Suchergebnisse

In the past six years we have been intensively collaborating with the Chemistry Department of Addis Ababa University as well as Haramaya University to bust scientific knowledge related to zeolites and zeolite applications. Initially, we teamed up with geologists and government actors in the mining sectors; as a result we got access to natural zeolites from the north of the country, as well as other industrial minerals such as kaolin. In parallel we developed research activities in the use of zeolites as adsorbents and in catalytic processes related to environmental applications of necessity in Ethiopia. In the first part of this paper I will describe two examples of adsorption processes using mineral resources: one is a natural stilbite used to develop an adsorbent to remove fluoride from drinking waters; and the second one uses virgin kaolin to prepare a synthetic zeolite 4A that we used to remove chromium from tannery wastewaters. Finally, two catalytic examples will be described: in the first one we tackled the photocatalytic degradation of dyes from textile industries using Ti-modified natural and synthetic zeolites, and in the second one we used modified mordenites, both natural and synthetic, for the conversion of glucose into 5-HMF. ; ID is grateful to CSIC for her research leave at AAU and HU. The Spanish Research Council CSIC I-COOP+-2014 (COOPB20082) is acknowledged for funding. This work has been (partially) funded by the Spanish State Research Agency (AEI) and the European Regional Development Fund (FEDER) through the Project MAT2016-77496-R (AEI/FEDER, UE) and Project MAT2015-65767-P. Special thanks go to the members of the Molecular Sieves Group at ICP-CSIC. ; Peer reviewed

Special Issue: Advanced Microscopy and Spectroscopy for Catalysis . ; Metal-organic frameworks (MOFs) are a family of porous solids combining organic and inorganic moieties with tunable porosity. Their structural parameters have converted MOFs into suitable compounds for gas storage or drug delivery. However, despite the excellent crystallinity they tend to exhibit their analysis through transmission electron microscopy is extraordinarily complicated owing to the high instability under the electron beam irradiation. In here, high-resolution Cs-corrected STEM imaging was used for the observation of the building units of MIL-100(Fe), and special attention was paid to the electron beam current. In addition, MIL-100(Fe) was reacted with AgNO3 through a solid-state reaction technique, which resulted into the formation of metal nanoparticles on the surface. The incorporation of Ag into the porous network has been also investigated. ; AM acknowledges the Government of Aragon and the European Social Fund under the project grant number E/26 "Construyendo Europa desde Aragón" 2014–2020. This work has been partially financed by the Spanish State Research Agency (Agencia Española de Investigación, AEI) and the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER) through Project MAT2016-77496-R (AEI/FEDER, UE). ; Peer reviewed

One of the pioneering metal organic framework material, called MOF-2 and having the formula [Zn2(BDC)2], still continues awakening interest amongst the scientific community in spite of its layered character. However, the synthesis methods are either experimentally complicated or in two steps through the transformation of MOF-1. Here, we describe the preparation of a high-quality MOF-2 under more sustainable conditions, including room temperature, absence of any amine or any other pH-controller, partial substitution of the harmful organic solvent (N,N-dimethylformamide) by water, and by simply mixing linker and metal sources, the latter being zinc acetate, carefully selected as a function of their solubility in the solvent mixture. The optimum ratio of Zn(OAc)2·4H2O to terephthalic acid (H2BDC) is 1.74 and H2O to DMF is 3. MOF-2 [Zn2(BDC)2] has been characterized using powder X-ray diffraction, thermogravimetric analysis, N2 adsorption/desorption and scanning electron microscopy, all of them supporting the good quality of the material. ; NG acknowledges the financial support from the Spanish Ministry of Foreign Affairs-Spanish Agency for Cooperation and Development through the "Becas Institucionales" Program. ID acknowledges the CSIC for the research leave at Addis Ababa University. The authors acknowledge Spanish Government, MINECO (MAT2012-31127) and the Spanish Research Council CSIC (i-COOP014), for funding. The Chemistry Department, Addis Ababa University is also acknowledged for financial support. ; Peer Reviewed

© 2014 American Chemical Society ; This paper describes the preparation and characterization of nanoscaled M-MOF-74/CPO-27-M (M = Mg, Mn, Co, Ni, and Zn) materials at room temperature. Some of the so-formed crystals are the smallest ones of any metal−organic framework (MOF) material (and, to the best of our knowledge, of any microporous material) ever reported. They are at the limit of being able to diffract, particularly those forming the Co- and Ni-MOF-74 samples. Consequently, unequivocal identification as the crystalline MOF-74 phase was deduced by combining other characterization techniques rather than powder X-ray diffraction. These small crystals are unstable as isolated ones, so they form steady and robust aggregates, whose mechanical properties strongly depend on the crystal size. The particles that result from the "fusion" of nanocrystals smaller than 10 nm (more properly denoted as nanodomains) could not be disaggregated by conventional ultrasonic and graining techniques. On the contrary, agglomerates of crystals larger than 10 nm are dissociable in discrete crystals. It allows characterizing Zn-MOF-74 nanocrystals by advanced electron microscopy methods. Cs-corrected scanning transmission electron microscopy (STEM) provided, for the first time, "quasi" atomic resolution images of MOFs, which are especially unstable under electronic radiation. The magnitude of the crystal size of M-MOF-74 is tentatively associated with the solubility of the metal source. ; Funding is from Spanish Ministry (MAT-2012−31127) and European Union Seventh Framework Programme under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative-I3). ; Peer Reviewed

Siliceous ordered mesoporous materials (OMM) are gaining interest as supports for enzyme immobilization due to their uniform pore size, large surface area, tunable pore network and the introduction of organic components to mesoporous structure. We used SBA-15 type silica materials, which exhibit a regular 2D hexagonal packing of cylindrical mesopores of uniform size, for non-covalent immobilization of laccase. Synthesis conditions were adjusted in order to obtain supports with different particle shape, where those with shorter channels had higher loading capacity. Despite the similar isoelectric points of silica and laccase and the close match between the size of laccase and the pore dimensions of these SBA-15 materials, immobilization was achieved with very low leaching. Surface modification of macro-/mesoporous amorphous silica by grafting of amine moieties was proved to significantly increase the isoelectric point of this support and improve the immobilization yield. © 2014 by the authors. ; The authors thank the Spanish Government for financial support through the project MAT 2012-31127, and Ramiro Martinez (Novozymes, Spain) for his kind help with the supply of laccase. V. G. acknowledges Ministerio de Educación, Cultura y Deporte for a FPU PhD fellowship. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI) ; Peer Reviewed

The real industrial establishment of metal–organic frameworks (MOFs) requires significant advances in economic and chemical sustainability. This work describes a novel and simple method to prepare one of the most widely studied MOF materials, i.e., MIL-100(Fe), which significantly improves the sustainability of the conventional process in several aspects. This MOF material is prepared (i) at room temperature (instead of 150 °C used in the conventional method), (ii) after a few hours (instead of 6 days), (iii) in the absence of any inorganic corrosive acid (significant amounts of HF and HNO3 are used in the conventional method), and (iv) it is washed at room temperature (unlike the washing at 80 °C for 3 h). Interestingly, the only difference in the preparation method of MIL-100(Fe) compared with that of semiamorphous Fe-BTC (MOF material commercialized as Basolite F300 having the same metal and linker, and which can be also prepared under similar sustainable conditions) is to start from Fe(II) or Fe(III) sources, respectively, which opens certain versatility options in the room temperature synthesis procedures of MOF materials. The prepared samples were characterized using X-ray diffraction, thermogravimetric analysis, N2 adsorption/desorption isotherms, Cs-aberration corrected scanning transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. These two room-temperature-made Fe-BTC materials were tested in the industrially demanded photocatalytic degradation of methyl orange under both ultraviolet and solar light radiation. MIL-100(Fe) was a very active photocatalyst in comparison with its homologue. That difference was mainly attributed to the presence of larger cavities within its structure. ; A.M. acknowledges European Union Seventh Framework Programme under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative-I3). C.A.D.C. acknowledges Science without Borders - CNPq - Brazil. K.G. and I.D. also acknowledge CSIC for Development Program I-COOP-2014 COOPB20082 project number. This work has been (partially) financed by the Spanish State Research Agency (Agencia Española de Investigación, AEI) and the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER) through Project MAT2016-77496-R (AEI/FEDER, UE). ; Peer reviewed

Mixed ligand complexes of 2,2′-bipyridine and 1,10-phenanthroline with iron(III) and nickel(II) have been encapsulated into a zeolite cage by the reaction of zeolite exchanged metal ion with flexible ligands. The synthesized catalyst has been characterized by X-ray powder diffraction, scanning electron microscopy, BET surface area and pore volume analysis, FT-IR spectroscopy, thermo-gravimetric analysis and elemental analysis. Density functional theory calculations have been carried out on both neat complexes as well as metal complexes encapsulated into NaY zeolite to investigate changes in structural parameters, energies of the HOMO and LUMO, and global hardness and softness of the two metal complexes upon encapsulation into zeolite. Experimental results confirm successful formation of a mixed ligand complex of Fe(III) and Ni(II) inside the zeolite cage. Density functional theory calculations predict a higher reactivity of the zeolite encapsulated metal complexes compared to respective metal complexes. The zeolite encapsulated Fe(III) and Ni(II) complexes are found to be catalytically active toward the oxidation of 2-phenyl phenol (OPP). ; Solomon Legese Hailu sincerely thanks the Leather Industry Development Institute (LIDI), Government of Ethiopia, Addis Ababa, for full nancial support for his PhD studies under Twinning Program between Leather Industry Development Institute (LIDI), Addis Ababa University (AAU) and CSIR-Central Leather Research Institute (CLRI). ID acknowledges CSIC, Spain for the research leave at AAU. ; Peer Reviewed