查找使用阿拉丁产品的科研文献

Cobalt(II)-Catalyzed Selective C2–H Heck Reaction of Native (N–H) Indoles Enabled by Salicylaldehyde Ligand

Jia-Wei Li,Shuai Shi,Xiao-Hong Chen,Mao-Gui Huang,Yong-Liang Ban,Hui Zhang,Yue-Jin Liu

Direct functionalization of native (N–H) indoles via C–H activation remains a challenge. Herein, we report a salicylaldehyde-promoted cobalt-catalyzed selective C2–H Heck reaction of native (N–H) indoles with both active and unactivated olefins in the presence of free N–H bonds. A series of structurally diverse C2-alkenylated native (N–H) indoles including natural product and drug derivatives were prepared directly and effectively without additional preprotection and deprotection procedures.

·H effectively enhance electrocatalytic nitrogen fixation

Yuyao Sun,Yaodong Yu,Wenxia Xu,Di Wu,Yingying Wei,Jianping Lai,Lei Wang

Nowadays, most reported ammonia (NH 3 ) yields and Faradaic efficiency (FE) of electrocatalysts are very low in the field of electrocatalytic nitrogen reduction reactions (NRR). Here, we are reported ·H for the first time in the field of electrocatalytic NRR, which are generated by sulfite (SO 3 2− ) and H 2 O in electrolyte solutions upon exposure to UV light. The high NH 3 yields can achieve 100.7 μg h −1 mg cat −1 , while stability can achieve 64 h and the FE can achieve 27.1% at −0.3 V ( vs . RHE) with UV irradiation. In situ Fourier transform infrared spectroscopy (FTIR), electron spin resonance (ESR), density functional theory (DFT) and 1 H nuclear magnetic resonance (NMR) tests showed that the ∙H effectively lowered the reaction energy barrier at each step of the NRR process and inhibits the occurrence of competitive hydrogen evolution reaction (HER). This explores the path and provides ideas for the field of electrocatalysis involving water.

Atroposelective remote meta-C–H activation

Jian-Jun Li,Jia-Hui Zhao,Hua-Chen Shen,Kevin Wu,Xin Kuang,Peng Wang,Jin-Quan Yu

High pressure, a protocol to identify the weak dihydrogen bonds: experimental evidence of C–H···H–B interaction

Qi Guangyu,Wang Kai,Xiao Guanjun,Zou Bo

Pressure, as a thermodynamic parameter, provides an appropriate method to detect weak intermolecular interactions. The C–H···H–B dihydrogen bond is so weak that the experimental evidence of this interaction is still limited. A combination of in situ high pressure Raman spectra and angle-dispersive X-ray diffraction (ADXRD) experiments was utilized to explore the dihydrogen bonds in dimethylamine borane (DMAB). Both Raman and ADXRD measurements suggested that the crystal structure of DMAB is stable in the pressure region from 1 atm (1 atm=1.01325×10 5 Pa) to 0.54 GPa. The red shift of CH stretching and CH 3 distortion modes gave strong evidence for the existence of C–H···H–B dihydrogen bonds. Further analysis of Raman spectra and Hirshfeld surface confirmed our proposal. This work provided a deeper understanding of dihydrogen bonds. And we wish that high pressure could be applied to identify other unconfirmed hydrogen or dihydrogen bond.

Calendering-mediated TOCNF molecular slippage and h-BN aggregation on compactness and thermal conductivity of h-BN/TOCNF composites

Xian Wu,Xiu Wang,Yiwen Chen,Yifei Qu,Hao Zhang,Tingting Xu,Huiyang Bian,Guigan Fang,Hongqi Dai,Chen Su

Pore structures and interface issues have long impeded significant improvements in the thermal conductivity of biphasic composites. This work introduced a calendering technique, adapted from the traditional papermaking industry, to address these challenges in hexagonal boron nitride/tempo-oxidized cellulose nano-fiber (h-BN/TOCNF) composites. Calendering effectively reduced porosity, enhanced compactness, and improved the interface between the two phases. The results indicated that without calendering, the thermal conductivity of the composites increased with higher h-BN loading. At 50 wt% h-BN content, the through-plane thermal conductivity reached 0.82 W/m·K, which was 116% higher than that of a pure TOCNF film (0.38 W/mK). Contrary to expectations, higher calendering pressure did not yield better performance. The optimal balance was achieved with the composites containing 30 wt% h-BN processed at 2 MPa (h-BN30/TOCNF-2 composites), achieving a high thermal conductivity of 0.71 W/m·K coupled with the highest mechanical strength (40.21 MPa). This synergistic enhancement was attributed to the molecular slippage of TOCNF and preferential orientation of h-BN induced by appropriate calendering pressure, leading to tighter bonding and the formation of a “brick-mortar-brick” structure conductive to phonon transfer and mechanical reinforcement. This work demonstrates that calendering, a simple and scalable post-processing technique, can effectively engineer the microstructure of biphasic composites, leading to simultaneous enhancement in thermal and mechanical properties.

The effect of h-BN content on mechanical properties, microstructure and machinability of hot-pressed h-BN/Si3N4 composites

Song Wu,Yongfeng Xia,Ming Zhu,Jun Zhao,Dongxu Yao,Yu-Ping Zeng

Si 3 N 4 ceramics now face new applications and challenges in the semiconductor field. The preparation of h-BN/Si 3 N 4 machinable ceramics incorporating 5–30 vol% h-BN via hot-pressing was carried out. This study systematically explored how the varying h-BN content influenced the composite's microstructure, mechanical attributes, and machinability . The results showed that some of the h-BN was encapsulated by growing Si 3 N 4 grains to form an intragranular structure during the process of hot-pressing, while the remaining h-BN exhibited uniform distribution along grain boundaries. The Si 3 N 4 phase transition in composites was inhibited by excessive h-BN, accompanied by a higher decrease in densification. The sample containing 20 vol% h-BN exhibited the best comprehensive performance, with high mechanical strength and excellent machinability. The bending strength and fracture toughness remained high at 862 MPa and 10.3 MPa m 1/2 , and could be effortlessly machined with cemented carbide drills. Additionally, the machinability of the composites was systematically characterized through observations of crack propagation paths, fitting of R-curves, and mechanical drilling tests.

Effect of chitosan on the mechanical properties and acid resistance of metakaolin-blast furnance slag–based geopolymers

Wang Tianyu,Yang Lang,Rao Feng,Jiang Kaixi,Byrynnai Choduraa

Adding organics in the process of geopolymer synthesis can combine the functional groups of organics with the three-dimensional structure of geopolymer, thus changing the properties of geopolymer such as compressive strength, flexural strength, and acid resistance. In this work, excellent mechanical properties and acid resistance of metakaolin-blast furnance slag (Mk-BFS)-based geopolymer were synthesized by the incorporation of chitosan. The formation of sodium-alumino-silicate-hydrate (N-A-S–H) gel and calium-alumino-silicate-hydrate (C-A-S–H) gel in geopolymerization were characterized by 29 Si nuclear magnetic resonance (NMR). At 5% of chitosan, the compressive strength of Mk-BFS-based geopolymer could reach to 33.7 MPa. The results could be ascribed to that chitosan reacts with geopolymer to generate new C-O-Si structure meanwhile adhesion produced by the combination of positively charged cations and negatively charged ions makes the structure of geopolymer denser. After 7 days of sulfuric acid immersion, the reduction of compressive strength is less than 3 MPa, demonstrating its great acid resistance. The acid resistance of Mk-BFS-based geopolymer could attribute to that the free amino groups in chitosan preferentially react with acid solution and weakened the erosion of sulfuric acid. This study optimizes the compressive strength and acid resistance of geopolymer by adding appropriate amount of chitosan.

In-situ H+–H− pairs induced one-pot tandem acetalization–hydrogenolysis–hydrolysis of furfural to ethyl levulinate over NiCoP/LaPO4

Xiang Li,Wei Li,Ling Wang,Siqi Xu,Tete Xie,Xiu Xiu Zou,Peng Wang,Peng Huang,Shangxing Chen,Zongde Wang,Wenyuan Han,Aliaksandr Tsyhanau,Qiang Deng

Developing a cost-effective catalyst for the selective tandem conversion of furfural (FFA) to ethyl levulinate (EL) is important for synthesizing biofuels and fine chemicals from biomass. However, traditional catalysts prefer the hydrogenation-dehydration-hydrolysis pathway and are slow due to high activation energy requirement. Herein, a NiCoP/LaPO 4 catalyst was prepared via calcination of layered double hydroxide (LDH) precursor, followed by hydrogen reduction, and phosphating. When applied to the tandem of FFA for EL production, it exhibited a high selectivity of 90.1% at 160 °C under ethanol and water via acetalization–hydrogenolysis–hydrolysis route. Catalytic mechanism investigation indicated that in situ hydrogen spillover from NiCoP nanoparticles to the LaPO 4 support, leading to the formation of H + –H − pairs. These H + –H − pairs not only provide Brønsted acid sites to drive FFA acetalization and 2-ethoxymethyl furan (EMF) hydrolysis but also activate the C–O bonds of the key intermediate 2-diethoxymethyl furan (DEMF) via the S N 2 mechanism, markedly accelerating the hydrogenolysis step. Moreover, the NiCoP/LaPO 4 catalyst shows remarkable catalytic versatility for the synthesis of different alkyl levulinates from a range of alcohols (i.e., methanol, propanol, isopropanol, butanol and benzyl alcohol). This study presents an efficient bifunctional catalysis approach for complex tandem reaction pathways aimed at synthesizing alkyl levulinate by hydrogen spillover to generate transient H + –H − pairs.

Pd/TiC/Ti electrode with enhanced atomic H* generation, atomic H* adsorption and 2,4-DCBA adsorption for facilitating electrocatalytic hydrodechlorination

Zimo Lou,Zheni Wang,Jiasheng Zhou,Chuchen Zhou,Jiang Xu,Xinhua Xu

Electrocatalytic hydrodechlorination (ECH) has been proposed as a potential technology for the effective degradation of organochlorine contaminants. In this study, a nanoscale Pd/TiC catalyst with low resistance was dip-coated onto Ti, aiming to fabricate a stable Pd/TiC/Ti electrode with enhanced ECH reactivity for efficient dechlorination. Electrochemical techniques indicated that the Pd/TiC/Ti electrode had a larger electrochemically active surface area and more rapid interfacial charge transfer than the conventional Pd/C/Ti electrode. In a batch experiment, the dechlorination rate for ECH of 2,4-dichlorobenzoic acid (2,4-DCBA, a model pollutant) by Pd/TiC/Ti was 1.3–14.5 times higher than those by Pd/C/Ti, Pd/MWCNTs/Ti, and Pd/MoS2/Ti, respectively. Scavenger experiments, ESR spin-trapping spectroscopy, and cyclic voltammetry clarified the intensified atomic H* generation by Pd/TiC/Ti. DFT calculations revealed that Pd/TiC/Ti had stronger binding ability with atomic H* (Eads: −2.89 eV vs. −2.44 eV) and 2,4-DCBA (Eads: −3.62 eV vs. −2.15 eV), respectively, when compared with Pd/C/Ti. As a result, enhanced generation of atomic H*, together with strengthened adsorption of atomic H* and 2,4-DCBA, would contribute to a faster ECH reaction. The Pd/TiC/Ti electrode retained its reactivity after 10 successive batch experiments (80 h), and showed high tolerance to the constituents in actual water matrices including lake water and river water. This study proposed a promising ECH electrode for the treatment of chlorinated organics in water matrices.

The Pt/h-BN/BiOBr composite towards photocatalytic degradation of bisphenol A: the synergistic effect of h-BN and Pt

He Bing,He Wenhui,Wang Yawen

Semiconductor photocatalyst as a new type of green and sustainable energy material has extensively used in wastewater and gas treatment. In this work, we prepared Pt/h-BN/BiOBr composite by an alcohol-soluble hydrolysis-assisted photoreduction method. The photocatalytic activity was evaluated by the degradation of bisphenol A under simulated sunlight, and the degradation efficiency of BiOBr, h-BN/BiOBr, Pt/BiOBr, and Pt/h-BN/BiOBr were 55.13%, 74.91%, 89.00%, and 98.54%, respectively. The results showed single composited with h-BN or Pt could improve the photocatalytic performance of BiOBr, while double composited with h-BN and Pt could play a synergistic effect on further improving the activity. The interaction between h-BN and BiOBr was electrostatic interactions, and that Pt as a plasma metal was coupling with BiOBr due to its localized surface plasmon resonance (LSPR) effect. The composition, morphology, optical property, and separation efficiency of photo-induced carriers and dominant active radicals were investigated. Based on the results, a possible mechanism was proposed. The excellent photocatalytic activity of Pt/h-BN/BiOBr composite photocatalyst could be attributed to the broadened light-response range after Pt loading, and enhanced electron–hole separation efficiency due to the electron capturer role of Pt and the hole transfer function of h-BN.

Re-examining the suitability of high magnesium nickel slag as precursors for alkali-activated materials

Tao Yang,Zuhua Zhang,Huajun Zhu,Xuan Gao,Chendong Dai,Qisheng Wu

High-magnesium nickel slag (HMNS) has shown the potential as precursor in the production of alkali-activated materials (AAMs). This study re-examines the suitability of HMNS by comparatively investigating the reactivity of four different sourced HMNSs and analyzing impacts of the magnesium sources in HMNS on the reaction products of AAMs. Results show that the cooling way plays a determinant role of their mineral compositions. The air-cooled HMNSs contain only ∼30 wt% glassy phases, while the water-quenched one is dominantly amorphous. The reactivity of HMNS determined by the dissolution tests correlates well with the calculated depolymerization degree of glasses. HMNS indeed exhibits lower reactivity than the precursors commonly used for AAMs production, such as fly ash and blast furnace slag . In the HMNS samples in the sodium hydroxide solution, M-S-H, C-S-H and hydrotalcite are the main reaction products. The OH − ions in the aqueous system react with Mg 2+ to form the brucite, indicating that there is still a volume expansion risk if sodium hydroxide is used as activator. In comparison, only M-S-H and C-S-H gels are coexistent in the samples leached in the sodium silicate solution, because of the kinetic hindrance of soluble silicates for the formation of hydrotalcite and brucite.

SLC7A11 is an unconventional H+ transporter in lysosomes

Nan Zhou,Jingzhi Chen,Meiqin Hu,Na Wen,Weijie Cai,Ping Li,Liding Zhao,Yaping Meng,Dongdong Zhao,Xiaotong Yang,Siyu Liu,Fangqian Huang,Cheng Zhao,Xinghua Feng,Zikai Jiang,Enjun Xie,Hongxu Pan,Zhidong Cen,Xinhui Chen,Wei Luo,Beisha Tang,Junxia Min,Fudi Wang,Junsheng Yang,Haoxing Xu

Lysosomes maintain an acidic pH of 4.5–5.0, optimal for macromolecular degradation. Whereas proton influx is produced by a V-type H + ATPase, proton efflux is mediated by a fast H + leak through TMEM175 channels, as well as an unidentified slow pathway. A candidate screen on an orphan lysosome membrane protein (OLMP) library enabled us to discover that SLC7A11, the protein target of the ferroptosis-inducing compound erastin, mediates a slow lysosomal H + leak through downward flux of cystine and glutamate, two H + equivalents with uniquely large but opposite concentration gradients across lysosomal membranes. SLC7A11 deficiency or inhibition caused lysosomal over-acidification, reduced degradation, accumulation of storage materials, and ferroptosis, as well as facilitated α-synuclein aggregation in neurons. Correction of abnormal lysosomal acidity restored lysosome homeostasis and prevented ferroptosis. These studies have revealed an unconventional H + transport conduit that is integral to lysosomal flux of protonatable metabolites to regulate lysosome function, ferroptosis, and Parkinson’s disease (PD) pathology.