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21.
Bentolhoda Hadavi Moghadam Akbar Khodaparast Haghi Shohreh Kasaei 《Journal of Macromolecular Science: Physics》2015,54(11):1404-1425
Comparative studies between response surface methodology (RSM) and artificial neural network (ANN) methods to find the effects of electrospinning parameters on the porosity of nanofiber mats is described. The four important electrospinning parameters studied included solution concentration (wt.%), applied voltage (kV), spinning distance (cm) and volume flow rate (mL/h). It was found that the applied voltage and solution concentration are the two critical parameters affecting the porosity of the nanofiber mats. The two approaches were compared for their modeling and optimization capabilities with the modeling capability of RSM showing superiority over ANN, having comparatively lower values of errors. The mean relative error for the RSM and ANN models were 1.97% and 2.62% and the root mean square errors (RMSE) were 1.50 and 1.95, respectively. The superiority of the RSM-based approach is due to its high prediction accuracy and the ability to compute the combined effects of the electrospinning factors on the porosity of the nanofiber mats. 相似文献
22.
Juan A. Allegretto Agustín Iborra Dr. Juan M. Giussi Dr. Catalina von Bilderling Dr. Marcelo Ceolín Dr. Sergio Moya Dr. Omar Azzaroni Dr. Matias Rafti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(54):12388-12396
This work reports on a novel and versatile approach to control the structure of metal–organic framework (MOFs) films by using polymeric brushes as 3D primers, suitable for triggering heterogeneous MOF nucleation. As a proof-of-concept, this work explores the use of poly(1-vinylimidazole) brushes primer obtained via surface-initiated atom transfer radical polymerization (SI-ATRP) for the synthesis of Zn-based ZIF-8 MOF films. By modifying the grafting density of the brushes, smooth porous films were obtained featuring inherently hydrophobic microporosity arising from ZIF-8 structure, and an additional constructional interparticle mesoporosity, which can be employed for differential adsorption of targeted adsorbates. It was found that the grafting density modulates the constructional porosity of the films obtained; higher grafting densities result in more compact structures, while lower grafting density generates increasingly inhomogeneous films with a higher proportion of interparticle constructional porosity. 相似文献
23.
Ikjin Kim Dr. Avinash Dhamija Dr. In-Chul Hwang Hochan Lee Dr. Young Ho Ko Prof. Dr. Kimoon Kim 《化学:亚洲杂志》2021,16(20):3209-3212
Here, we report the synthesis of a truncated cone-shaped triangular porphyrinic macrocycle, P3L3 , via a single step imine condensation of a cis-diaminophenylporphyrin and a bent dialdehyde-based linker as building units. X-ray diffraction analysis reveals that the truncated cone-shaped P3L3 molecules are stacked on top of each other by π⋯π and CH⋯π interactions, to form 1.7 nm wide hollow columns in the solid state. The formation of the triangular macrocycle is corroborated by quantum chemical calculations. The permanent porosity of the P3L3 crystals is demonstrated by several gas sorption experiments and powder X-ray diffraction analysis. 相似文献
24.
Considering intrinsic properties of conjugated polyfluorenes and special functions of porous polymers, synthesis of fluorinated porous poly(spirobifluorene) via direct C?H arylation polycondensation is explored. Owing to the contorted structure and cross-linking nature, the obtained polymer FPSBF shows permanent porosities with Brunauer–Emmett–Teller specific surface area up to 700 m2 g?1 and exhibits a narrow pore size distribution with the dominant pore size at about 0.63 nm, which is more suitable for adsorption of small gas molecules. Based on the measured gas physisorption isotherms with pressure up to 1.13 bar, the obtained polymer shows good uptaking capacities for hydrogen (1.30 wt% at 1.0 bar and 77 K) and methane (4.80 wt% 1.0 bar and 273 K). Moreover, FPSBF has significant adsorption selectivity for CH4 against N2 and the estimated ideal adsorption selectivity ratio is up to 30/1 at 1.0 bar and 273 K, which makes the material possess potential application in gas separation. 相似文献
25.
Dr. Hui Liu Dr. Yonggang Zhao Zhijuan Zhang Nour Nijem Prof. Dr. Yves J. Chabal Prof. Dr. Xiangfang Peng Prof. Dr. Heping Zeng Prof. Dr. Jing Li 《化学:亚洲杂志》2013,8(4):778-785
We report two new 3D structures, [Zn3(bpdc)3(2,2′‐dmbpy)] (DMF)x(H2O)y ( 1 ) and [Zn3(bpdc)3(3,3′‐dmbpy)]?(DMF)4(H2O)0.5 ( 2 ), by methyl functionalization of the pillar ligand in [Zn3(bpdc)3(bpy)] (DMF)4?(H2O) ( 3 ) (bpdc=biphenyl‐4,4′‐dicarboxylic acid; z,z′‐dmbpy=z,z′‐dimethyl‐4,4′‐bipyridine; bpy=4,4′‐bipyridine). Single‐crystal X‐ray diffraction analysis indicates that 2 is isostructural to 3 , and the power X‐ray diffraction (PXRD) study shows a very similar framework of 1 to 2 and 3 . Both 1 and 2 are 3D porous structures made of Zn3(COO)6 secondary building units (SBUs) and 2,2′‐ or 3,3′‐dmbpy as pillar ligand. Thermogravimetric analysis (TGA) and PXRD studies reveal high thermal and water stability for both compounds. Gas‐adsorption studies show that the reduction of surface area and pore volume by introducing a methyl group to the bpy ligand leads to a decrease in H2 uptake for both compounds. However, CO2 adsorption experiments with 1′ (guest‐free 1 ) indicate significant enhancement in CO2 uptake, whereas for 2′ (guest‐free 2 ) the adsorbed amount is decreased. These results suggest that there are two opposing and competitive effects brought on by methyl functionalization: the enhancement due to increased isosteric heats of CO2 adsorption (Qst), and the detraction due to the reduction of surface area and pore volume. For 1′ , the enhancement effect dominates, which leads to a significantly higher uptake of CO2 than its parent compound 3′ (guest‐free 3 ). For 2′ , the detraction effect predominates, thereby resulting in reduced CO2 uptake relative to its parent structure 3′ . IR and Raman spectroscopic studies also present evidence for strong interaction between CO2 and methyl‐functionalized π moieties. Furthermore, all compounds exhibit high separation capability for CO2 over other small gases including CH4, CO, N2, and O2. 相似文献
26.
Harald Rennhofer Janea Khnke Jozef Keckes Johannes Tintner Christoph Unterweger Thomas Zinn Karl Deix Helga Lichtenegger Wolfgang Gindl-Altmutter 《Molecules (Basel, Switzerland)》2021,26(7)
Application of low-cost carbon black from lignin highly depends on the materials properties, which might by determined by raw material and processing conditions. Four different technical lignins were subjected to thermostabilization followed by stepwise heat treatment up to a temperature of 2000 °C in order to obtain micro-sized carbon particles. The development of the pore structure, graphitization and inner surfaces were investigated by X-ray scattering complemented by scanning electron microscopy and FTIR spectroscopy. Lignosulfonate-based carbons exhibit a complex pore structure with nanopores and mesopores that evolve by heat treatment. Organosolv, kraft and soda lignin-based samples exhibit distinct pores growing steadily with heat treatment temperature. All carbons exhibit increasing pore size of about 0.5–2 nm and increasing inner surface, with a strong increase between 1200 °C and 1600 °C. The chemistry and bonding nature shifts from basic organic material towards pure graphite. The crystallite size was found to increase with the increasing degree of graphitization. Heat treatment of just 1600 °C might be sufficient for many applications, allowing to reduce production energy while maintaining materials properties. 相似文献
27.
Dr. Alexander Sachse Caroline Wuttke Dr. Elízio Lissner Dr. Michèle Oberson de Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):14996-14999
Hierarchically porous ZSM‐5 was achieved by using a simple bottom‐up strategy combining zeolite seeds with imidazolium‐based ionic liquids. The bimodal ZSM‐5 with hexagonal arranged mesopores (3 nm) shows important activity in the acid catalysis of bulky compounds relative to conventional ZSM‐5. 相似文献
28.
Dr. Paul S. Wheatley Dr. Pavla Chlubná‐Eliášová Dr. Heather Greer Prof. Wuzong Zhou Dr. Valerie R. Seymour Dr. Daniel M. Dawson Prof. Sharon E. Ashbrook Dr. Ana B. Pinar Dr. Lynne B. McCusker Dr. Maksym Opanasenko Prof. Jiří Čejka Prof. Russell E. Morris 《Angewandte Chemie (International ed. in English)》2014,53(48):13210-13214
Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure‐directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneable surface area and micropore volume over a wide range can be prepared. This means that a particular surface area or micropore volume can be precisely tuned. The range of porosity we can target covers the whole range of useful zeolite porosity: from small pores consisting of 8‐rings all the way to extra‐large pores consisting of 14‐rings. 相似文献
29.
Ivana Brekalo David E. Deliz Leonard J. Barbour Michael D. Ward Tomislav Fri
i K. Travis Holman 《Angewandte Chemie (International ed. in English)》2020,59(5):1997-2002
Guanidinium organosulfonates (GSs) are a large and well‐explored archetypal family of hydrogen‐bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4‐benzenedisulfonate ( p ‐G2BDS ). p ‐G2BDS is obtained from its acetone solvate, AcMe@ G2BDS , by single‐crystal‐to‐single‐crystal (SC‐SC) desolvation, and exhibits a Type I low‐temperature/pressure N2 sorption isotherm (SABET=408.7(2) m2 g?1, 77 K). SC‐SC sorption of N2, CO2, Xe, and AcMe by p ‐G2BDS is explored under various conditions and X‐ray diffraction provides a measurement of the high‐pressure, room temperature Xe and CO2 sorption isotherms. Though p ‐G2BDS is formally metastable relative to the “collapsed”, nonporous polymorph, np ‐G2BDS , a sample of p ‐G2BDS survived for almost two decades under ambient conditions. np ‐G2BDS reverts to zCO2@ p ‐G2BDS or yXe@ p ‐G2BDS (y,z=variable) when pressure of CO2 or Xe, respectively, is applied. 相似文献
30.