Latest ArticlesLight-driven nitrogen fixation to produce ammonia is a green and economical technology of nitrogen reduction but is still quite challenging, especially in an air atmosphere without any sacrificial reagents. Herein, we demonstrate efficient photocatalytic nitrogen fixation using water and air directly by loading lanthanide–transition metal (4f–3d) cluster NdCo3 on two-dimensional P-doped graphitic carbon nitrides (PCN) material surface. Benefiting from the increase in the number of nitrogen vacancies (NVs) and highly matched band gap structure and excellent hole trapping ability of clusters, the NdCo3/PCN photocatalyst exhibits efficient nitrogen reduction activity with 371 (in air) and 825 µmol h−1 g−1 (in pure nitrogen) without any sacrificial reagents. The introduction of potassium sulfate inhibits hydrogen production and promotes nitrogen reduction activation. This work suggests that anchoring precisely structured clusters on 2D materials may enhance photocatalytic nitrogen reduction under normal temperature and pressure.
Modern chromatography is increasingly focused on miniaturization and integration. Compared to conventional liquid chromatography, microfluidic chip liquid chromatography (microchip-LC) has the potential due to its zero-dead volume connection and ease of integration. Nano-sized packings have the potential to significantly enhance separation performance in microchip-LC. However, their application has been hindered by packing difficulties. This study presents a method for packing nano-sized silica particles into a microchannel as the stationary phase. The microchip-LC packed column was prepared by combining the weir and the porous silica single-particle as frit to retain the packing particles. A surface tension-based single-particle picking technique was established to insert porous single-particle frit into glass microchannels. Additionally, we developed a slurry packing method that utilizes air pressure to inject nano-sized packing into the microchannel. Pressure-driven chromatographic separation was performed using this nano-packed column integrated into a glass microchip. The mixture of four PAHs was successfully separated within just 8 min using a 5 mm separation channel length, achieving high theoretical plates (106 plates/m). Overall, these findings demonstrate the potential of utilizing nano-sized packings for enhancing chromatographic performance in microchip systems.
Mg-doped manganese oxide octahedral molecular sieve (Mg-OMS-2) catalysts were prepared by hydrothermal method. The photothermal degradation performance of these catalysts for formaldehyde (HCHO) in batch system and continuous system was investigated. The light absorption of OMS-2 was increased by Mg-doped, especially for near infrared light, which promoted surface temperature reach a maximum of 214.8 ℃ under xenon irradiation. At this temperature, the reinforced surface lattice oxygen and oxygen vacancy that formed by lattice distortion via Mg-doped were activated. The best HCHO elimination efficiency was achieved over Mg0.2/OMS-2 catalyst with Mg2+/Mn2+ = 1/5, which could reduce HCHO from 250 ppm to 10 ppm within 20 min. The in situ DRIFTS was also carried out to monitor the changes in the content of reaction intermediates and analyze the degradation paths of HCHO. It was found the HCHO was attacked by formed •OH and •O2− to generate formate species and carbonate species, and finally transformed to CO2 and H2O. This photothermal catalytic oxidation process exhibited a high efficiency purification of HCHO without the help of extra energy consumption.
Humans have relied on biomass for survival and development since the Stone Age. All aspects of human needs for materials are covered by tools, fuel, and buildings. Nowadays, metals and petroleum-based materials are widely used in highly developed industries. Unfortunately, environmental contamination and the loss of natural resources have led to the reemergence of biomass resources as efficient and sustainable energy sources. Notably, simple and direct applications can no longer meet the demand for functionalization, high performance of materials and construction materials. Therefore, it is imperative to modify biomass and combine its utilisation to produce functionalization and high performance materials. For example, construction materials with superior mechanical properties and water resistance can be produced by reinforcing fibres to facilitate crosslinking. Water-oil separation or adsorption effects of hydrogels and aerogels are determined by the porosity and lightness of biomass, biocomposite conductor is prepared by chimaeric conductive material. Here, we review the approaches that have been taken to devise an environmentally friendly yet fully recyclable and sustainable functionalised biocomposites from biomass and its potential directions for future research.
Due to the high electrophilic nature of azo-dienophiles, azo-Diels–Alder proceeds rapidly even without the need of a catalyst and is therefore regarded as the "click reaction". This spontaneity causes strong background reaction and poses a daunting challenge to chemists for developing the catalytic asymmetric version. Reported herein is the first catalytic asymmetric dearomative azo-Diels–Alder reaction between 2-vinylindoles and triazoledione. This protocol makes use of the high energy barrier of dearomatization to avert the strong background reaction of azo-Diels–Alder reaction, allowing the implementation of the projected reaction at ambient temperature. Density functional theory calculations have been performed to gain insights into the reaction mechanism and the origins of the enantioselectivity. By using this method, a variety of tetracyclic indole derivatives have been readily prepared in good to excellent yields and with excellent diastereo- and enantio-selectivities (33 examples, up to 97% yield and > 99% ee, > 20:1 dr).
Inverse vulcanized polymers (IVPs) that generated from elemental sulfur and smaller amounts of alkenes have found broad promising applications such as cathode materials for Li-S batteries, dynamic and repairable materials, optics applications, and metal sorption. However, their exploration in organic synthesis is still unprecedented. Here we first report the application of inverse vulcanized polymers in catalysis for organic transformations. A biomass-derived inverse vulcanized polymer (IVP-EAE) is found to be capable of catalyzing cross-coupling reactions in a transition-metal-free fashion under visible light. This method allows the direct CH functionalization of pyrroles and N-arylacrylamides with (hetero)aryl halides, respectively, leading to the formation of two sets of structurally important scaffolds including pyrrole-containing biaryls and 3,3′-disubstituted oxindoles with high selectivity. We anticipate this study will not only unveil the new potential of IVPs, but also offer a distinct type of catalysts for organic transformations.
The research on gas-liquid multiphase reactions using micro reactors is becoming increasingly widespread, given their excellent mass transfer performance. Establishing an accurate and reliable method to measure the gas-liquid mass transfer performance of micro reactors is crucial for evaluating and optimizing the design of micro reactor structure. In this paper, the physical absorption method of aqueous solution-CO2 and the chemical absorption method of sodium carbonate solution-CO2 were proposed. By analyzing the chemical reaction equilibrium during the absorption process, the relationship between the mass transfer of CO2 and the solubility of hydroxide ions in the solution was established, and the total gas-liquid mass transfer coefficient was immediately obtained by measuring the pH value. The corresponding testing platform and process have been established based on the characteristics of the proposed method to ensure fast and accurate measurement. In addition, the chemical absorption method takes into account temperature factors that were not previously considered. The volumetric mass transfer coefficient measured by these two methods is in the same range as those measured by other methods using the same microchannel structure in previous literature. The methods have the advantages of low equipment cost, faster measurement speed, and simpler procedures, which can facilitate its wide application to the evaluation of the mass transfer performance and hence can guide the structure optimization of microchannel reactors.
Doyle-Kirmse rearrangement reactions have received continuous attention as an important method for constructing complex chemical structures. Herein, we disclosed an efficient rhodium-catalyzed Doyle-Kirmse rearrangement reaction, which can simultaneously construct CC bonds and CX (X = S/Se) bonds using sulfoxonium ylides as starting materials to obtain sulfur- or selenium-containing compounds. This strategy is characterized by the safer and greener carbene precursor, high yields and broad substrate scope, possessing a wide range of application.
A facile TfOH-catalyzed oxidative cyclization of allyl compounds and isocyanide has been developed with the assistance of DDQ, where isocyanide is used as the crucial "N" and "CN" sources. Highly functionalized 2-cyanopyrroles are constructed efficiently through a new formal [3 + 2] mode, demonstrating diverse reactivity and synthetic utility in organic chemistry. 2-Cyanopyrrole is converted into a nucleobase analogue of Remdesivir and 5H-pyrrolo[2, 1-a]isoindole through a three-step or a two-step sequence, respectively. This protocol features broad substrate scope, operational simplicity and good functional group tolerance.
A novel N, O modified Mn3O4@porous carbon catalyst (NOC-Mn3O4) was prepared by direct carbonization using the manganese-metal organic framework (Mn-MOF) and covalent organic framework (COF) as precursors to activate peroxymonosulfate (PMS) for the degradation of bisphenol A (BPA) and rhodamine B (RhB). Benefiting from the N and O co-doping of COF, larger specific surface area, faster electron transfer and Mn cycling, the optimum 1NOC-Mn3O4 could significantly improve the degradation performance of BPA and RhB (92.1% and 96.9% within 30 min) as compared to C-Mn3O4 without COF doping. In addition, 1NOC-Mn3O4 showed good reusability and strong anti-interference ability. Radical quenching experiments, X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance spectrometer (EPR) and electrochemical tests showed that the 1NOC-Mn3O4/PMS system degraded BPA and RhB by both radical and non-radical pathways. Moreover, the possible degradation pathways of BPA and RhB were proposed by liquid chromatography-mass spectrometry (LC-MS). Except for that, the toxicity of BPA, RhB and their intermediates were evaluated. This study opens up a new prospect for the design of COF-doped PMS catalysts.
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