查看更多>>摘要：? 2021In the quest to increase the quality of life and life expectancy, there is a great demand to develop advanced medical devices capable of facing current health challenges. Santa Barbara Amorphous (SBA-15) mesoporous silica has been demonstrated to be a remarkable option for a variety of biomedical applications, from tissue engineering to drug delivery, due to its unique hierarchical porous structure. This work reports on the effect of using different ratios and concentrations of an acid mixture mediated by HCl/H3PO4 that in combination with a glycerol-modified silane precursor favoured obtaining bioactive SBA-15 mesoporous silica rods. The surfactant was removed by solvent extraction which allowed to keep a substantial amount of silanol groups (SiOH) at the surface. All the evaluated samples showed homogeneous rod shape and particle size, as well as high bioactivity after being immersed for 14 days in simulated body fluid (SBF). Different structural arrangements of needle-type carbonate hydroxyapatite (HCA) crystals were produced from SBA-15 upon immersion in SBF. By scanning electron microscopy (SEM) characterization, it was observed that rod-shaped SBA-15 materials displayed higher degradability when the concentration of H3PO4 was increased. An indirect cell viability assay with MC3T3-E1 osteoblast precursor cells was performed by incubating cells in cell culture medium exposed to SBA-15 particles for 1 and 4 days. The results obtained from the WST-8 assay and fluorescent staining showed no negative effect on cell viability, indicating a lack of cytotoxicity of the rod-like SBA-15 particles.
查看更多>>摘要：? 2021 Elsevier Inc.Lithium-ion batteries have been regarded as the most potential energy storage system due to their high energy density and theoretical capacity. However, conventional separators suffer from low electrolyte absorption, poor thermal and cycling stability, short circuits caused by dendrite growth. Herein, an effective approach was proposed to explore MOFs-based 3D-channeled separator via in-situ growth of ZIF-8 coating, which could significantly improve cycle stability and inhibit dendrite growth. Specifically, PLA membrane with 3D-channels was prepared by directional electrospinning and dopamine-induced assembling of MOFs in-situ growth onto the specified surface. By manipulating solvents, the desirable robustness of MOFs coatings could be accomplished through morphological assembly. Based on MOFs-architectured coating and microporosity, the excellent thermal stability (no change in size at 120 °C) and superior electrolyte uptake ability (290%) were finally obtained for the biobased separator. The assembled Li-ion battery exhibited ultrahigh cycle stability (capacity retention rate, 98.78% after 200 cycles at 1C rate) and preferable resistance to dendritic penetration, higher than those of the publicly reported. The excellent performance was attributed to the multiple 3D-channeled pathways for Li+ provided by MOFs and coating morphology. This study shows the potential for the development of next generation energy storage devices with excellent cycle stability.
查看更多>>摘要：? 2021The capacitive performances of carbon materials greatly rely on the porous structure and conductive network. However, the compromise of carbon materials with suitable porosity and 3D conductive framework still exists difficulty. Herein, a hierarchical porous free-standing carbon nano?ber (CNF) membrane was obtained from electrospun cellulose acetate (CA) nanofiber membrane via one-step carbonization and activation process. The influence of carbonization temperature on microstructure and electrochemical performance of carbons are investigated. The 800 °C carbonized sample CA-CNFs-800 exhibits large speci?c surface area of 720.8 m2 g?1 and suitable pore size distribution. The micropore dominated structure and three-dimensional conductive carbon networks enable fast electron/ion transport. The speci?c capacitance reaches 229.4 F g?1 at 0.2 A g?1 with good rate performance of 72.8% capacitance retention at 20 A g?1 for CA-CNFs-800. Moreover, CA-CNFs-800 possess high capacitance retention of 97.3% after 40,000 cycles at 20 A g?1. The CA-CNFs outperform other bio-based carbon materials, highlighting the great promise of CA-based CNFs for improving the capacitive performance of supercapacitors in electronic energy storage devices.
查看更多>>摘要：? 2021 Elsevier Inc.Although HZSM-5 zeolite is more and more widely used in petrochemical industry and other fields, its single narrow micropore system often leads to mass transfer issues during some types of catalytic reactions. In addition, dealumination in the presence of steam and coking due to the presence of strong acids sites are issues of aluminosilicate catalysts in general. In this work, a simple post-treatment method based on the traditional prepared HZSM-5 catalyst was proposed and an outlayer SiO2 encapsulated Gd/HZSM-5 catalyst with hollow and hierarchical porous systems (Si@Gd/Z5-T) was obtained. This catalyst can overcome those defects for the traditional HZSM-5 mentioned above, such as, the outermost SiO2 layer can protect the aluminum species in the framework of Gd/HZSM-5 and cover part of strong acid sites, and the hollow and hierarchical porous systems can minimize the mass transfer resistance, etc. The Si@Gd/Z5-T catalyst exhibited high selectivity of BTX (65.7%), especially xylene (39.7%), in the methanol to aromatics reaction (MTA) owing to the suitable acidity and optimized porous system. In addition, the Si@Gd/Z5-T catalyst possessed much better hydrothermal stability and the excellent anticoking ability in the MTA reaction as expected. Thus, this should be a general method for the modification of silica alumina molecular sieve catalysts to obtain the novel catalyst with hollow and hierarchical porous systems, adjustable acidity and high hydrothermal stability.
查看更多>>摘要：? 2021 Elsevier Inc.A series of low-sodium ultrastable Y zeolites (SiO2/Al2O3 ≈ 25) partially exchanged with different amounts of rare earth ions (RE2O3 = 0.55–3.32 wt%) was prepared and characterized by XRD, IR spectroscopy, elemental analysis, N2 adsorption, as well as 29Si and 27Al NMR. The effect of RE content on the number and relative strength of acid sites of REY zeolites was studied by IR spectroscopy of absorbed CO and pyridine. The increase in the RE content in the zeolites leads to a decrease in the concentration of strong Br?nsted acid sites (BAS) in faujasite cages (bridged Si–O(H)–Al groups), especially the concentration of stronger BAS associated with Si–O(H)–Al groups polarized by extra-framework aluminum species. At the same time, the concentration of less acidic OH groups connected with extra-framework ions increases possibly due to the formation of additional RE–O(H)–Al groups. The total number of BAS in all the samples remains close. An increase in the RE2O3 content from 0.55 to 3.32 wt% decreases almost by half the ratio of strong BAS in faujasite cages to less acidic extra-framework BAS. The catalytic performance of NiMo/(30 wt% REY + 70 wt% Al2O3) catalysts was evaluated in hydrocracking of vacuum gas oil. The enhanced hydrocracking activity and selectivity to middle distillates are mainly achieved due to the optimal acidity of the zeolites.
查看更多>>摘要：? 2021 The AuthorsBismuth-based metal-organic frameworks (Bi-MOFs) such as bismuth subgallate are important for applications ranging from medicine to gas separation and catalysis. Due to the porous nature of such Bi-MOFs, it would be valuable to understand their gas sorption and separation properties. Here, we present the gas sorption properties of three microporous Bi-MOFs, namely, CAU-17, CAU-33, and SU-101, along with a new trimesate-based structure, UU-200. We perform a detailed analysis of the sorption properties and kinetics of these Bi-MOFs. UU-200 shows good uptake capacities for CO2 (45.81 cm3 g?1 STP) and SF6 (24.69 cm3 g?1 STP) with CO2/N2 and SF6/N2 selectivities over 35 and 44, respectively at 293 K, 100 kPa. The structure of UU-200 is investigated using continuous rotation electron diffraction and is found to be a 3D porous framework containing pores with a diameter of 3.4–3.5 ?. Bi-MOFs as a group of relatively under-investigated types of MOFs have interesting sorption properties that render them promising for greenhouse gas adsorbents with good gas uptake capacities and high selectivities.
查看更多>>摘要：? 2021 Elsevier Inc.Chicken eggshell, a by-product of food processing, has been considered as natural waste and causes a major waste disposal problem. Recently, eggshell wastes have attracted great attention because of their rich calcium sources, and they can turn trash into treasure by rational use. In this work, peanut shell-like calcium carbonate (CaCO3) materials were synthesized with chicken eggshell biowastes as starting materials via coprecipitation method. CaCO3 materials were characterized by using XRD, SEM, XPS, and FTIR, respectively. The adsorption behavior of CaCO3 materials for Victoria blue B (VB) from aqueous solution was systematically investigated. The as-prepared hydrophilic CaCO3 materials show excellent adsorption performance for VB. The maximum adsorption capacity of CaCO3 at 35 °C is 1387 mg g?1. The kinetics and isotherm studies indicate that the absorption process follows the pseudo-second-order model and Langmuir isotherm model well. The thermodynamic parameters such as ΔG0, ΔH0 and ΔS0 show that the adsorption of VB onto CaCO3 materials is a spontaneous, endothermic and chemisorption process accompanied with an increase in entropy. The adsorption of VB onto CaCO3 materials is mainly controlled by electrostatic interaction. Thus, CaCO3 nanomaterial, as a hopeful adsorbent, can be used to efficiently remove VB in aqueous solution.
查看更多>>摘要：? 2021 The AuthorsHierarchical SAPO-11 molecular sieves were synthesized with three different mesopore structure directing agents (meso-SDAs): cetyltrimethylammonium bromide (CTAB), polyvinyl alcohol (PVA) and [3-(trimethoxysilyl) propyl] dimethyloctadecylammonium chloride (TPOAC). Two model reactions, methanol-to-hydrocarbons (MTH) and the Beckmann rearrangement (BMR) of cyclohexanone oxime, were employed to evaluate the pore topology and acid site locations of the hydrothermally synthesized hierarchical SAPO-11s. Initially, the modified porosity of the hierarchical SAPO-11s was thoroughly probed by employing a set of general characterization methods and by comparing the results to the conventional microporous C-SAPO-11. The nitrogen physisorption results revealed that CTAB-11 had a uniform distribution of mesopores centered at 2.8 nm, whereas the presence of mesopores in PVA-11 could not be convincingly resolved through conventional methods. Instead, the pore topology of PVA-11 was determined by utilizing model reactions, where the shape selective MTH model reaction revealed that the sample had mesopores present through an increased production of large products compared to the conventional C-SAPO-11. Additionally, the MTH model reaction showed that while PVA shifted the location of the Br?nsted acid sites (BAS) towards the mesopores, CTAB did not affect the BAS location of SAPO-11. Finally, the BMR model reaction elucidated the excellent intrapore connectivity of the hierarchical SAPO-11s through an increased lifetime compared to the conventional C-SAPO-11.
查看更多>>摘要：? 2021 Elsevier Inc.Silicon carbide (SiC) fibers are attractive for their thermal stability and chemical erosion resistance. However, the practical application of SiC fiber in the fields of thermal insulation is limited owing to its high intrinsic thermal conductivity. Herein, a novel closed cell structured SiC-based nanocomposite fiber (NCF) using hollow SiO2 nanospheres (HSNSs) as pore forming agent were designed by precursor conversion method combined with electrospinning technology. According to the content and size of HSNSs, NCFs with different pore size and porosity could be obtained. When the content of HSNSs reached 15%, a large number of closed cells were constructed inside the fiber, which broke the continuity of solid heat transfer and endowed it with excellent thermal insulation performance (～0.105 W m?1 K?1 at 1000 °C). Meanwhile, the NCFs showed excellent high-temperature resistance and mechanical properties, which makes it have a wide application prospect as a high temperature thermal insulator. This research also offers a new insight for the development of SiC-based fiber with multiple functions to meet various applications, such as catalyst supporters and microwave absorbers.
查看更多>>摘要：? 2021 Elsevier Inc.Herein, we successfully synthesized a 4-nitrobenzenesulfonyl (-O-SO2-Ph-NO2) functionalized Zr-UiO-66 MOF (1) material using 2-(((4-nitrophenyl)sulfonyl)oxy)terephthalic acid (H2BDC-O-SO2-Ph-NO2) linker and ZrCl4 metal salt under solvothermal reaction conditions. The MOF material displayed high thermal stability up to 370 °C under air atmosphere and considerable chemical stability in H2O, 1(M) HCl, acetic acid and aq. NaOH solution (pH 8 to 10). It also showed a large BET surface area of 1000 m2g-1 with a pore volume of 0.57 cm3g-1. The thermally activated MOF (1′) suspension displayed good selectivity towards the sensing of hydrazine (NH2NH2) in water. Together with rapid response time (4 min), 1′ displayed lowest ever limit of detection (52 ± 4 nM) of NH2NH2 among all the reported MOF based sensing probes of NH2NH2. Sensing of NH2NH2 in environmental water samples and MOF coated paper strips made it an extraordinary sensor of NH2NH2. The most interesting aspect of this robust probe is that it is the first MOF based sensor, which can sense NH2NH2 in the vapor phase. The response time for the vapor phase sensing was 8 min. The removal of electron withdrawing 4-nitrobenzenesulfonyl group by the nucleophilic attack of NH2NH2 is the reason behind the turn-on sensing which was proved by 1H NMR spectroscopy and mass spectrometric analysis.
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