查看更多>>摘要：Covalent organic frameworks recently were utilized as membrane fillers for effective liquid mixture separation due to their intriguing structure. Though a facile dipcoating-wiping method, a melamine-based hybrid membrane was prepared where Chitosan (CS) was combined with SNW-1 (Schiff base network-1) on the surface of α-Al2O3 support followed by crosslinking with calcium ions, a dense SNW-1/CS layer with thickness of 550 nm was successfully fabricated for ethanol/water pervaporation. The hydrophilicity of melamine-based membranes surface was enhanced by SNW-1 incorporation with improved anti-swelling property and thermal stability. The porous structure of SNW-1 offered free volume and fast channels for water transport. Consequendy, the melamine-based membranes showed long-term stability and excellent separation factor of 373 with high permeance flux of 2.8 kg/(m~2·h).
查看更多>>摘要：Efficiency and sustainability of catalytic thin-film nanocomposite (TFN) membranes are crucially important for the reverse-osmosis performance of thin film composite (TFC) membranes in many fields. Herein, Ag@UiO-66-NH2 catalytic nanoparticles were fabricated and incorporated into the polyamide active layer through by co-valent bond via the interfacial polymerization (IP) method. Polyamide TFN membranes with high efficiency, sustainable catalytic degradation of Rhodamine B (RhB), and excellent self-cleaning performance were prepared conveniently. The 0.8 wt % Ag@UiO-66-NH2 composite membrane has excellent permeability stability, and the flux recovery rate can reach 81.6% after 7 runs. In addition, the degradation rate of RhB can reach 99.6% by using this membrane. More importantly, the degradation efficiency of 250 mL RhB solution can still reach 94.5% after 7 cycles of catalytic test. The degradation effect of RhB by the TFN membranes was enhanced significantly owing to the synergistic effect of the adsorption and catalytic properties of Ag@UiO-66-NH2 nanoparticles. Moreover, it provides a universal method for preparing TFN membrane with a catalytic active layer, which can be applied in other fields of catalytic film by replacing Ag NPs with other particles.
查看更多>>摘要：Sn-Beta is a good solid Lewis acid catalyst. Seed-assisted hydrothermal synthesis is a popular method for its preparation. However, the mechanism of seeds in the crystallization process is not clear. Here, the role of seeds in the growth of crystal and the influence on the properties of the corresponding products were studied. The seeds and gel was characterized by XRD, SEM, FT-IR and TG. During the crystallization, it was observed that the seeds were partially dissolved and formed seed fragments in the initial stage. Then the seed fragments acted as the core of the crystals and promoted the crystallization process. Seeds greatly decreased the crystal size of the products as compared with the direct hydrothermal method in absence of seeds. The acidity and catalytic performance of Sn-Beta synthesized via seeds route are similar with those of none-seeds method.
查看更多>>摘要：Lanthanum microporous frameworks (Hdma)_(2n)[La2(1,3-pdta)2(H2O)2]n·5nH2O (1, dma = dimethylamine, 1,3-pdta = 1,3-propanediaminetetraacetic acid) and (H2pn)n[La2(1,3-pdta)2(H2O)2]n·5nH2O (2, pn = 1,3-propane-diamine) with double channels have been template-synthesized by protonated dimethylamines and 1,3-propane-diamines, respectively. While bulky product (H2bn)[La2(1,3-pdta)2(H2O)4]·10H2O (3, bn = 1,4-butanediamine) is isolated as a dinuclear species with tetrahydrates, whose main anion can be served as a precursor for 1 and 2. Materials 1-3 are able to maintain their chemical and thermal stabilities to 200 °C based on TG and XRD analyses. Gas adsorptions demonstrate that MOFs 1 and 2 are amicable for O2 and CO2, while no adsorption has been observed for CH4, N2 or H2 respectively. The amounts of encapsulated CO2 in hydrophobic pores are dependent on the alkalinities of the diamines in the next confined hydrophilic holes, showing synergistic effects between double channels. For protonated dimethylamines and 1,3-propanediamines in 1 and 2, obvious downfield shifts have been found by solid-state ~(13)C NMR spectroscopies, along with clear red shifts in FT-IR spectra compared with free species. Moreover, captured CO2 inside 1 can be quantized by NMR measurements and IR spectroscopies under ambient condition. These all reflect the confinement effects of nano-environments.
查看更多>>摘要：Tunable porosity through hollow features at nanoscale in metal organic frameworks (MOFs) can lead to enormous applications especially in catalysis. Hollow ZIF-67/ZIF-8 (core/shell) frameworks have been synthesized using solvothermal synthesis in methanol, wherein preformed ZIF-67 nanocrystals have been used as core. Using this method, hollow core/shell frameworks have been synthesized by excavation of ZIF-67 core and concurrent deposition of ZIF-8 shell for varying time. The crystal structure and chemical bonding of the frameworks have been characterized using X-ray diffraction, FTIR and Raman spectroscopy. Morphology of the hollow frameworks has been investigated using FE-SEM and EDX. Positron annihilation lifetime spectroscopy in combination with small angle X-ray scattering have been used to characterize the multiscale pore architecture (ultramicropores to mesopores) of these hollow frameworks. The sodalite topology and associated pore architecture of ZIFs are retained during the synthesis of hollow framework, however the excavation of core leads to enhancement in mesopores. Hollow frameworks have been tested for their performance towards oxygen evolution reaction. The hollow frameworks show improvement in the catalytic activity as compared to pure ZIF-67 nanocrystals. It is proposed that in order to further improve their catalytic performance, post-synthesis modifications for enhancement in stability of pore network of shell and loading of active species are required.
查看更多>>摘要：Conjugated polymers (CPs) show enormous potential for photocatalytic degradation of antibiotics, but still exhibit unsatisfactory degradation rate due to the hydrophobicity. Herein, we report the designed synthesis of two visible-light-active triazine-cored CPs and their photocatalytic activities in tetracycline (TC) degradation. Interestingly, the hydrophilicity and opto-electronic properties of CPs can be readily tuned by selection of building blocks attached diverse side-chains. For CPs bearing photoactive center, the integration of 2-methoxye-thoxy functional groups can prominently improve the hydrophilicity and reduce undesirable aggregation, which facilitates the adsorption of contaminants for the subsequent photodegradation reaction. Moreover, the embedded 2-methoxyethoxy moieties render the resulting CPs with narrower band gap, higher visible light-harvesting efficiency and charge carrier mobility, thus favoring the enhanced photocatalytic performance. As such, the CP involving 2-methoxyethoxy (BMTA-TAPT) has a higher photodegradation kinetic of TC, which is over 9 times the rate of the hydrophobic counterpart (TA-TAPT). The results provide a simple and effective approach for engineering high-performance polymer photocatalysts.
查看更多>>摘要：Materials sensitive to external stimuli are recognized as safe and effective tool able to respond to specific demands in the therapy of various diseases. Thermo sensitive hydrogels based on poly(N-isopropylacrylamide) (P (NIPAAM)) are widely investigated for targeted drug delivery. Still, the abundance of the stimuli in the human body often requires more than one responsive group able to act simultaneously to achieve optimal therapeutic effects. Due to its pH sensitivity and bio-based production, crotonic acid (CA) was a monomer of choice for preparation of eco-friendly copolymer hydrogels based on NIPAAM and CA (P(NIPAAMcoCA)), which turned to be thermo and pH sensitive at the same time. The potential of the P(NIPAAMcoCA) system for encapsulation and controlled release of drugs with different solubility was investigated engaging water-soluble lidocaine hydrochloride and poorly water-soluble ibuprofen as model drugs. The hydrogels were characterized by various technics: FTIR, DSC, SEM and single compressive tests, while swelling behavior and controlled release of the drugs were analyzed with respect to the CA amount in two environments with different pH values at 25 °C and 37 °C. It was demonstrated that due to their dual responsiveness the P(NIPAAMcoCA) hydrogels have potential for controlled release of drugs with different solubility.
Lucas F.A.S. ZafanelliAdriano HenriqueHendryk Steldinger
13页
查看更多>>摘要：The applicability of 3D-printed activated carbons for their use to CO2 capture in post-combustion streams and the influence of activation conditions on CO2 uptake and CO2 to N2 selectivity were studied. For two monoliths with the same open cellular foam geometry but low and high burnoff during activation, a series of fixed-bed breakthrough adsorption experiments under typical post-combustion conditions, in a wide range of temperature (313 and 373 K), and partial pressure of CO2 up to 120 kPa were carried out. It is shown that the higher burnoff during activation of the 3D printed carbon enhances the adsorption capacity of CO2 and N2 due to the increased specific surface area with sorption uptakes that can reach 3.17 mol/kg at 313 K and 120 kPa. Nevertheless, the lower burnoff time on monolith 1 leads to higher selectivity of CO2 over N2, up to 18 against 10 on monolith 2, considering a binary interaction to a mixture of CO2/N2 (15/85 vol%) at 313 K. The single and multicomponent adsorption equilibrium is conveniently described through the dual-site Langmuir isotherm model, while the breakthrough curves simulated using a dynamic fixed-bed adsorption linear driving force model. Working capacities for the 3D printed carbon with lower burnoff time lead to the best results, varying of 0.15-1.1 mol/kg for the regeneration temperature 300-390 K. Finally, consecutive adsorption-desorption experiments show excellent stability and regenerability for both 3D printed activated carbon monoliths and the whole study underpins the high potential of these materials for CO2 capture in post-combustion streams.
查看更多>>摘要：Atomic layer deposition (AID) was used to prepare ZrO2 films on the surface of the mesoporous silica, SBA-15, and to modify the surface of these films with WO3 in order to form tungstated zirconia. Adsorption-desorption isotherms, pore size distributions, and transmission electron microscopy demonstrated that the AID synthesis produced zirconia films that were conformal to the SBA-15 pores. DRIFT spectroscopy of pyridine adsorbed on the tungstated-zirconia SBA-15 samples showed adsorbed pyridinium ions, confirming the presence of Br0nsted-acid sites on this material, consistent with what has been reported for bulk tungstated zirconia. The ALD-synthesized, tungstated-zirconia SBA-15 was also shown to be active in the acid-catalyzed H-D exchange between toluene and D2O.
查看更多>>摘要：Sorption in mesoporous media can induce either solid expansion or contraction, with the governing mechanism at molecular scale still unclear. The coupling between sorption and deformation is studied by an atomistic slit pore model with the help of molecular simulations. It is found that the sorption-induced deformation can shift between expansion and contraction by simply tuning the surface morphology. The underlying mechanism is revealed by a theoretical analysis conducted on a simplified two-dimensional model. It shows that the change in surface morphology alters the directions of atomistic forces between solid and fluid atoms, resulting in the change of sign of the strain. The theoretical analysis predicts that contraction happens on relatively smooth solid surfaces while expansion on corrugated surfaces, which is validated by molecular simulations. Moreover, roles of different solid-fluid interaction parameters on the coupling behavior are characterized. The interaction strength parameter influences the magnitude of the strain but has no effect on the sign, while the interaction distance parameter takes effect on both the magnitude and the sign. The current research explains both sorption-induced expansion and contraction and paves ways to material design for targeted sorption-induced deformation behavior.
NSTL