CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Junjie Xu,Wei Sun,Xiang Xiong,Hongbo Zhang,Lingkun Yang
Spacecraft thermal protection materials need to survive long-term exposure to oxygen-containing environments at 2400 °C. In this study, a high-density and low-porosity metal-ceramic-modified composite was prepared at a low temperature (1500 °C) in the presence of W and Cu using combined slurry brushing and reactive melt infiltration methods. An investigation of the composite formation mechanism and the effects of W and Cu indicated that W and ZrB 2 were formed via dissolution-precipitation and the external diffusion of C and B, respectively. The low reaction temperature and the metallic phases significantly improved the mechanical properties, thermophysical properties, and long-term ablation behaviours of C/C–ZrC–ZrB 2 –W–Cu. Compared to traditional C/C–ZrC, the flexural strength and fracture toughness of the composite increased by 71.56 % and 90.05 % to 345.95 MPa and 14.52 MPa m 1/2 , respectively, and the thermal conductivity increased by 174.93 % to 59.11 W/m·K. In addition, W and Cu effectively lowered the surface temperature by nearly 250 °C during 300 s ablation, and the mass and line ablation rates decreased to −0.272 mg/s and −0.247 μm/s, respectively.
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RARE METALS
·
2025
·
IF 11
Dong Yu-Guo,Kong Wen-Jing,Ma Zhuang,Yang Yong,Wang Ping,Sheng Shi-Xiong,Dong Lin,Gu Xiao-Li,Chen Zu-Peng
The oxidation of lignin model compounds to esters via C–C bond cleavage has attracted considerable attention, as esters could be used as important polymer precursors and pharmaceutical intermediates. However, most studies focus on designing homogeneous or noble metal catalysts and conducting the reactions under basic conditions. Here, we report an efficient process for the C–C bond cleavage of lignin model compounds and selectively producing esters over different shaped CeO 2 (i.e., nanospheres (S), nanorods (R), nanoparticles (P), and nanocubes (C)) under base-free conditions. Specifically, the yield of methyl anisate from the aerobic oxidation of 1-(4-methoxyphenyl)ethanol reaches 77.6% over CeO 2 -S in one hour (91% in 9 h), exhibiting higher performance compared to other evaluated CeO 2 catalysts (6.4%–40.2%). Extensive characterizations and experimental investigations reveal that the density of weak base sites and oxygen vacancies on the CeO 2 surface is positively correlated with the yield of methyl esters. Furthermore, the reaction pathway is investigated, which confirms that 1-(4-methoxyphenyl)ethanol first undergoes two reactions (i.e., etherification and dehydrogenation) to produce intermediates of 1-methoxy-4-(1-methoxy-ethyl)-benzene and 1-(4-methoxyphenyl)ethanone, respectively, followed by a series of functional group transformations to generate the targeted methyl anisate ultimately. Graphical abstract
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Molecular Catalysis
·
2025
·
IF 4.9
Wei Wang,Rui Zhang,Jiaqing Li,Huai Liu,Wenlong Jia,Junhua Zhang,Dan Li,Lincai Peng
Furans are important scaffolds with applications in pharmaceuticals, polymers synthesis and biofuels. The direct production of new types of furans from glucose is therefore significant but remains a great challenge. Herein, we report a facile strategy to produce acetylfurans directly from glucose over MoCs-SiO 2 , with an increase in yield from 35.8 % to 81.4 % compared with pristine Mo-SiO 2 due to the facilitated C−C bond cleavage of glucose. The incorporation of Cs improved the dispersion of Mo species, induced the formation of partially reduced Mo, increased the Lewis acidity and glucose adsorption of the catalyst, and thus shifting the reaction selectivity from C−C coupling to cleavage. Kinetic studies further demonstrated the positive contribution of Cs as a promoter in lowering the activation energy of C−C bond cleavage. This study provides a promising strategy to broaden the range of furanic compounds derived from glucose for product-oriented biorefineries.
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CERAMICS INTERNATIONAL
·
2025
·
IF 5.6
Zhilun Zhang,Wei Xie,Xuanru Ren,Bingqing Zhao,Ziqi Zhao,Qian Wang,Mingliang Li,Hailong Wang
To enhance oxidation resistance of carbon/carbon (C/C) composite materials at 1973 K in static air, a novel bilayer Yb 2 O 3 -HfB 2 -SiC/SiC (denoted YHSS) coatings were engineered via a two-step process combining pack cementation and slurry method. A substantial loading of ceramic phases (∼60 wt %) was incorporated into the SiC ceramic layer to improve thermal stability of the oxide scale at 1973 K. Following pre-oxidation, the YHSS coatings impart effective oxidation protection to C/C composite materials for over 228 h at 1973 K. Coupled experimental and theoretical analyses confirm that Yb and Hf atoms diffuse into the thermally grown SiO 2 layer, thereby reinforcing the SiO 2 network structure. Furthermore, the coating's exceptional performance is attributed to its dense, flaw-free surface morphology and the homogeneous dispersion of high-content ceramic phases throughout the SiC layer, collectively suppressing oxygen permeation.
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NANOTECHNOLOGY
·
2024
·Vol. 35
·期 49
·495704
·
IF 2.9
Gang Xiao,Zishuai Wang,Yu Jin,Fengping Wang
The selective cleavage of lignin C–C bonds is a highly sought-after process with the goal of obtaining low-molecular-weight aromatic chemicals from renewable resources. However, it remains a challenging task to achieve under mild conditions. Photocatalysis is a potentially promising approach to address this issue, but the development of efficient photocatalysts is still in progress. In this study, we introduce the heterostructured TiO2@g-C3N4 photocatalyst for the development of a visible light photocatalytic procedure for the selective cleavage of lignin C–C bonds under mild conditions. The photocatalyst displays favourable visible light absorption, efficient charge separation efficiency, and promising reusability. A typical β–O–4 dimer model, 2-phenoxy-1-phenylethanol, was effectively (96.0% conversion) and selectively (95.0 selectivity) cleaved under visible light at ambient conditions. This photocatalytic procedure was also effective when subjected to solar irradiation or other lignin dimer models with β–O–4 or β-1 linkages. This reaction occurred through a Cβ-centred radical intermediate and a six-membered transition state with photogenerated holes as the primary active species. The Cα–OH oxidative dehydrogenation of the substrate could also take place but was a relatively minor route. This study provides a new photocatalytic procedure for visible-light-driven lignin valorisation and sheds light on the design of high-performance nanocomposite photocatalysts for C–C bond cleavage.
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PubMed
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ADVANCED FUNCTIONAL MATERIALS
·
2025
·
IF 19
Sihang Hu,Haiquan Liu,Mingyu Yang,Huan Dai,Chongyang Tang,Dong He,Xiangheng Xiao
The complex reaction interface and the high reaction barrier for C─C coupling hinder the conversion of CO 2 toward high-value C 2+ products. In this work, thiol is employed to modify facet-controlled Cu nanoparticles, systematically elucidating the tripartite interaction between organic modifiers, active sites, and key intermediates. Theoretical calculations, Kelvin Probe Force Microscope (KPFM), and in situ investigations reveal that the thiol-derived spatial potential field facilitates CO 2 activation and the formation of hydrocarbon intermediates ( * COH). More importantly, the results demonstrate that the C 2+ products of the thiol-modified catalyst are strongly dependent on the crystal planes: the potential field preferentially drives suitable adsorbed * COH to asymmetric * CO- * COH coupling on Cu (100)/(111) interface. Consequently, the C 2+ selectivity of the thiol-modified Cu (100)/(111) interface-rich Cu nanoparticle is intrinsically enhanced, exhibiting high selectivity to C 2+ products with a faradaic efficiency (FE) of 85.44%. Remarkably, the structure achieves a C 2 H 4 FE of 73.79% ± 2.69% with a peak partial current density of 345.75 mA cm − 2 (total current: 1.38 A). Beyond establishing a high-efficiency CO 2 to C 2+ conversion protocol, this study provides mechanistic insights into the selective steering of C─C coupling through tailored surface modifications.
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ACS Catalysis
·
2017
·
IF 10.614
Tingting Hou,Nengchao Luo,Hongji Li,Marc Heggen,Jianmin Lu,Yehong Wang,Feng Wang
Selective cleavage of C–C bonds is pursued as a useful chemical transformation method in biomass utilization. Herein, we report a hybrid CuOx/ceria/anatase nanotube catalyst in the selective oxidation of C–C bonds under visible light irradiation. Using the lignin β-1 model as a substrate offers 96% yields of benzaldehydes. Characterization results by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy element (EDX) mapping reveal that CuOx clusters are highly dispersed on the exposed anatase surface as well as on the nanosized ceria domains. In-depth investigations by Raman and ultraviolet visible diffuse reflectance spectra (UV−vis DRS), together with density functional theory (DFT) calculations, further verify that the CuOx clusters present on the ceria domains increase the concentration of surface defects (Ce3+ ions and oxygen vacancies) and accordingly improve the photocatalytic activity (Yang character); the CuOx clusters decorating on anatase suppress the side reaction (oxy-dehydrogenation without C–C bond cleavage) because of an upward shift in the valence band (VB) edge of anatase (Yin character). Mechanism investigation indicates hydrogen abstraction from β-carbon by photogenerated holes is a vital step in the conversion.
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ADVANCED SYNTHESIS & CATALYSIS
·
2017
·Vol. 359
·期 3
·454-466
·
IF 5.646
Xu Cheng,Weijian Li,Ruifang Nie,Xiaojun Ma,Rui Sang,Li Guo,Yong Wu
A micron-scale palladium(II) material has been successfully prepared using Schiff base-modified hexagonal boron nitride as a support and used for the first time as an efficient and recyclable catalyst in organic synthesis. The morphology, composition, metal loading and thermal stability of the catalyst were studied using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), inductively coupled plasma (ICP) and thermogravimetric (TG) analyses. Then, the micron material was tested in various C–C cross-coupling reactions and exhibited excellent catalytic activities in the Suzuki and Heck reactions. Moreover, the catalyst could be easily recovered by simple filtration and reused at least ten times without significant loss of its catalytic activity. In general, this work demonstrates the possibility of using Schiff-base@hexagonal boron nitride as an efficient support for heterogeneous catalysts.
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Molecular Catalysis
·
2022
·
IF 5.089
Shengnan Zhao,Song Song,Yong You,Yingtian Zhang,Wei Luo,Kaijie Han,Tong Ding,Ye Tian,Xingang Li
Heterogeneous photocatalytic C-C coupling is a green and efficient approach to producing valuable chemicals. The strategies for guiding effective photocatalyst design are desired but still limited. Here, we report visible-light-driven highly selective photocatalytic C-C coupling of benzyl alcohol over surfactant-modified Zn 3 In 2 S 6 semiconductors. A complete switch of product selectivity from benzyl aldehyde (91.5 %) to C-C coupling products (96.5 %) is obtained by the modification of Zn 3 In 2 S 6 with stearyl trimethyl ammonium bromide (STAB). This modification assists the formation of sulfur vacancies on Zn 3 In 2 S 6 to enhance charge carrier separation, thereby increasing the photocatalytic activity. The selectivity switch is mainly attributed to increasing conduction band position of Zn 3 In 2 S 6 by surfactant modification which strengthens the reduction ability of photogenerated electrons to induce the reversible reduction of benzyl aldehyde to ketyl radicals, and partially to the poor oxidation ability of the material that inhibits the oxidation of ketyl radicals to benzyl aldehyde. Encouragingly, this universal protocol has been successfully applied to a series of aromatic alcohols and biomass-derived furanic alcohols to selectively produce C-C coupling products.
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JOURNAL OF MOLECULAR STRUCTURE
·
2023
·
IF 3.8
Peng Xiong,Tong-Wei Zhang,Shi-Ming Li,Mei-Yu Xu,Guang-Ming -Liang,Liu-Cheng Gui,Xiu-Jian Wang
Two tetranuclear copper cages with tubular type, [Cu 4 (BMBA) 4 ((CH 3 ) 2 N) 2 (H 2 O) 2 ] ( 1 ) and [Cu 4 (BMBA) 4 (Bipy)(H 2 O) 2 ] ( 2 ), were successfully constructed by the reaction of Cu(NO 3 ) 2 with dicarboxylic acid 4,4′-[( ethylazanediyl ) bis ( methylene )]-bis[(1,1′-biphenyl)-2-carboxylic acid] (H 2 BMBA) under solvothermal conditions. The complexes 1 and 2 exhibit a similar cage structure, formed by four ligands connecting two binuclear copper paddle-wheel secondary building units (SBUs). Interestingly, the complex 2 was obtained by appropriately binding of 4, 4′-bipyridine (Bipy) molecule on the axial positions of two Cu paddle-wheels inside the cage. For this reason, the complex 2 exhibits excellent stability in some common organic solvents at room temperature and aqueous solutions with a pH of 2 to 12. Upon thermal activation of complex 2 , the coordinated water molecules can be removed, and its exposed metal active-sites show Lewis acid character, which can be used an efficient heterogeneous catalysis of Knoevenagel condensation (C C) and Clauson-Kaas (C N) reactions.
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ANALYTICA CHIMICA ACTA
·
2019
·
IF 5.256
Chao Song,Dan Gao,Shangfu Li,Liping Liu,Xiaowu Chen,Yuyang Jiang
The location of double bond in unsaturated fatty acids (FAs) plays a critical role in their physiological properties. However, structural identification and quantification of unsaturated FAs by mass spectrometry are still challenging. In this work, we reported the coupling of epoxidation reaction of the C=C in unsaturated FAs and liquid chromatography-mass spectrometry (LC-MS) with multiple reaction monitoring (MRM) mode for accurate identification and quantification of C=C isomers of FAs. Epoxidation of the C=C in unsaturated FAs was induced by a dioxide of ketone , tetrahydrothiopyran-4-one 1,1-dioxide, as a catalyst and Oxone as an oxidant in less than 5 min with nearly 100% yield. All the C=C bonds were epoxidized to obtain a single product, simplifying the chromatographic separation of epoxidation products to enable more accurate quantification analysis. The epoxidation products were stable at room temperature and can produce highly abundant diagnostic ions indicative of C=C locations by tandem mass spectrometry using collision-induced association (CID). The application of this approach for the analysis of FAs isomers in human plasma demonstrated the potential of our method for the qualitative and quantitative analysis of unsaturated FAs in complex biological samples, which is valuable in biological and medical analysis.
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JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2018
·Vol. 56
·期 20
·2344-2353
·
IF 2.588
Jiajun Bi,Jian Chen,Yahao Dong,Wen Guo,Dajian Zhu,Tao Li
A new polymer was prepared from 1,3,5-triformylphloroglucinol (noted as TDTB) and o -phenylenediamine through Schiff base condensation reaction, and palladium (II) was immobilized on the polymer (noted as TbPo-Pd(II)). This process was easy to work-up and cost-effective. The structure and composition of TbPo-Pd(II) were fully characterized by FTIR, TGA, XPS, AAS, SEM, and TEM analyses. Meanwhile, this catalyst showed desired thermal stability and excellent performance in water/methanol system for Suzuki and Sonogashira coupling reactions. In addition, this heterogeneous catalyst can be readily recovered by simple filtration with no appreciable Pd leaching in the reaction. This work provides a powerful protocol for rapid access to asymmetrical biphenyls and aryl alkynes. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56 , 2344–2353
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