Molecular Catalysis
·
2019
·
IF 2.938
Zhijie Wang,Anxiang Guan,Mayfair C. Kung,Anyang Peng,Harold H. Kung,Ximeng Lv,Gengfeng Zheng,Linping Qian
Aerobic oxidation of α-C H bond of organic compounds to valuable chemicals is widely investigated in both fundamental research and industry. Due to the good stability of molecular oxygen, severe reaction conditions are generally required. Herein, by in situ synthesis we used molecular oxygen to induce cobalt nanoclusters with the sensitive catalysis in mild selective oxidation. The cobalt containing clusters with an average diameter around 0.9 nm are in situ prepared in the presence of cis -cyclooctene epoxidation and cyclooctene dimer oxide is formed at the interface to stabilize Co clusters with electron donation as an oil-soluble surfactant. The soluble clusters exhibit high activity in selective oxidation of α-C H bond of ethylbenzene into acetophenone and turnover number (TON) reaches about 7 × 10 4 during 50 h’ reaction at 373 K, which is around 960 times more active than the one using CoCl 2 salt as the catalyst, resulting from efficient mass transportation, π bond interaction and oxygen gas activation. Extended work based on this understanding demonstrates that cobalt nanoclusters also effectively catalyze aerobic oxidation of cyclohexene.
研究领域:
化学催化
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有机合成
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
Catalysis Science & Technology
·
2019
·Vol. 9
·期 15
·4002-4009
·
IF 5.726
Tiaohao Zhao,Shanshan Shen,Xiaohui Liu,Yong Guo,Chih-Wen Pao,Jeng-Lung Chen,Yanqin Wang
NbN materials have a wide range of applications in the fields of catalysis and semiconductors, due to their unique chemical and physical properties. However, only a few reports focused on the synthesis of NbN materials with different morphologies due to their harsh nitridation conditions. Herein, we successfully prepared amorphous NbN, spherical NbN (NbN-S) and nanobelt NbN (NbN-B) from different niobium precursors with corresponding morphologies by using urea as a nitrogen source at 750 °C. Comprehensive characterization (including XRD, N2 sorption measurements, ICP-AES, FTIR spectroscopy, TG analysis, SEM, TEM, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS)) revealed the formation of NbN and the structural information of these NbN materials. Based on these characterizations, we found that the amount of surface Nb–OH groups is an important factor for successful nitridation under mild conditions. Moreover, the synthesized NbN materials can be used in the epoxidation of cyclooctene and a very high epoxycyclooctane yield (93.9%) was achieved, which is much higher than that over the corresponding Nb2O5 materials. This excellent catalytic performance of NbN materials is supposedly related to the low-coordinated Nb sites and rich vacancies generated during the special nitridation process.
研究领域:
催化化学
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材料科学
✓ 已验证
DOI
高影响因子
POLYMER
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2024
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IF 4.1
Qingqing Yang,Jinye Wang,Liping Huang,Wei Song,Liang Ding
The properties of synthetic polymers are influenced by the connection mode of polymer chains even polymers made from the same monomer. In this work, the diverse composition systems of cyclooctene-based alternating, random and block azo-copolymers containing imidazolium cation units as side group were successfully achieved based on different metathesis methods in the ionic liquid with good control over the polymerization processes. All these ionic azo-copolymers were tailored to explore the effects of monomers sequences and non-covalent interactions on photoresponsive behaviors and self-assembly morphologies. Since the special alternating structure, UV-light-triggered the shackling trans → cis photoisomerization transition was observed, ultimately spontaneously forming highly regular and uniform polymer vesicle with recoverable size variation in THF directly. Differently, the micellar characterization was carried out by the self-assembly of ionic block azo-copolymers in a selective solvent of toluene to obtain spherical micelle with reversible shape evolution considering nearly 86 % trans→cis relative isomerization efficiency. These interesting results not only demonstrate the diversity of metathesis polymerization but also expand the property of azo-copolymers.
研究领域:
高分子化学
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材料科学
✓ 已验证
DOI
高影响因子
POLYMERS FOR ADVANCED TECHNOLOGIES
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2020
·Vol. 31
·期 11
·2492-2503
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IF 2.578
Fuqiang Zhou,Lucheng Qi,Xuelian He
A series of different molecular weight Polycyclooctene(PCOE) rubber were synthesized via ROMP with G 2 catalyst and Iso-polypropylene (iPP), PCOE and high density polyethylene (HDPE) blends were prepared by micro twin-screw extruder. The effects of PCOE molecular weight and content were investigated by studying the thermal, rheological and mechanical properties of the blends. We observed that the low molecular weight PCOE promoted the dispersion of HDPE, and as the molecular weight and content of PCOE rising, PCOE encapsulated HDPE particles entirely to form a connected core-shell network structure in PP matrix and a certain degree of micro-crosslinked structure which connected the PCOE ‘shell’. Micrographs of the fracture surfaces support the finding that PCOE promoted a finer dispersion and improved the morphological stability of the ternary blends as a compatibillizer. The increasing molecular weight of PCOE enhanced the molecular chains entanglement of the blends resulting in an increase on blends viscosity. The interfacial adhesion of PP/PCOE/HDPE ternary blends improved significantly as PCOE molecular weight increased from 12 kg/mol to 270 kg/mol. The impact strength of the PP/PCOE/HDPE blends increased by 3 times as compared with PP/HDPE blends owing to the addition of 15 wt% HDPE and 15 wt% PCOE( M n = 270 kg/mol).
研究领域:
材料科学
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高分子化学
✓ 已验证
DOI
高影响因子
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
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2025
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IF 2
Yali Zhao,Ziru Wang,Jinxiu Zhai,Xingjian Cao,Peilei He
Graphical The lacunary polyoxometalate ([PW 11 O 39 ] 7− , PW 11 ) can self-assemble with TBAB to form tetrakaidecahedron-like nanodices (NDs). These NDs exhibit significantly higher catalytic activity for the epoxidation of cyclooctene compared to PW 11 alone and nanospheres (NSs) formed from the non-lacunary polyoxometalate ([PW 12 O 40 ] 3− , PW 12 ). DFT studies confirm the critical role of hydroperoxo species generated at the lacunary site in facilitating oxygen transfer to cycloalkenes over PW 11 . The activation of hydrogen peroxide (H 2 O 2 ) as a terminal oxidant holds great promise for catalytic oxidation processes. However, developing an efficient catalyst for the epoxidation of bulky organic molecules with H 2 O 2 , including cyclic alkenes, remains challenging. In this research, a lacunary polyoxometalate (POM)-based tetrakaidecahedron nanodices (NDs) are synthesized by [PW 11 O 39 ] 7− (PW 11 ) clusters with tetrabutylammonium bromide (TBAB). The NDs exhibit significantly enhanced catalytic activity in the epoxidation of cyclooctene, with a yield 55.4 times greater than that of the raw PW 11 . Conversely, nanospheres (NSs) assembled from non-lacunary POM clusters of [PW 12 O 40 ] 3− (PW 12 ) under the same conditions achieve only a 2.9 % yield, highlighting the essential role of the lacunary PW 11 structure in NDs. Raman spectroscopy and density functional theory (DFT) calculations confirm that the active hydroperoxo species from H 2 O 2 activation serves as the effective epoxidizing agent. The reduced energy barrier for H 2 O 2 activation on PW 11 , relative to PW 12 , corroborates the superior activity of the NDs. Furthermore, the intermediate generated post-H 2 O 2 activation shows stronger adsorption of cyclooctene, increasing oxygen transfer to cyclooctene during the epoxidation process. This study demonstrates the exceptional performance of an assembly structure utilizing lacunary POMs for the activation of H 2 O 2 and subsequent oxidation reactions.
研究领域:
催化化学
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材料科学
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理论计算化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
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2017
·Vol. 55
·期 13
·2211-2220
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IF 2.952
Yuchen Feng,Suyun Jie,Bo-Geng Li
Fatty acid-derived cyclooctenes, including n -hexanoic acid ( M1 ), n -octanoic acid ( M2 ), lauric acid ( M3 ), and palmitic acid ( M4 ), were prepared as monomers and polymerized by ring-opening metathesis polymerization (ROMP) using Grubbs second-generation catalyst ( G2 ). In all the cases, the regio-irregular unsaturated polymers with pendent linear branches were obtained, which could be saturated by chemical hydrogenation with TSH/TPA in high conversion, yielding ethylene/vinyl ester copolymers with pendent linear branches on precisely every eighth backbone carbon. Both unsaturated and saturated polymers were amorphous, and their structures were characterized by FTIR, 1 H and 13 C NMR spectra, and elemental analysis. Differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) were used to study their thermal properties. The chain length of branches greatly affected the thermal properties of polymers. After hydrogenation, the thermal degradation stability of polymers was relatively improved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2211–2220
研究领域:
高分子化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
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2012
·Vol. 125
·期 4
·2489-2493
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IF 1.289
Zhen Yao,Li-wu Zhou,Bin-bin Dai,Kun Cao
Copolymer of dicyclopentadiene and cyclopentene (CPE) is synthesized through ring-opening metathesis polymerization using the second-generation Grubbs catalyst. The influences of monomer composition, catalyst concentration, and reaction temperature on gelification time and monomer conversion have been investigated. Furthermore, the reaction injection molding process is employed to produce the copolymer of dicyclopentadiene and CPE. It has been found that postcuring process is necessary to achieve 100% monomer conversion. The incorporation of a small amount of CPE into the copolymers can reduce the weight loss rate in the TGA process and improve the mechanical properties. The effects of CPE fraction, catalyst concentration, and postcuring temperature on thermal stability and mechanical properties are discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
研究领域:
高分子化学
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材料科学
✓ 已验证
DOI
高影响因子
NEW JOURNAL OF CHEMISTRY
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2023
·Vol. 47
·期 17
·8391-8398
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IF 3.3
Penghui Li,Huixiang Wang,Junhua Gao,Liancheng Wang,Jing Shi,Yu Meng,Junfen Li,Baoliang Lv
Supported tungsten oxide catalysts are promising candidates for olefin epoxidation with hydrogen peroxide (H2O2). Understanding the structure–activity relationship is of great importance for developing more efficient tungsten oxide-based catalysts. Herein, WO3–SBA-15 with an isolated tetrahedron WO4 is synthesized using a direct incorporation strategy, and its TOF is 191 h−1 in cis-cyclooctene epoxidation with H2O2, which is much higher than that of WO3/SBA-15 (51 h−1) prepared using an impregnation method and that of bulk-WO3 (0.4 h−1). Its lowest apparent activation energy of 34.6 kJ mol−1 also corresponded to the remarkable performance of WO3–SBA-15. Kinetic analysis indicated that WO3–SBA-15 bound H2O2 more strongly than other catalysts, resulting in the facilitated activation of H2O2. By correlating the specific activity and the structure characterization, we considered that the high reactivity of WO3–SBA-15 was attributed to (i) more isolated WO4 sites, which were of benefit to the coordination and activation of H2O2 and (ii) a stronger metal–support interaction derived from isolated WO4 species, which favored the dissociation of an O–O bond in the W–OOH intermediate and contributed to the insertion of an oxygen atom into an olefin double bond. Furthermore, DFT calculations indicated that the isolated tungsten oxide was beneficial for lowering the energy barrier of electrophilic oxygen atom transfer, thereby facilitating epoxidation.
研究领域:
催化化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
Inorganic Chemistry Frontiers
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2018
·Vol. 5
·期 10
·2493-2500
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IF 5.106
Xiaoling Lin,Mengling Zhang,Mengmeng Zhu,Hui Huang,Chunfeng Shi,Yang Liu,Zhenhui Kang
Epoxides are an extremely important class of chemical intermediates in the chemical industry due to the versatility of epoxides in preparing many fine and specialty chemicals. However, designing more active and selective heterogeneous catalysts in epoxidation is still a priority and a challenge. In this work, we demonstrate the synthesis of two new Ag/polyoxometalate-based coordination polymers (Ag8(mttz)4(H2O)[PWVWVI11O40]·H2O (1) and Ag8(mttz)4(H2O)[PMoVMoVI11O40] (2), mttz = 5-methylthio-2H-tetrazole) that are highly active for the selective oxidation of cis-cyclooctene to epoxycyclooctane under mild conditions (solvent-free, atmospheric pressure, 70 °C with H2O2 as the oxidant under visible light). It is worth noting that compound 1 possesses abundant exposed active edge sites of Ag, resulting in the catalytic performance achieved in the selective oxidation of cis-cyclooctene to epoxycyclooctane being superior to its components (metal, polyoxometalates and ligand) and compound 2 with the conversion/selectivity to epoxycyclooctane of 70.15/99.68%, respectively. The excellent photocatalytic activity of compound 1 should be attributed to the synergy of the components after coordination polymerization and its structure with exposed active edge sites of Ag.
研究领域:
材料化学
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催化化学
✓ 已验证
DOI
高影响因子
MACROMOLECULES
·
2014
·
IF 5.927
Zhi-Qiang Jiang,Ya-Xin Xue,Jia-Li Chen,Zhi-Peng Yu,Na Liu,Jun Yin,Yuan-Yuan Zhu,Zong-Quan Wu
An air-stable phenylethynyl Pd(II) complex containing a polymerizable norbornene unit was designed and synthesized. Such a Pd(II) complex can initiate the living/controlled polymerization of phenyl isocyanide, giving stereoregular poly(phenyl isocyanide)s in high yields with controlled molecular weights and narrow molecular weight distributions. The norbornene unit on the Pd(II) complex can undergo ring-opening metathesis polymerization (ROMP) with Grubbs’ second-generation catalyst, affording polynorbornene bearing Pd(II) complex pendants under a living/controlled manner. Interestingly, the Pd(II) complex pendants on the isolated polynorbornene are active enough to initiate the living/controlled polymerization of phenyl isocyanides, yielding well-defined brush-like copolymers with polynorbornene backbone and helical poly(phenyl isocyanide) as side chains. 31P NMR analyses indicate almost all the Pd(II) units on the polynorbornene participated in the polymerization, and the grafting density of the brush copolymer is high. Further studies revealed the brush copolymer can be readily achieved in one-pot via tandem catalysis. By using this method, a range of brush copolymers with different structures and tunable compositions were facilely prepared in high yields with controlled molecular weights and narrow molecular weight distributions. The synthesized brush copolymers were revealed to form worm-like cylindrical morphologies and helical rod architectures in film state by atomic force microscope observations.
研究领域:
高分子化学
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材料科学
✓ 已验证
DOI
高影响因子
CRYSTAL GROWTH & DESIGN
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2023
·
IF 3.8
Shen Yu,Ming-Hui Sun,Yuan-Yuan Wang,Zhan Liu,Jia-Min Lyu,Yi-Long Wang,Zhi-Yi Hu,Yu Li,Li-Hua Chen,Bao-Lian Su
The epoxidation reaction over titanium silicalite-1 (TS-1) zeolites is a green way to produce epoxides that are important intermediates for chemicals. Nevertheless, the conventional microporous TS-1 zeolite shows limited diffusion ability for bulky molecules, leading to poor activity and low selectivity. Constructing hierarchical porosity in microporous materials is an effective strategy to enhance the diffusion properties of catalysts. However, there are few reports on the design and synthesis of TS-1 zeolites with hierarchical structure featuring multilevels, interconnectivity, and regularity for efficient diffusion and epoxidations. Herein, hierarchical TS-1 zeolites with ordered macro–meso–microporosity (OMMM-TS-1) are obtained by a method combining a templated effect of ordered macro–mesoporous matrices and a confined in situ crystallization process. The OMMM-TS-1 possesses ordered macropores with tunable size (∼200–600 nm), ordered mesopores (∼8 nm), and intact micropores (∼0.5 nm). The OMMM-TS-1 achieves a cyclooctene conversion as 3.6 times and 1.8 times and a selectivity to epoxy product as 1.6 times and 1.3 times higher than the conventional TS-1 (C-TS-1) and nanosized TS-1 (Nano-TS-1) zeolites, respectively. The OMMM-TS-1 also outperforms the C-TS-1 and Nano-TS-1 zeolites in epoxidations of a series of alkenes. Such a novel hierarchical structure can be applied in the design and synthesis of many other catalysts.
研究领域:
化学
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材料科学
·
催化
✓ 已验证
产品关联
DOI
高影响因子
POLYMER
·
2017
·
IF 3.684
Zi-Long Li,Fu-Rong Zeng,Hao-Cheng Li,Wei-Li Zeng,Hang-Chang Cai,Hong Jiang
Two distinct synthetic methodologies to furnish polynorbornene bearing thiol-maleimide adduct side groups, namely direct ring-opening metathesis polymerization (ROMP) of prefunctionalized monomers and postpolymerization modification, were investigated and compared in this study. ROMP of thiol-maleimide adduct-containing monomers M1 - M4 was performed to yield polymers PM1 - PM4 with full conversion of monomers but broad molecular weight distribution . Meanwhile, narrowly distributed polymers P1 - P4 were generated through postpolymerization modification of polymer P0 by using thiol-maleimide reaction. However, removal of residual monomer M0 was an indispensable step prior to postpolymerization modification since incomplete monomer conversion was observed in the previous step, synthesis of polymer P0 using ROMP of maleimide-containing monomer M0 . Narrow molecular weight distribution in conjunction with good polymerization controllability renders the strategy of postpolymerization modification a seemingly more reliable synthetic protocol to achieve the goal of this contribution. Finally, polymers P0 - P4 were subjected to property studies to elucidate their thermal stability, glass transition behavior, wettability and gelation using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angle measurement, and cross-linking test, respectively.
研究领域:
高分子化学
·
材料科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）