JOURNAL OF POLYMER SCIENCE
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2020
·Vol. 58
·期 7
·969-976
·
IF 0
Guangtao Qian,Haiquan Chen,Guangliang Song,Jianan Yao,Mengjie Hu,Chunhai Chen
To introduce intramolecular hydrogen bonds in the polyimides (PIs), 5(6)-amino-2-(5-aminopyridin-2-yl)-benzimidazole (PyPABZ) were designed and synthesized. The intramolecular interaction was indicated by Fourier transform infrared when different copolyimides were prepared with 4,4′-oxydianiline and PyPABZ. These modified poly(benzimidazole imide)s eliminate the problem of high water absorption for benzimidazole (BI)-containing PIs in the materials applications. Moreover, the high packing coefficient and rigidity of these copolyimides caused by the strong intramolecular interaction from the H-bonding and the resulting PIs exhibited outstanding thermal properties such as high glass-transition temperature ( T g ) and low coefficient of thermal expansion. Graphical The polyimides derived from 5(6)-amino-2-(5-aminopyridin-2-yl)-benzimidazole (PIs–PyPABZ) were achieved with the presence of intramolecular hydrogen bonding. These modified co-poly(benzimidazole imide)s exhibited lower H 2 O-absorption and higher thermal properties depending on the intramolecular H-bonding content.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2020
·
IF 3.573
Yuan Liu,Yunyan Peng,Jun Luo,Jingkai Liu,Xiaoqing Liu
A bridging group is an indispensable element for the preparation of diphenol-based benzoxazines, and inevitably, its electronic features will affect the H-bond formation of obtained benzoxazine, which is a crucial factor that not only makes a difference on curing behaviors of benzoxazine but also poses significant influence on the performances of cured resins. However, systematical investigation about the effects of the bridging group on the H bonds in benzoxazine is still in a barren state. Herein, we bridge the gap with three high-purity model benzoxazine monomers. The results showed that electron-donating bridge groups made the benzoxazine monomers tend to start the curing reaction earlier, whereas the electron-withdrawing bridging groups had the opposite effect. In addition, it was also confirmed that the H bonds in polybenzoxazine could be readily tailored by carefully selecting the bridge groups of aromatic diphenols. In this work, some basic characteristics about benzoxazine have been revealed, which are helpful for us to understand its structure–properties relationship more deeply.
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Journal of Cleaner Production
·
2020
·
IF 7.246
Bowei Shen,XueJun Yu,Farong Zhang,Wenxiu Jiang,Hui Yuan,Zhiquan Pan,Hong Zhou
A new method of the catalytic alcoholysis of Dioscorea zingiberensis C. H. Wright into diosgenin by magnetic solid acid in a Teflon-lined stainless-steel autoclave for the first time. The magnetic solid acid, Fe 3 O 4 @SiO 2 –SO 3 H, was prepared by the connecting the –SO 3 H groups on the surface of SiO 2 encapsulated Fe 3 O 4 microspheres . The synthesized catalysts were systematically analyzed by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analyzer (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), temperature programmed desorption of ammonia (NH 3 -TPD), scanning electron microscope (SEM), transmission electron microscope (TEM) and transmission electron microscope-mapping(TEM-mapping). To obtain the best conditions for the alcoholysis of Dioscorea zingiberensis C. H. Wright, single factor test was first utilized to determine the range of optimal conditions and optimized by response surface method . A three-level-three-factor Box-Behnken design was adopted to illustrate the effect of solid acid mass, solvent volume, reaction time and temperature on the yield of diosgenin. The optimum conditions obtained by response surface methodology were: 0.42 g Fe 3 O 4 @SiO 2 –SO 3 H, 4.38 mL solvent of ethanol, the reaction temperature at 100 °C and 6.09 h reaction time. At the optimal conditions, this method can reach the highest yield 2.64% from Dioscorea zingiberensis C. H. Wright. The yield of the new method was 21.66% higher than conventional sulfuric acid hydrolysis based on the analysis results of UV and HPLC. Importantly, the catalysts and solvents used in the alcoholysis process by the solid acid can be recovered, which is green and environmentally friendly, indicating that the catalytic alcoholysis with magnetic solid acid under hydrothermal conditions had a broad application prospect in diosgenin production.
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CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Peng Hu,Jun Han,Jie Zhou,Hao Wang,Chao Xiong,Hao Liu,Xiantai Zhou,Yongqing Wang,Hongbing Ji
Efficient separation of propylene/propane (C 3 H 6 /C 3 H 8 ) is an imperative and extremely challenging process in the petrochemical industry due to their similar physicochemical characters. Known tactics mainly concentrate on unilateral thermodynamic or kinetic driven. Here, we report the efficient separation of C 3 H 6 /C 3 H 8 through cooperative equilibrium-kinetic synergetic effect in a nodes-engineered Zr-MOF scaffold (1to). The grafted -CF 3 motif with different isomers and resultant aperture chemistry awards 1to a late-model paradigm for efficient separation of C 3 H 6 /C 3 H 8 . Detailly, confined -CF 3 group having the role of H-bonding acceptor can result in improved adsorption enthalpy ( Q st ) of 38.1 kJ mol −1 , ideal adsorbed solution theory (IAST) selectivity of 80 and experimental selectivity of 25, respectively, indicating a marked thermodynamic driven for trapping C 3 H 6 . Besides, the contracted cross-sectional size and eligible pore shape of 1to could be judiciously adjusted through rationally engineering the pore microenvironment, yielding a topmost simulated diffusion selectivity of 408, which was 40.8 times higher than that of the pristine 1 example (10), effectively enabling the swift diffusion behavior of C 3 H 6 . Modeling simulations and breakthrough experiments confirmed the excellent C 3 H 6 /C 3 H 8 separation performance of 1to. This work successfully developed a novel nodes-engineered strategy for C 3 H 6 capture through equilibrium-kinetic synergetic effect, anticipating to set a new benchmark for gas separation and affording constructive guidance for tailoring delicate aperture chemistry.
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ACS Catalysis
·
2021
·
IF 13.084
Xiangdong Long,Jia Wang,Guang Gao,Chao Nie,Peng Sun,Yongjie Xi,Fuwei Li
Direct oxidative amination of the sp3 C–H bond is an attractive synthesis route to obtain amides. Conventional catalytic systems for this transformation are based on transition metals and complicated synthesis processes. Herein, direct and efficient oxidative amination of the methyl C–H bond in a wide range of N-heterocycles to access the corresponding amides over metal-free porous carbon is successfully developed. To understand the fundamental structure–activity relationships of carbon catalysts, the surface functional groups and the graphitization degree of porous carbon have been purposefully tailored through doping with nitrogen or phosphorus. The results of characterization, kinetic studies, liquid-phase adsorption experiments, and theoretical calculations indicate that the high activity of the carbon catalyst is attributed to the synergistic effect of surface acidic functional groups (hydroxyl/carboxylic acid/phosphate) and more graphene edge structures exposed on the surface of carbon materials with a high graphitization degree, in which the role of acidic functional groups is to adsorb the substrate molecule and the role of the graphene edge structure is to activate O2.
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JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
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2021
·
IF 8.067
Yunwei Liu,Zelin Chen,Chang Liu,Jinfeng Zhang,Wenbin Hu,Yida Deng
We have developed an efficient strategy to synthesize an active and durable electrocatalyst of Pd hydride nanocubes (NCs). Instead of the traditional chemical method, the PdH 0.43 NCs are firstly prepared via a hydrogen diffusion procedure, followed by hydrothermal synthesis of an amorphous CuO layer encapsulating the PdH 0.43 NCs to prevent the hydrogen atoms from escaping. Obvious lattice expansion is demonstrated playing a pivotal role in the enhancement of their oxygen reduction reaction (ORR) activity and durability. The obtained PdH 0.43 @CuO NCs catalysts exhibit an ORR mass activity of 0.18 A mg −1 at 0.90 V versus reversible hydrogen electrode in an alkaline medium, which is about five times higher than that of commercial Pt/C. Accelerated durability tests show that there is only a 32 mV decay in half-wave potential even after 10,000 potential cycles, indicating the excellent stability of PdH 0.43 @CuO NCs. Density functional theory (DFT) calculations also indicate that, compared to Pd, PdH 0.43 has a lower limiting barrier to form OH − during the ORR process. The present study illustrates the importance of lattice expansion caused by hydrogen and offers an available strategy to design highly efficient and durable Pd-based electrocatalysts for alkaline fuel cells.
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JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
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2021
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IF 5.302
Fuhai Liu,Maozhong Yi,Liping Ran,Yicheng Ge,Zhe Zhou,Ke Peng
C/C-BN-SiC composite was prepared by ceramic slurry infiltration combined with resin impregnation and carbonization, and the matrix with continuous distributed self-healing phase was obtained. In this study, the kinetic characteristics and oxidation behavior of the composites with various h-BN/SiC ratios in the temperature range of 600∼1300°C were studied by combining the isothermal oxidation test with the kinetic model. The optimal h-BN/SiC ratio balances the thermal stability and fluidity of the oxidized product, which not only has high thermal stability and low oxygen permeability to acts as an oxygen diffusion barrier but also has a certain fluidity to seal defects.
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JOURNAL OF MASS SPECTROMETRY
·
2019
·Vol. 54
·期 3
·239-249
·
IF 2.267
Hua-Ming Xiao,Xian Wang,Xing Yang,Feng Zheng,Yu-Qi Feng
Hydralazine has been widely employed in the development of drugs, derivatization reagents, and ligands. In the present work, we reported a new type of dehydrogenated ion [M − H] + that was produced from the hydralazine derivative of hexanal in electrospray ionization mass spectrometry (ESI-MS). The formation of [M − H] + ions in the ESI-MS was found to be independent on the mobile phase composition of the liquid chromatography and ESI source parameters. A series of hydralazine derivatives of aldehyde were investigated to confirm this phenomenon. The results showed that hydralazine derivatives of aldehydes that contained an sp 3 hybridization carbon with a hydrogen at the α-position of aldehydes could form the unexpected [M − H] + ions, whereas hydralazine derivative of acetone could only generate [M + H] + ion in the ESI-MS. We proposed the possible formation mechanism of [M − H] + ion for the hydralazine derivatives of aldehydes: the [M − H] + ion was possibly formed by the loss a hydrogen molecule (H 2 ) from the protonated ion [M + H] + . The results obtained from density functional theory (DFT) calculations supported this proposed formation mechanism of [M − H] + ion.
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PubMed
高影响因子
Nanomaterials
·
2019
·Vol. 9
·期 7
·1051
·
IF 4.034
Xiu Wang,Zhihuai Yu,Liang Jiao,Huiyang Bian,Weisheng Yang,Weibing Wu,Huining Xiao,Hongqi Dai
Hexagonal boron nitride (h-BN)-based heat-spreading materials have drawn considerable attention in electronic diaphragm and packaging fields because of their high thermal conductivity and desired electrical insulation properties. However, the traditional approach to fabricate thermally conductive composites usually suffers from low thermal conductivity, and cannot meet the requirement of thermal management. In this work, novel h-BN/cellulose-nano fiber (CNF) composite films with excellent thermal conductivity in through plane and electrical insulation properties are fabricated via an innovative process, i.e., the perfusion of h-BN into porous three dimensional (3D) CNF aerogel skeleton to form the h-BN thermally conductive pathways by filling the CNF aerogel voids. When at an h-BN loading of 9.51 vol %, the thermal conductivity of h-BN/CNF aerogel perfusion composite film is 1.488 W·m−1·K−1at through plane, an increase by 260.3%. The volume resistivity is 3.83 × 1014Ω·cm, superior to that of synthetic polymer materials (about 109~1013Ω·cm). Therefore, the resulting h-BN/CNF film is very promising to replace the traditional synthetic polymer materials for a broad spectrum of applications, including the field of electronics.Keywords:CNF aerogel;perfusion;h-BN;thermal conductivity;electrical insulation
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高影响因子
BIOMETALS
·
2019
·Vol. 32
·期 2
·251-264
·
IF 2.455
Liu Xiao-Li,Ye Sen,Li Hua-Wei,Lu Bo,Yu Yan-Qin,Fan Yu-Peng,Yang Wei-Jun,Yang Jin-Shu
Rimicaris exoculata (Decapoda: Bresiliidae) is one of the dominant species among hydrothermal vent communities along the Mid-Atlantic Ridge. This shrimp can tolerate high concentrations of heavy metals such as iron, but the mechanisms used for detoxification and utilization of excess metals remain largely unknown. Ferritin is a major iron storage protein in most living organisms. The central heavy subunit of ferritin (H-ferritin) possesses ferroxidase activity and converts iron from Fe 2+ to Fe 3+ , the non-toxic form used for storage. In the present study, the H-ferritin RexFrtH was identified in the hydrothermal vent shrimp R. exoculata , and found to be highly expressed in the gill, the main organ involved in bioaccumulation of metals, at both RNA and protein levels. Accumulation of RexFrtH decreased from efferent to afferent vessels, coinciding with the direction of water flow through the gills. Fe 3+ was localized with RexFrtH, and in vitro iron-binding and ferroxidase assays using recombinant RexFrtH confirmed the high affinity for iron. Based on these results, we propose a model of iron metabolism in R. exoculata gills; ferrous iron from ambient hydrothermal water accumulates and is converted and stored in ferric form by RexFrtH as an iron reservoir when needed for metabolism, or excreted as an intermediate to prevent iron overload. The findings expand our understanding of the adaptation strategies used by shrimps inhabiting extreme hydrothermal vents to cope with extremely high heavy metal concentrations.
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高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2019
·
IF 4.084
Liangfeng Luo,Yidi Wang,Siping Huo,Peng Lv,Jun Fang,Yang Yang,Bin Fei
CuS/CdS(H)/CdS(C) photocatalysts were synthesized via the hydrothermal method by employing thiourea , Cd(CH 3 COO) 2 ·3H 2 O and copper 1,4-benzenedicarboxylate MOF (CuBDC). The photocatalysts were characterized by XRD , XPS , BET, TEM and UV–vis diffuse reflectance spectra. Interestingly, hexagonal CdS (CdS(H)) and cubic CdS (CdS(C)) were formed with phase junctions in one step when CuBDC was introduced in the synthesis process, in addition, CuS nanoparticles were deposited on CdS. However, only hexagonal CdS was obtained without CuBDC. It demonstrated that CuBDC was not only the precursor of CuS but also the structural modifier for CdS. With the reduction of re-combination of photo-induced electrons and holes caused by phase junctions and the enhancement of visible-light absorptions due to the loading of CuS, all CuS/CdS(H)/CdS(C) photocatalysts had higher photocurrent densities under visible-light irradiation, and consequently the higher rates of H 2 production than pure CdS(H). Typically, the catalyst with 2.89 wt% of Cu showed a highest rate of H 2 evolution at 2042 μmol/g/h.
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高影响因子
Journal of Physical Chemistry C
·
2018
·
IF 4.484
Zhiqiang Xie,Congbiao Chen,Bo Hou,Dekui Sun,Heqin Guo,Jungang Wang,Debao Li,Litao Jia
The nature of high-silica H–Y acid sites in dimethoxymethane carbonylation is investigated by NH3 poisoning with a combination of reaction results, diffuse reflection infrared Fourier transform spectra, and NH3 temperature-programmed desorption. After NH3 poisoning of H–Y, ammonia desorption of zeolites NH4–Y was conducted at different temperatures to obtain catalysts HNH4–Y that gradually exposed different acid sites. The zeolites thus produced catalyzed dimethoxymethane carbonylation with a linear dependence of the conversion on the ammonia desorption temperature before the plateau stage. It was observed that strong Brønsted acids in zeolite Y catalyzed the reaction more selectively toward the main product methyl methoxyacetate, and weak Brønsted acids catalyzed the reaction more selectively toward the byproduct methyl formate. Furthermore, the turnover frequency of Brønsted acids varied significantly among the Brønsted acids and decreased with acid strength. This finding suggested that only 10.1–18.3% of the total Al in zeolite Y with Si/Al ratios of 15, 30, and 40 contributed to the total framework Brønsted acids.
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