Preparation and characterization of metal-organic framework membranes for gas separation

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Improvement of hydrothermal stability of zeolitic imidazolate frameworks

The metal-organic framework ZIF-8, which undergoes hydrolysis under hydrothermal conditions, is endowed with high water-resistance after a shell-ligand-exchange-reaction. The stabilized ZIF-8 retains its structural characteristics with improved application performances in adsorption and membrane separation. © 2013 The Royal Society of Chemistry

Ethene/ethane separation by the MOF membrane ZIF-8: molecular correlation of permeation, adsorption, diffusion

The newly developed MOF membrane ZIF-8 separates an equimolar ethene/ethane mixture at room temperature for 1 and 6 bar feed pressure, respectively, with a selectivity of 2.8 and 2.4. Independent sorption uptake studies of an ethene/ethane mixture on a big ZIF-8 single crystal by IR microscopy detection show in combination with grand canonical Monte Carlo simulations that this moderate ethene selectivity of the ZIF-8 membrane can be explained by the interplay of a preferential ethane adsorption selectivity competing with a preferential ethene diffusion selectivity. This means, that ethane adsorbs stronger than ethene, but ethene diffuses faster and overcompensates the adsorption preference of ethane, resulting in a membrane permeation selectivity for ethene

Metal-organic framework ZIF-8 nanocomposite membrane for efficient recovery of furfural via pervaporation and vapor permeation

Furfural (2-furancarboxaldehyde) has been regarded as an important platform molecule in biorefinery and has gain a wide range of applications. With the state-of-the-art biorefinery technique, the concentration of furfural in the product water stream is generally low (around 3 wt%). It is therefore highly desirable to develop efficient alternative recovery technologies that can lower the recovery costs, thus improving the economics of furfural production. In this work, a homogeneous ZIF-8-silicone rubber nanocomposite membrane with high particle loading was successfully fabricated on a hierarchically ordered stainless-steel-mesh (HOSSM) employing a novel "Plugging-Filling" method. The membrane exhibits the highest pervaporation separation index (separation factor 53.3 and total flux 0.90 kg m(-2) h(-1)) reported so far and excellent stability in a test of more than 120 h at 80 degrees C for recovery of furfural (1.0 wt%) from water. This very high performance should be attributed to the exceptional adsorption selectivity and capacity of ZIF-8 toward furfural molecules and the effects of space restriction and physical cross-linking of the HOSSM. This is a good demonstration of the potential of MOF membranes for separating biomass derived compounds in biorefinery processes. (C) 2012 Elsevier B.V. All rights reserved

Formate modulated solvothermal synthesis of ZIF-8 investigated using time-resolved in situ X-ray diffraction and scanning electron microscopy

Time-resolved investigations using in situ energy-dispersive X-ray diffraction in tandem with ex situscanning electron microscopy revealed that solvothermal crystallisation of ZIF-8 in methanol solvent and in the presence of sodium formate as a simple monodentate ligand (modulator) is a rapid process yielding big, high-quality single crystals in short time (<4 h). Kinetic analysis of crystallisation curves was performed by applying the Avrami–Erofe'ev and Gualtieri models. The analyses revealed that the weakly basic formate modulator acts as a base in deprotonation equilibria (deprotonation of the bridging 2-methylimidazole ligand) rather than as a competitive ligand in coordination equilibria at the metal (Zn2+) centres. This is in contrast to the coordination modulation function of formate in ZIF-8 synthesis at room temperature. Crystal shape evolves with time in the presence of formate from cubes with truncated edges to rhombic dodecahedra. The latter shape represents most likely the stable equilibrium morphology of ZIF-8

Blood transfusion determines postoperative morbidity in pediatric cardiac surgery applying a comprehensive blood-sparing approach

OBJECTIVE: Recently we suggested a comprehensive blood-sparing approach in pediatric cardiac surgery that resulted in no transfusion in 71 infants (25%), postoperative transfusion only in 68 (24%), and intraoperative transfusion in 149 (52%). We analyzed the effects of transfusion on postoperative morbidity and mortality in the same cohort of patients. METHODS: The effect of transfusion on the length of mechanical ventilation and intensive care unit stay was assessed using Kaplan-Meier curves. To assess whether transfusion independently determined the length of mechanical ventilation and length of intensive care unit stay, a multivariate model was applied. Additionally, in the subgroup of transfused infants, the effect of the applied volume of packed red blood cells was assessed. RESULTS: The median length of mechanical ventilation was 11 hours (interquartile range, 9-18 hours), 33 hours (interquartile range, 18-80 hours), and 93 hours (interquartile range, 34-161 hours) in the no transfusion, postoperative transfusion only, and intraoperative transfusion groups, respectively (P < .00001). The corresponding median lengths of intensive care unit stay were 1 day (interquartile range, 1-2 days), 3.5 days (interquartile range, 2-5 days), and 8 days (interquartile range, 3-9 days; P < .00001). The multivariate hazard ratio for early extubation was 0.24 (95% confidence interval, 0.16-0.35) and 0.37 (95% confidence interval, 0.25-0.55) for the intraoperative transfusion and postoperative transfusion only groups, respectively (P < .00001). In addition, the cardiopulmonary time, body weight, need for reoperation, and hemoglobin during cardiopulmonary bypass affected the length of mechanical ventilation. Similar results were obtained for the length of intensive care unit stay. In the subgroup of transfused infants, the volume of packed red blood cells also independently affected both the length of mechanical ventilation and the length of intensive care unit stay. CONCLUSIONS: The incidence and volume of blood transfusion markedly affects postoperative morbidity in pediatric cardiac surgery. These results, although obtained by retrospective analysis, might stimulate attending physicians to establish stringent blood-sparing approaches in their institutions