查看更多>>摘要：Tuning the morphological and acidic properties of mesoporous molecular sieve materials is highly valuable for catalyst design towards the reactions involving large molecules. In this work, a series of Ga-containing SBA-15 ordered mesoporous materials (OMMs) were synthesized following the acid-free strategy. Ga-SBA-15 exhibits an acid amount of 0.48 mmol/g, comparable to the Al-SBA-15 (0.45 mmol/g). In addition, it is found that the straight short stick particles of Al-SBA-15 integrally bended upon a replacement of Al with Ga and the tendency continuous with the incremental addition of gallium, until fully transforms into the highly dispersed isolated bending particles of Ga-SBA-15. Owing to the improved interparticle-type mesoporosity derived from the dispersed bending particles, the active sites on external surface are highly accessible for large molecules. As for the acidic property, the Bronsted-type acidic property of Al-SBA-15 changed to tne Lewis-type acidity with the replacement of gallium. In the Ga-SBA-15 case, more than 93% of strong acid sites were confirmed as Lewis characteristic. On the other hand, Low Density Polyethylene (LDPE) exhibits a faster decomposition rate over Ga-SBA-15 than Al-SBA-15 and Al-Ga bimetallic doped SBA-15 (galloaluminosilicate) catalysts.
查看更多>>摘要：Here different Ethanol-To-Hydrocarbons (ETH) reaction pathways on the external surface and in the channels of HZSM-5 were revealed by comparing the catalytic performance of ZSM-5 samples with different distributions of acidic type and location: including (1) SiO2(II)-NaZSM-5 with only internal Lewis (L) acidity, (2) NaZSM-5 with both internal and external L acidity, (3) SiO2(II)-HZSM-5 with only internal Bronsted (B) & L acidity, and (4) HZSM-5 with B & L acidity on both external and internal surface. The primary product was the ethylene from ethanol dehydration over NaZSM-5, SiO2(II)-NaZSM-5 and SiO2(II)-HZSM-5, which exhibited the much low se-lectivities of C_(3+). hydrocarbons. However, except C2 aliphatics, plenty of C_(3+) aliphatics and aromatics were generated over the HZSM-5 which showed a higher ethanol conversion. These results indicate the B acid sites on external surface are responsible for a high-efficiency conversion of ethanol/ethylene into C_(3+) hydrocarbons via double-cycle process, which cannot likely occur on the acidic internal-surface in micropores due to both the much low dimerization reactivity of ethylene and the severe space-restriction effect there. Both internal and external L acid sites are only involved in the catalytic ethanol dehydration, which is also catalyzed by internal and external B acidity. These reaction pathways on the external surface of HZSM-5 were further confirmed by the ETH reaction results over two mesoporous materials (i.e., γ-Al2O3 with only L acidity and B2O3-γ-Al2O3 with both L and B acidity).
查看更多>>摘要：The increasing complexity in composition and structure of modern porous nanocomposite materials requires the development of advanced technologies that allow the simultaneous treatment of dissimilar compounds, not only with unlike composition but also involving different classes of pores, e.g., micro and mesopores. This work shows that supercritical CO2 (scCO2) technology can be used as generic processing aid to obtain composites involving non-reduced graphene oxide (GO) and metal organic frameworks (MOFs) in the form of aerogels with hierarchical porosity. Hybrid aerogels are formed by either depositing (ex situ) or growing (in situ) MOF nanocrystals onto the surface of 2D GO nanosheets. The archetypal hydrophilic HKUST-1 and UiO-66 and hydrophobic ZIF-8 microporous MOFs are chosen to exemplify the method possibilities. The ex situ route was adequate to prepare hydrophilic MOFs@GO homogeneous composites, while the in situ approach must be used to prepare hydrophobic MOFs@GO aerogels. Moreover, the scCO2 methodology should be adjusted for each studied MOF in regard of the organic solvent used to disperse the nanoentities constituting the composite. The end-products are obtained in the form of aerogels mimicking the shape of the recipient in which they are contained. The products are characterized in regard of structure by X-ray diffraction, textural properties by low temperature N2 adsorption/desorption and morphology by electronic microscopy.
查看更多>>摘要：Metal-organic framework (MOF) derived nanozymes show significant promises in biosensing and biomedicine. Nanozymes are nanomaterial-based artificial enzymes. But how to improve the catalytic capacity of nanozymes in a simple manner is still a challenge. Herein, we demonstrated that the pore size/volume and catalytic capacity of Mn3O4 can be modulated by biomolecules biomineralized in Mn-MOF before calcination. The biomineralization-derived Mn3O4 shows larger pore size/volume and higher peroxidase/oxidase dual enzymatic activity compared to the pure Mn-MOF derived one. After loading with cholesterol oxidase, the prepared bio-inorganic hybrid nanozyme is able to detect the cholesterol in serum samples with high sensitivity. This work demonstrates that biomineralization of MOF with exogenous molecules is an ingenious and convenient strategy to synthetize nanozyme with high catalytic activity.
查看更多>>摘要：In this work, three different functionalized mesoporous silica nanoparticles (MSNs) were synthesized through the co-condensation synthesis in oil/water emulsion. Hexadecyltrimethoxysilane, triethoxy-3-(2-imidazolin-1-yl) propylsilane and (3-mercaptopropyl)triethoxysilane were used as organo-substituted silica precursors with variable molar ratio with respect to tetraethylorthosilicate (TEOS, 1:4,1:9,1:19). The occurred functionalization was investigated by Infrared Spectroscopy and FT-Raman and ~(29)Si {~1H} CP-MAS-NMR spectroscopy. Results show that the three materials were successfully functionalized. The influence of the different pendant groups and their concentration on the mesostructured pore organization of the obtained nanoparticles respect to the non-functionalized mesoporous silica was evaluated by means of Transmission Electron Microscopy and N2 sorption measurements. Bulky aliphatic C16 chains, especially in higher concentration, causes severe changes in mesoporous structure, leading to a more heterogeneous material. The imidazoline groups, instead, change the mesostructured morphology of the pores to an irregular but more interconnected one, while the presence of mercaptopropyl groups does not bring significant modifications. The different structural modifications in pore morphology observed between the samples is due to the different interactions between derivatized silica precursors and the components of the emulsion.
查看更多>>摘要：Phase formation upon hydrothermal crystallization of sodium titanosilicates has been studied in detail. It was shown that an excessive amount of Na and Si with respect to Ti affects the crystallization. It demonstrates that in a clear starting solution, high crystalline microporous titanosilicate (CST, Na2Ti2SiO7·2H2O) with sitinakite structure can be formed in 6 h and the crystallization is controlled by nucleation. With less amount of water, CST can be formed in 2 h. At low NaOH content, ETS-4 forms in 2 h at 230 °C. By simply increasing NaOH content in starting mixture, the crystallinity of CST improved. With increasing synthesis time CST re-crystallized to AM-4 with unusual hierarchal morphology. The synthesis temperature has a clear influence on the phase formation. At low synthesis temperature, a material with ivanyukite structure (GTS-1) was obtained in 4 h at 150 °C. Additionally, we discussed evidence for CST/GTS-1 intergrowths.
查看更多>>摘要：As one of the best candidates, lithium sulfur battery (Li-S) is extensively explored due to the high theoretical capacity and abundant sources of sulfur. Carbon-based materials take an important role as a host for sulfur in the cathode. In this paper, a nitrogen-doped hollow carbon for sulfur cathode (NHC-S) with high sulfur loading of 92% is studied for Li-S batteries. The structural characterization demonstrates that the N-doping can improve the graphitization of the hollow carbon material, which increases the electrical conductivity. The catalytic and deposition nucleation tests indicate that the N doping can increase the nucleation rate of Li2S, which is also illustrated by the larger binding energies of Li2S on N-doping substrates than on carbon via density functional theory (DFT) analysis. The initial specific capacity of NHC-S is 864.8 mAh g~(-1) at the current density of 0.2 C, and 460.8 mAh g~(-1) after 500 cycles. When the sulfur content loading was up to 2.8 mg cm~(-2), the electrode material could achieve 85% capacity retention after 100 reversible cycles.
查看更多>>摘要：One-step direct hydroxylation of aromatics is an atom-economic way for phenols production. Ti-containing MFI zeolite is considered to be one of the most potential catalysts for hydroxylation of aromatics to phenols under mild condition with aqueous H2O2 as the oxidant. However, the products are often a mixture of mono- or multi-phenols. Designing TS-1 zeolite catalyst with high yield and selectivity to the target phenols remains a challenging task. Here TS-1 zeolites are prepared by direct hydrothermal and post-synthetic methods. Multiple spectroscopic characterizations show that the crystallinity and Ti-Lewis acid sites (Ti-LASs) distribution of TS-1 zeolite can be controlled by the synthetic approach. The structure-activity relationship of TS-1 zeolite is established in the catalytic hydroxylation of anisole, revealing that Ti-LASs concentration determines the conversion of anisole, while both the crystallinity and Ti-LASs distribution significantly influence the selectivity to the desired product para-hydroxyanisole.
查看更多>>摘要：Hollow mesoporous organosilica nanoparticles (HMOSNPs) have provided unique opportunities to improve therapeutic efficacy of the encapsulated drugs due to versatile hybrid frameworks and tunable pore sizes, biodegradable nature and intelligent performance. In the current study, we have designed HMOSNPs capped with red blood cell (RBC) membrane to provide biomimetic RBC-coated HMOS platform with controlled glutathione (GSH)-responsive doxorubicin (DOX)-releasing performance. DNA aptamer against MUC-1 receptor was used to prepare the targeted system (Apt-RBC-HMOS@DOX) for the guided delivery of DOX to colorectal tumor cells. Experimental data indicated that MUCl aptamer could particularly facilitate drug uptake the designed biomimetic nanoparticles into HT29 and C26 cells. Moreover, targeted Apt-RBC-HMOS@DOX system remarkably enhanced tumor targeting capability in C26 tumor bearing mice compared to non-targeted RBC-HMOS@DOX and free drug. GSH-responsive Apt-RBC-HMOS@DOX system also reduced DOX-induced toxicity in terms of tumor growth suppression and survival rate, proposing its potential to translate in cancer therapy.
查看更多>>摘要：The emission of volatile organic compounds (VOCs) causes serious atmospheric environmental problems and catalytic combustion is one of the most promising methods in the treatment of VOCs. In this work, the Pt/Hp catalyst was fabricated via supercritical fluid deposition (SFD) for the first time and its activity was evaluated for toluene catalytic combustion. The preparation conditions during the SFD process were optimized. Na2PtCl6 was selected as the precursor and 450 °C as the reduction temperature. The catalysts prepared by the SFD and impregnation (IM) were compared. The Pt/Hp catalyst prepared by SFD had smaller size and higher dispersion and its T90 was 25 °C lower than that prepared by IM, which showed obvious size effect. For the similar activity, the Pt loading on catalyst prepared by SFD is only 50% of that on catalyst prepared by IM, showing obvious reduction effect for noble metal.
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