Search

Objective: Stem cells in glioblastoma (GBM) are considered to be a main contributor for the high levels of therapy resistance of the disease. The identification of metabolic dependencies of those GBM stem cells (GSCs), such as glutaminase 1 activity, opens a new area for future management of neuro oncology[for full text, please go to the a.m. URL], 72. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Polnischen Gesellschaft für Neurochirurgie

Herein, we report the first synthesis of covalent triazine-based frameworks (CTFs) based on a hexanitrile monomer, namely the novel pseudo-octahedral hexanitrile 1,4-bis(tris(4′-cyano-phenyl)methyl)benzene 1 using both ionothermal reaction conditions with ZnCl2 at 400 °C and the milder reaction conditions with the strong Brønsted acid trifluoromethanesulfonic acid (TFMS) at room temperature. Additionally, the hexanitrile was combined with different di-, tri-, and tetranitriles as a second linker based on recent work of mixed-linker CTFs, which showed enhanced carbon dioxide captures. The obtained framework structures were characterized via infrared (IR) spectroscopy, elemental analysis, scanning electron microscopy (SEM), and gas sorption measurements. Nitrogen adsorption measurements were performed at 77 K to determine the Brunauer-Emmett-Teller (BET) surface areas range from 493 m2/g to 1728 m2/g (p/p0 = 0.01–0.05). As expected, the framework CTF-hex6 synthesized from 1 with ZnCl2 possesses the highest surface area for nitrogen adsorption. On the other hand, the mixed framework structure CTF-hex4 formed from the hexanitrile 1 and 1,3,5 tricyanobenzene (4) shows the highest uptake of carbon dioxide and methane of 76.4 cm3/g and 26.6 cm3/g, respectively, at 273 K.

Bottom-up and top-down approaches are described for the challenging synthesis of Fe/Al nanoparticles (NPs) in ionic liquids (ILs) under mild conditions. The crystalline phase and morphology of the metal nanoparticles synthesized in three different ionic liquids were identified by powder X-ray diffractometry (PXRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), selected-area electron diffraction (SAED) and fast Fourier transform (FFT) of high-resolution TEM images. Characterization was completed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) for the analysis of the element composition of the whole sample consisting of the NPs and the amorphous background. The bottom-up approaches resulted in crystalline FeAl NPs on an amorphous background. The top-down approach revealed small NPs and could be identified as Fe4Al13 NPs which in the IL [OPy][NTf2] yield two absorption bands in the green-blue to green spectral region at 475 and 520 nm which give rise to a complementary red color, akin to appropriate Au NPs. © 2020 The Royal Society of Chemistry.

Porous composite materials are potential candidates for water-based adsorptive heat transformation (AHT) applications. Here, a solid adsorbent LiCl@UiO-66 as a 'composite salt inside porous matrix' (CSPM) has been prepared by incorporating hygroscopic lithium chloride into a microporous metal-organic framework (MOF) UiO-66 as a host matrix through the wet impregnation method. In our wet impregnation we did not let the excess salt solution dry to prevent salt precipitation on the matrix surface. This yielded a true salt@MOF composite with no deliquescence of LiCl and strongly enhanced the water adsorption capacity of UiO-66 through the salt content. At p/p0 = 0.1 the water vapor sorption isotherms show a hydration state of LiCl inside the MOF of LiCl·2-4H2O which is much higher than for neat LiCl with 0.5H2O, due to the dispersion of a small particle size inside the matrix. LiCl@UiO-66 with a 30 wt% LiCl content (LiCl@UiO-66_30) has a 3 to 8 times higher water uptake over neat UiO-66 (depending on relative pressure) and could reach a volumetric and gravimetric water uptake of over 2.15 g g−1 at p/p0 = 0.9, which outperforms the so far known UiO-66-based composites. Cycling tests confirmed the hydrothermal stability of the LiCl@UiO-66 composites. Kinetic evaluation of the gravimetric water uptake (at 90% relative humidity) over time yielded rate coefficients up to 2.0(1) × 10−4 s−1 which is slower than that in neat UiO-66 (6.7(6) × 10−4 s−1) but faster than that for salt@silica gel composites. The coefficient of performance for the heat pumping mode (at Tdes/Tads/Tevap set to 90/40/10 °C) of 1.64 for LiCl@UiO-66_30 exceeds those of other MOFs, salt@MOF or salt@silica gel composites. For thermal battery applications the heat storage capacity (CHS) for LiCl@UiO-66_30 is 900 kJ kg−1 (=0.25 kW h kg−1), which can reach the Department of Energy (DOE) value of 2.5 kW h/35 kg with just 10 kg of material and outperforms CaCl2@UiO-66_38 with a CHS value of 367 kJ kg−1.

Cyclic physical adsorption and desorption processes on porous materials can be used for the conversion of heat in heat transformation processes, which is the working principle in adsorption heat pumps (AHPs). Environmentally benign water with its high enthalpy of evaporation is the working fluid of choice in AHPs. Metal‐organic frameworks, MOFs can adsorb large amounts of water or methanol, up to their own weight. MOFs could be alternative materials to silica gels, zeolites, or aluminum phosphates for low‐temperature heat transformations in AHPs.

The recently reported Al-based metal-organic framework MIL-53(Al)-TDC (TDC = 2,5-thiophenedicarboxylate) shows desirable water sorption properties towards adsorption-driven heat transformation applications with high thermal and solvent/pH stability as well as hydrothermal stability over 40 cycles. Water vapor sorption measurements at 25, 40 and 60 °C yielded an advantageous isosteric heat of adsorption of only 2.6 kJ g−1, favoring the use of MIL-53(Al)-TDC in sorption based chilling where the released heat of adsorption corresponds to waste heat. The good cooling performance of MIL-53(Al)-TDC comes from desirable low desorption temperatures below 65 °C, with also desirable high condenser temperatures of around 40 °C and corresponding water exchange of almost 0.35 g g−1. The thereby offered working window cannot be provided by common adsorbents and renders the material an ideal candidate for adsorption cooling applications.

Metal-organic frameworks represent a class of microporous adsorbents with high application potential for adsorption heat transformation. Here, we present a functional, full-scale heat exchanger coated with the microporous aluminum fumarate MOF Basolite A520 using a polysiloxane-based binding agent. The function of the heat exchanger was evaluated resulting in a gross cooling power of 2900 W (at the beginning of the adsorption cycle) or, respectively an average cooling power of 690 W (up to a limit of 90% equilibrium loading in 7 min) under the working conditions of a realistic adsorption chiller of 90 °C - 30 °C - 18 °C (temperature level of heat source, heat rejection/condenser, and evaporator).

Dihalogenometal(II) complexes with bidentate phosphane ligands of the general type [M{Ph2P(CH2)nPPh2} X2] with n = 2 to 5, X = Cl or Br and M = Co, Ni or Pd have been utilized as catalysts for the vinyl/addition polymerization of norbornene. These complexes can be activated with the Lewis-acids methylalumoxane (MAO) or tris(pentafluorophenyl)borane, B(C6F5)3 in combination with triethylaluminium (AlEt3). The nickel(II) and palladium(II) complexes show very high polymerization activities up to 107 gpolymer molmetal-1 h-1. Yet, the complexes Pd(dppe)Cl2 (5, 1.9 × 107 gpolymer molPd-1 h-1) and Pd(dppp)Cl2 (6, 3.0 × 103 gpolymer molPd-1 h-1) demonstrated that small changes in the ligand structure could have great effects on the polymerization activity [dppe = 1,2-bis(diphenylphosphino)ethane, Ph2P(CH2)2PPh2; dppp = 1,3-bis(diphenylphosphino)propane, Ph2P(CH2)3PPh2]. The activation process of the pre-catalysts 5 and 6 in combination with B(C6 F5)3/AlEt3 was followed by multinuclear (1H, 19F, and 31P) NMR investigations and by reaction with B(C6 F5)3 and Ag[closo-1-CB11H12]. The reaction of B(C6F5)3 and AlEt3 leads to an aryl/alkyl group exchange resulting in the formation of AlEt3-n(C6F5)n and B(C6F5)3-nEtn with Al(C6F5)3 and BEt3 as main products for an about equimolar ratio. AlEt3-n(C6F5)n will then react with the pre-catalysts and abstract the chloride atoms to form [M{Ph2 P(CH2)nPPh2}]2+ as the active species for the polymerization. The higher polymerization activity of 5/B(C6F5)3/AlEt3 compared to 6/B(C6F5)3/AlEt3 can be explained by a ligand redistribution reaction of unstable [PdII (dppe)]2+ to give inactive and isolable [PdII(dppe)2]2+ and highly active, "naked" Pd2+ cations together with the lower coordinating ability of the anionic adduct [Cl-Al(C6F5)3]- in comparison to [Cl-B(C6F5)3]-. The Lewis-acid Al(C6F5)3 is much more activating than B(C6F5)3. The [Pd(dppe)2]2+ cation from the ligand redistribution was isolated in the (X-ray) structurally elucidated compounds [PdII(dppe)2]-[ClB(C6 F5)3]2·4CH2Cl2 and [PdII(dppe)2][CB11 H11Cl]2·3CH2Cl2. The stable [Pd(dppp)]2+ cation from 6 could be crystallized as [PdII(dppp)(CB11H12)] [CB11H12] (CB11H12 = mono-anionic carborane [closo-1-CB11H12]-).

Micro- to mesoporous iron(III) trimesate MIL-100(Fe) is a MOF of high interest for numerous applications. With regard to large-scale synthesis, e.g., by continuous flow or the in situ deposition of coatings, a replacement for the conventional, hydrothermal low-yield fluoride-containing synthesis is desirable. In this contribution, we present a method to synthesize crystalline fluoride-free MIL-100(Fe) from iron(III) nitrate and trimesic acid in zeotropic DMSO/water solution at normal ambient pressure involving a DMSO nitrate redox pathway. Yields of 72%, surface areas of S-BET = 1791 m(2) g(-1) and pore volumes of V-pore = 0.82 cm(3) g(-1) were achieved.

Aluminium isophthalate CAU-10-H [Al(OH)(benzene-1,3-dicarboxylate)]·nH2O exhibits water adsorption characteristics which make it a promising adsorbent for application in heat-exchange processes. Herein we prepared a stable coating of this MOF and evaluated its long-term stability under closed-cycle conditions for 10000 water adsorption and desorption cycles, which are typical lifetimes for adsorption heat storage (AHS) applications. No degradation of the adsorption capacity could be observed which makes CAU-10-H the most stable MOF under these humid cycling conditions reported until now. Moreover, thermophysical properties like thermal conductivity and heat of adsorption were directly measured. In order to identify the structural features associated with the adsorption behaviour, the structural differences between the dry and the water loaded CAU-10-H were studied by Rietveld refinements and second harmonic generation (SHG) microscopy.

This paper presents experimental and theoretical investigations of adsorption characteristics of ethanol onto metal organic framework namely MIL-101Cr. Adsorption isotherms and kinetics of the studied pair have been measured gravimetrically using a magnetic suspension adsorption measurement unit and volumetrically employing a Quantachrome Autosorb iQ MP machine. The present experiments have been conducted within relative pressures between 0.1 and 0.9 and adsorption temperatures ranging from 30 to 70 degrees C, which are suitable for adsorption cooling applications. Adsorption isotherm data exhibit that 1 kg of MIL-101Cr can adsorb as high as 1.1 kg of ethanol at adsorption temperature of 30 degrees C, and the Toth equation has been used to fit the experimentally measured data. As of the experimentally measured adsorption uptake rate data, the Fickian diffusion model is found to be suitable. These data are essential for designing a new generation of adsorption chiller.

MIL-101(Cr), one of the most important prototypical MOFs, is well investigated and widely used in many scientific fields. With regard to MOF synthesis in general, the addition of a modifier is commonly used to improve the properties of the products. The effect of inorganic (mineral) and organic acid modifiers was thoroughly investigated in the synthesis of MIL-101(Cr) and HNO3 could increase the yield to over 80% of a product with average S-BET > 3200 m(2) g(-1) in repeated experiments (from an average of 50% in most published syntheses) in small-scale laboratory synthesis. The large-scale synthesis could use the finding of HNO3 addition and produce MIL-101(Cr) in >100 g quantities with yields near 70% and BET-surface areas near 4000 m(2) g(-1). The addition of acetic acid (CH3COOH) together with seeding could decrease the reaction temperature, the lowest being 160 degrees C (from typically 220 degrees C in published procedures), with still relatively good yield and BET surface area of the product. The use of other strong inorganic or weak carboxylic acids as modulators typically caused a decrease in yield and porosity.

The hydrothermal stability of aluminium hydroxide isophthalate MOF CAU-10-H was proven{,} under humid multi-cycling conditions. Detailed in situ thermogravimetric measurements and in situ powder X-ray diffraction analysis during water ad-/desorption were used. A reversible structural change during adsorption was detected and thereby exemplified the robustness of breathing-like MOFs over 700 water vapour ad/desorption cycles. In combination with high water adsorption capacity{,} hydrophilic CAU-10-H is the first breathing-like MOF with a structural change which is a promising candidate for the use in heat transformation processes.

Microporous materials with high water uptake capacity are gaining attention for low temperature heat transformation applications such as thermally driven adsorption chillers (TDCs) or adsorption heat pumps (AHPs). TDCs or AHPs are alternatives to traditional air conditioners or heat pumps operating on electricity or fossil fuels. By using solar or waste heat as the driving energy, TDCs or AHPs can minimize primary energy consumption. TDCs and AHPs are based on the evaporation and consecutive adsorption of coolant liquids, preferably water, under specific conditions. Their ranges of application, as well as their efficiencies, power densities and total costs, are substantially influenced by the microporosity and hydrophilicity of the employed sorption materials. Here, we briefly summarize current investigations, developments and possibilities of metal-organic frameworks (MOFs) compared to classical materials. With their high water uptake, MOFs surpass those materials, while, at the same time, the variability of the building blocks allows for tuning of the microporosity and hydrophobic/hydrophilic design, depending on the specific application.

Sorption-based heat transformation and storage appliances are very promising for utilizing solar heat and waste heat in cooling or heating applications. The economic and ecological efficiency of sorption-based heat transformation depends on the availability of suitable hydrophilic and hydrothermally stable sorption materials. We investigated the feasibility of using the metal-organic frameworks UiO-66(Zr), UiO-67(Zr), H2N-UiO-66(Zr) and H2N-MIL-125(Ti) as sorption materials in heat transformations by means of volumetric water adsorption measurements, determination of the heat of adsorption and a 40-cycle ad/desorption stress test. The amino-modified compounds H2N-UiO-66 and H2N-MIL-125 feature high heat of adsorption (89.5 and 56.0 kJ mol−1, respectively) and a very promising H2O adsorption isotherm due to their enhanced hydrophilicity. For H2N-MIL-125 the very steep rise of the H2O adsorption isotherm in the 0.1 < p/p0 < 0.2 region is especially beneficial for the intended heat pump application.

Item does not contain fulltext

For many possible applications of metal-organic frameworks, a coating onto a metallic support capable of both superior heat and mass transfer is required. A heated substrate in contact with a chilled solution of metal salt and linker reproducibly yields polycrystalline, highly stable, thermally conductive MOF coatings at a growth rate of 50 mu m h(-1), illustrated by the formation of Cu-3(btc)(2) as an example.

The adsorption/desorption of up to 0.75 g of water vapour per g of the porous MOFs 3D-{M 3O(X)(H 2O) 2[btc] 2·nH 2O}, MIL-100 (M = Al, Fe; X = OH, F, btc = benzene-1,3,5-tricarboxylate, trimesate), occurs at small relative pressures of p/p 0 < 0.4 and a comparatively small hysteresis. Together with very good cycle stability, these properties render both MIL-100(Al and Fe) very suitable candidates for thermally driven heat pumps or adsorption chillers.