Facile synthesis of an ultramicroporous MOF tubular membrane with selectivity towards CO(2)

International audienceA substituted imidazolate-based MOF (SIM-1) membrane has been crystallized in situ on a tubular asymmetric alumina support that can be exploited for gas separation through preferential adsorption

Tests for the Use of La2Mo2O9-based Oxides as Multipurpose SOFC Core Materials

International audienceThe mixed ionic-electronic conductivity under dilute hydrogen, the stability and the catalytic activity under propane:air type mixtures of a series of LAMOX oxide-ion conductors have been studied. The effect of exposure to dilute hydrogen on the conductivity of the -La2(Mo2 - yWy)O9 series at 600 °C depends on tungsten content: almost negligible for the highest (y = 1.4), it is important for La2Mo2O9 (y = 0). In propane:air, all tested LAMOX electrolytes are stable at 600-700 °C, but get reduced when water vapour is present. La2Mo2O9 is the best oxidation catalyst of the series, with an activity comparable to that of nickel.The catalytic activity of other tested LAMOX compounds is much lower, (La1.9Y0.1)Mo2O9 showing a deactivation phenomenon. These results suggest that depending on composition, La2(Mo2 - yWy)O9 compounds could be either electrolytes in single-chamber SOFC and dual-chamber micro-SOFC (y = 1.4) or anode materials in dual-chamber SOFC (low y) or oxidation catalysts in SOFCs operating with propane (y = 0)

Fabrication of an Active Electronic Device Using a Hetero-bimetallic Coordination Polymer

A nickel(II)/lead(II) coordination polymer [(NCS)Pb(H2O)LNi(NCS)]n {H2L=N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine} has been synthesized and characterized. The band gap (3.18 eV) calculated from Tauc’s plot suggests the semiconducting nature of the complex. The material has a photosensitivity of 5.76, indicating its applicability in the fabrication of photosensitive devices. The complex has been successfully applied in a technologically challenging thin-film photosensitive Schottky device

Understanding the electromagnetic interaction of metal organic framework reactants in aqueous solution at microwave frequencies

Preparation of metal organic frameworks (MOFs) via microwave heating is becoming increasingly popular due to reduced reaction times and enhanced control of MOF particle size. However, there is little understanding about the detailed interaction of the electric field portion of the wave with reactants during the synthesis of MOFs. In order to overcome this lack of fundamental understanding, information about the dielectric properties of the reactants is required. In this work the dielectric constants (ε′) and loss factors (ε′′) of benzene-1,4-dicarboxylic acid (H2BDC; also known as terephthalic acid) and a number of M(III) (M = metal) salts dissolved in deionized water were measured as a function of frequency, temperature and concentration and with varying anions and cations. Dielectric data confirm the aqueous M(III) salts to be strong microwave absorbers, particularly at 915 MHz. M(III) salts with mono-anionic ligands (for example chlorides and nitrates) exhibit higher losses than di-anionic salts (sulfates) demonstrating that the former are heated more effectively in an applied microwave field. Of the M(III) salts containing either singly- or doubly-charged anions, those containing Fe(III) have the highest loss indicating that they will heat more efficiently than other M(III) salts such as Cr(III) and Al(III). Interestingly, H2BDC exhibits little interaction with the electric field at microwave frequencies

Metal–organic frameworks in seconds via selective microwave heating

Synthesis of metal–organic framework (MOF) materials via microwave heating often involves shorter reaction times and offers enhanced control of particle size compared to conventional heating. However, there is little understanding of the interactions between electromagnetic waves and MOFs, their reactants, and intermediates, all of which are required for successful scale-up to enable production of commercially viable quantities of material. By examining the effect of average absorbed power with a constant total absorbed energy to prepare MIL-53(Al) we have defined a selective heating mechanism that affords control over MOF particle size range and morphology by altering the microwave power. This is the first time a selective mechanism has been established for the preparation of MOFs via microwave heating. This approach has been applied to the very rapid preparation of MIL-53(Al)ta (62 mg in 4.3 seconds) which represents the fastest reported synthesis of a MOF on this scale to date

One-step synthesis of 2,5-bis(chloromethyl)-1,4-dioxane from epichlorohydrin using ZIF-8, taking advantage of structural defects

We demonstrate herein the ZIF-8-only-mediated catalysis of the cyclodimerization of epichlorohydrin to 2,5-bis(chloromethyl)-1,4-dioxane in the absence of co-catalyst and solvent. The easy handling and economic aspects of ZIF-8, in addition to the one-step reaction to produce the cyclodimer, make this catalyst attractive even for industry. It has been clearly illustrated that the nature of the method used to synthesize ZIF-8 affected the yields of the cyclodimers. Specifically, the method employed to produce ZIF-8 directly influences the amount of crystal structural defects, which in turn impacts their performance as catalysts. To emphasize the role of defects, other physical properties, such as surface area and particle size, were controlled during the synthesis of the ZIF-8 catalysts. Remarkably, the amount of structural defects was quantified by temperature program desorption analysis

Growth inhibition of Colletotrichum musae using plant essential oils encapsulated in metal organic frameworks nanoporous materials

Being highly perishable, 'Cavendish' banana fruits are affected by economically important postharvest diseases, like crown rot and anthracnose, which are caused by Colletotrichum musae. Fungicide treatment is considered as an effective management strategy however, its repeated applications pose risk to consumers' health, environment, and even fungal population. The use of plant essential oils (EOs), like thymol and limonene, are extensively studied as an alternative control method due to its antimicrobial properties. In this proof-ofconcept study, thymol and limonene were encapsulated in metal organic frameworks (MOFs) nanoporous materials (ZIF-8 and UiO-66) for sustained release that shall limit fungal diseases. An optimized protocol was developed to achieve a high encapsulation efficiency of EOs in MOFs (EO@MOFs). In vitro assays using several concentrations of EO@MOFs were conducted at 14°C and under controlled atmosphere (CA) storage to determine the inhibition capacity against C. musae. Encapsulated thymol reduced the growth of C. musae better than limonene. Higher concentration of EO@MOFs favorably slowed down the growth of C. musae for 11 days at 14°C and CA storage. The data suggest that volatile plant EOs when released from MOFs have the potential to slow down the growth of C. musae and may have some utility in banana postharvest disease control

Investigation of the synthesis, activation, and isosteric heats of CO₂ adsorption of the isostructural series of metal-organic frameworks M₃(BTC)₂ (M = Cr, Fe, Ni, Cu, Mo, Ru)

The synthesis, activation, and heats of CO₂ adsorption for the known members of the M₃(BTC)₂ (HKUST-1) isostructural series (M = Cr, Fe, Ni, Zn, Ni, Cu, Mo) were investigated to gain insight into the impact of CO₂–metal interactions for CO₂ storage/separation applications. With the use of modified syntheses and activation procedures, improved BET surface areas were obtained for M = Ni, Mo, and Ru. The zero-coverage isosteric heats of CO₂ adsorption were measured for the Cu, Cr, Ni, Mo, and Ru analogues and gave values consistent with those reported for MOFs containing coordinatively unsaturated metal sites, but lower than for amine functionalized materials. Notably, the Ni and Ru congeners exhibited the highest CO₂ affinities in the studied series. These behaviors were attributed to the presence of residual guest molecules in the case of Ni₃(BTC)₂(Me₂NH)₂(H₂O) and the increased charge of the dimetal secondary building unit in [Ru₃(BTC)₂][BTC].Massachusetts Institute of Technology. Energy Initiative (Seed Fund

Hollow Y zeolite single crystals: synthesis, characterization and activity in the hydroisomerization of n-hexadecane

International audienceHollow Y zeolite single crystals have been obtained from a conventional NaY zeolite following a three-step process involving a severe dealumination of the zeolite with silicon tetrachloride (step #1), followed by an acid washing under mild conditions (step #2) and finally a selective dissolution of the crystals core in the presence of protective Al species (step #3). Crystals are characterized by the presence of a regular internal cavity with 0.1–0.2 nm thick microporous walls. They contain a relatively low framework Al content but significant amounts of extraframework Al oxide species mainly located on the external surface of the crystals. Hollow crystals have been mixed with a Pt-supported alumina binder and used as catalysts in the hydroisomerization of n-hexadecane. Compared to the corresponding bulk crystals obtained after step #2, their higher activity has been attributed to a better efficiency, directly resulting from the presence of the cavity