope-labeled click-free probes could be used for whole-proteome profiling of lysine-targeting covalent reversible small molecules.
The selective conversion of CO2 and NH3 into valuable nitriles presents significant potential for CO2 utilization. In this study, we exploited the synergistic interplay between silicon and fluoride to augment the nickel-catalyzed reductive cyanation of aryl pseudohalides containing silyl groups, utilizing CO2 and NH3 as the CN source. Our methodology exhibited exceptional compatibility with diverse functional groups, such as alcohols, ketones, ethers, esters, nitriles, olefins, pyridines, and quinolines, among others, as demonstrated by the successful synthesis of 58 different nitriles. Notably, we achieved high yields in the preparation of bifunctionalized molecules, including intermediates for perampanel, derived from o-silylaryl triflates, which are well-known as aryne precursors. Remarkably, no degradation of substrates or formation of aryne intermediates were observed. Mechanistic studies imply that the formation of penta-coordinated silyl isocyanate intermediates is crucial for the key C–C coupling step and the presence of vicinal silyl group in the substrate is beneficial to further make this step kinetically favorable.
The development of general and practical strategies toward the construction of medium-sized rings is still challenging in organic synthesis, especially for the multiple stereocenters control of substituted groups on the ring owing to the long distance between groups. Thus, stereoselective synthesis of multi-substituted ten-membered rings is attractive. Herein, a rapid assembly of various highly substituted ten-membered nitrogen heterocycles between two 1,3-dipoles through a tandem [3 + 3] cycloaddition/aza-Claisen rearrangement of N-vinyl-α,β-unsaturated nitrones and aza-oxyallyl or oxyallyl cations are disclosed. Products containing two or multiple stereocenters could be obtained in up to 96% yield with high regioselectivity and diastereoselectivity. Selective N-O bond cleavages of ten-membered nitrogen heterocycles lead to various novel 5,6,6-perifused benzofurans, bicyclo[4.4.0] or bicyclo[5.3.0] skeletons containing three or multiple continuous stereocenters in good yields and high diastereoselectivity. Biological tests show that the obtained ten-membered N-heterocycles and bicyclo[4.4.0] skeletons inhibited nitric oxide generation in LPS-stimulated RAW264.7 cells and might serve as good anti-inflammatory agents.
Algal copper uptake (i.e., Cu bioavailability) in the euphotic zone plays a vital role in algal photosynthesis and respiration, affecting the primary productivity and the source and sink of atmospheric carbon. Algal Cu uptake is controlled by natural dissolved organic Cu (DOCu) speciation (i.e., complexed with the dissolved organic matter) that conventionally could be tested by model prediction or molecular-level characterizations in the lab, while DOCu uptake are hardly directly assessed. Thus, the new chemistry-biology insight into the mechanisms of the Cu uptake process in algae is urgent. The DOCu speciation transformation (organic DOCu to free Cu(Ⅱ) ions), enzymatic reduction-induced valence change (reduction of free Cu(Ⅱ) to Cu(Ⅰ) ions), and algal Cu uptake at the algae-water interface are imitated. Herein, an intelligent system with DOCu colorimetric sensor is developed for real-time monitoring of newly generated Cu(Ⅰ) ions. Deep learning with whole sample image-based characterization and powerful feature extraction capabilities facilitates colorimetric measurement. In this context, the Cu bioavailability with 7 kinds of organic ligands (e.g., amino acids, organic acids, carbohydrates) can be predicted by the mimetic intelligent biosensor within 15.0 min, i.e., the DOCu uptake and speciation is successfully predicted and streamlined by the biomimetic approach.
Bridged bicyclic cores have been recognized as valuable bioisosteres of benzene ring, which are of great value in medicinal chemistry. However, the development of fluorinated bicyclic skeletons, which encompass two privileged elements widely acknowledged for fine tuning the working effect of target molecules, are far less common. Herein, we present a general and practical synthesis of gem–difluorobicyclo[2.1.1]hexanes (diF-BCHs) from readily available difluorinated hexa-1,5-dienes through energy transfer photocatalysis. By taking advantage of an efficient Cope rearrangement, the preparation of both constitutional isomers of diF-BCHs is readily achieved under identical conditions. The operational simplicity, mild conditions and wide scope further highlight the potential application of this protocol. Moreover, computational studies indicated a positive effect of fluorine atoms in lowering either the triplet or FMO energies of the hexa-1,5-diene substrates, thus promoting the present photoinduced [2 + 2] cycloaddition.
The heritage preservation is of great intractability to the conservators as each kind of heritage material has unique and diverse requirements on temperature, humidity and air cleanliness. It is promising for metal-organic frameworks (MOFs), the multifunctional environment remediation materials, to be applied in heritage environmental protection. The advantages of MOFs lie in their multifunction like adsorption, photocatalysis, sterilization, as well as the controllable structure and properties that could be flexibly adjusted as demands, helping the heritage against various environmental threats. Thereby, the applications and the corresponding mechanisms of MOFs in cultural heritage preservation were reviewed in this work, including harmful gas adsorption, surface waterproofing, particulate matters (PM) removal, anti-bacterial and humidity control of environment. Finally, the selection principles and precautions of MOFs in heritage preservation were discussed, aiming to provide a forward-looking direction for the selection and application of MOFs.
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