Room Temperature Reduction of Nitrogen Oxide on Iron Metal-Organic Frameworks.

Nitrogen oxides represent one of the main threats for the environment. Despite decades of intensive research efforts, a sustainable solution for NOx removal under environmental conditions is still undefined. Using theoretical modelling, material design, state-of-the-art investigation methods and mimicking enzymes, it is found that selected porous hybrid iron(II/III) based MOF material are able to decompose NOx, at room temperature, in the presence of water and oxygen, into N2 and O2 and without reducing agents. This paves the way to the development of new highly sustainable heterogeneous catalysts to improve air quality.

Formation of Polyaniline-MOF Nanocomposites Using Nano-Sized Fe(III)-MOF for Humidity Sensing Application.

Polyaniline (PA)-MOF nanocomposites have been successfully synthesized through an in-situ chemical oxidative polymerization of aniline in the presence of nano-sized iron trimestate (named as MIL-100(Fe)) particles, which was prepared by a microwave-irradiation method. Water sorption and humidity sensing results clearly showed that water sorption rate and humidity sensitivity are dramatically enhanced by the composites using nano-sized MIL-100(Fe) as compared with that using micrometer-sized MIL-100(Fe) particles.

Fabrication of the microchannel by metal-organic framework, copper benzenetricarboxylate.

We successfully fabricated the metal-organic framework (MOF), copper benzenetricarboxylate on a microchannel system, which was able to solve the problems created by increased heat dissipation in small electronic equipment. The microchannel system was designed to make an entrance part that can control the reaction temperature, which was predicted through a heat transfer analysis and the finite element method with COMSOL Multiphysics. Synthetic conditions, synthesis time, temperature and microchannel size were systematically tuned for the selective fabrication of copper benzenetricarboxylate on a microchannel surface. Scanning electron microscope (SEM) images, selected area electron diffraction (SAED) pattern and Fourier transform infrared (FT-IR) data clearly demonstrated that copper benzenetricarboxylate was strongly adhered to the bottom surfaces of the microchannels. Moreover, the synthesis of MOF in the microchannel system provided a much faster growth rate and better crystallinity compared to a conventional synthesis method.

Phase selectivity in the synthesis of cobalt(II) 4-cyclohexene-1,2-dicarboxylates under microwave irradiation.

Different phases in hybrid complexes of Co(II) with cis-4-cyclohexene-1-2-dicarboxylicacid (C6H8-1,2-CO2H=Cy-H2) have been generated depending on the reaction conditions. By microwave-irradiation of the same reaction mixtures at different temperatures we have obtained two new phases Co(C8H8O4) x H2O and [Co2(OH)2.8(Cy-H)1.2]. These phases have been established by XRD, UV-DRS, IR and thermo-gravimetric studies as well as by comparison with the reported phases. In these phases the Cy is found in a cis conformation. It has been seen that microwave synthesis proves to be a rapid and clean method of obtaining new high temperature phases in high purity which are obtained, in an impure state after a long time of hydrothermal synthesis.

Discovering the active sites for C3 separation in MIL-100(Fe) by using operando IR spectroscopy.

A reducible MIL-100(Fe) metal-organic framework (MOF) was investigated for the separation of a propane/propene mixture. An operando methodology was applied (for the first time in the case of a MOF) in order to shed light on the separation mechanism. Breakthrough curves were obtained as in traditional separation column experiments, but monitoring the material surface online, thus providing evidences on the adsorption sites. The qualitative and quantitative analyses of Fe(II) and, to some extent, Fe(III) sites were possible, upon different activation protocols. Moreover, it was possible to identify the nature and the role of the active sites in the separation process by selective poisoning of one family of sites: it was clearly evidenced that the unsaturated Fe(II) sites are mainly responsible for the separation effect of the propane/propene mixture, thanks to their affinity for the unsaturated bonds, such as the C=C entities in propene. The activity of the highly concentrated Fe(III) sites was also highlighted.

Intracrystalline diffusion in metal organic framework during heterogeneous catalysis: influence of particle size on the activity of MIL-100 (Fe) for oxidation reactions.

Three MIL-100 (Fe) samples differing in average crystal size (from 60-70 to >400 nm) have been synthesized by microwave heating using three HF/Fe(3+) ratios. Oxidation of diphenylmethane with tert-butylhydroperoxide (TBHP) and thiophenol with oxygen are catalyzed by three MIL-100 (Fe) samples with similar reaction rates regardless of its average particle size. In contrast, the activity of the three MIL-100 (Fe) samples for the oxidation of bulky triphenylmethane by TBHP largely depends on the average crystal size of the sample: the smaller the average particle size, the larger the initial reaction rate of triphenylmethane oxidation. These results show that diffusion limitation takes place on MOF catalysis depending on the substrate size and provides indirect evidence that these reactions take place inside the intracrystalline space of the porous catalysts.

Synthesis and humidity sensing characteristics of polyaniline/BaTiO3 composites.

An attempt has been made towards the synthesis of polyaniline/BaTiO3 (PANI-BTO) composite with an objective to examine the possibility of using this composite for humidity sensing. In this work, PANI-BTO composites were synthesized by an in situ chemical oxidative polymerization of aniline in presence of BaTiO3 particles. These composites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The electrolyte pH significantly affects the synthesis of PANI-BTO composite. At lower pH, the formation of BaSO4 was observed in the composite which may be due to the leaching of Ba2+ ions from the surface of BaTiO3 particles in HCl medium. The exclusive formation of PANI-BTO composite without BaSO4 was achieved at higher pH (5.7). The PANI-BTO composites show better sensing properties than pure PANI, such as higher response factor and quicker response. The composites with 50 wt% of BaTiO3 exhibit an exponential relationship between the resistance and RH irrespective of electrolyte pH used for the synthesis.

Swift synthesis of hierarchically ordered mesocellular mesoporous silica by microwave-assisted hydrothermal method.

Hierarchically ordered mesocellular mesoporous silicas (HMMS) were swiftly synthesized using P123 and sodium silicate as a silica source within an hour by applying microwave irradiation without pore expander. The XRD, TEM and BET studies demonstrated that materials as-synthesized and calcined have the hierarchically ordered mesocellular structure with two different sizes about 10 nm and 30 nm pores having a minimized micropore volume compared with conventional hydrothermal method. Moreover, the HMMS sample prepared by microwave-assisted hydrothermal method had higher surface area than that of conventional hydrothermal method. The variation of the pore size and morphology of mesocellular structure varied with the aging time.

Synthesis and catalytic properties of MIL-100(Fe), an iron(III) carboxylate with large pores.

The large-pore iron(III) carboxylate MIL-100(Fe) with a zeotype architecture has been isolated under hydrothermal conditions, its structure solved from synchrotron X-ray powder diffraction data, while Friedel-Crafts benzylation catalytic tests indicate a high activity and selectivity for MIL-100(Fe).