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Air pollution is an epochal concern, particularly in urban areas, and is linked to combustion processes 1 . The emission of nitrogen oxides (NOx) constitutes a critical environmental problem, and it can affect severely human health2,3,4 . At ambient temperature and pressure NOx decomposition is thermodynamically favoured; however, this process is kinetically inhibited, owing to a high activation energy5,6 . To date, no reported catalysts have had the required properties to lower the activation energy of this process without the help of coreacting agents and high temperatures7,8,9 . Here, we show that NO conversion to molecular nitrogen can be achieved at room temperature in the presence of O2 and H2O vapour, and in the absence of any further reducing agent, using iron-based Metal-Organic Frameworks (MOFs). Further, we demonstrate that MOFs work similarly to enzymes, but are stable in environments unfriendly to living matter. These findings open large perspectives on the solution of stringent problems in chemistry, such as the removal of pollutants or the activation of highly stable molecules.

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.

Air pollution is an epochal concern, particularly in urban areas, and is linked to combustion processes 1 . The emission of nitrogen oxides (NOx) constitutes a critical environmental problem, and it can affect severely human health2,3,4 . At ambient temperature and pressure NOx decomposition is thermodynamically favoured; however, this process is kinetically inhibited, owing to a high activation energy5,6 . To date, no reported catalysts have had the required properties to lower the activation energy of this process without the help of coreacting agents and high temperatures7,8,9 . Here, we show that NO conversion to molecular nitrogen can be achieved at room temperature in the presence of O2 and H2O vapour, and in the absence of any further reducing agent, using iron-based Metal-Organic Frameworks (MOFs). Further, we demonstrate that MOFs work similarly to enzymes, but are stable in environments unfriendly to living matter. These findings open large perspectives on the solution of stringent problems in chemistry, such as the removal of pollutants or the activation of highly stable molecules.

Nowadays, MXenes have attracted significant attention owing to their extraordinary chemical and physical properties. However, it remains challenge to keep their outstanding properties in polymeric composites. Herein, by mimicking nacre with their unique layered brick-and-mortar microstructures, MXene-based nanocomposite films are developed with biocompatible polymer, xanthan. The free-standing nanocomposite films exhibit high electrical conductivity with high tensile strength (11,530 ± 176 S m−1 and 116.48 ± 6.43 MPa for the film with 67 wt% of MXene). Equally importantly, failure strain and toughness of the film with 50 wt% of MXene are dramatically increased to 6.4 and 12.7 times greater than those of neat MXene film. The substantially improved mechanical properties and high electrical conductivity of the nanocomposite films arise from the synergistic by marrying bioinspired layered brick-and-mortar structures with extraordinary material properties of MXene and the best feature of xanthan. The highly electrically conductive and mechanically robust MXene-xanthan composite films were further investigated for electromagnetic interference (EMI) shielding and Joule heating capabilities. It was demonstrated that the nanocomposite films can exhibit the exceptionally high absolute shielding effectiveness (SSE/t = 24,464.8 and 14,490.1 dB cm2 g−1 respectively for the films with 80 wt% and 67 wt% of MXene) and also uniform temperature distribution with high energy transduction efficiency and high thermal stability for Joule heating performance. Therefore, the nacre-inspired MXene-xanthan nanocomposite films can show the great promise for the use in a wide range of engineering applications such as electronics or biomedical devices. This is particularly true when it requires multiple functions including EMI shielding, thermal management, and mechanical robustness.

The effect of purification condition of a chromium terephthalate MIL-101 on gas storage (H2, CO2, and C2H2) and C2 hydrocarbon separations was investigated for MIL-101a, MIL-101b, and MIL-101c, which were obtained by three-step sequential purification using hot water/ethanol and aqueous NH4F solution treatments. MIL-101c was the best in terms of gas storage capacities among the three samples possibly due to the removal of free and coordinated terephthalic acids. Remarkably, MIL-101c exhibits among the highest total hydrogen uptake at 50 bar and 77 K (9.9 wt%) and shows considerably large deliverable capacity between 1.5 and 50 bar (7.6 wt%). Moreover, MIL-101c shows among the highest C2H2 storage capacity (6.4 mmol g−1) and deliverable capacity (4.3 mmol g−1) at 1 bar and 313 K. For C2H2/C2H6, C2H2/C2H4, and C2H4/C2H6 separations, MIL-101c exhibits higher adsorption capacities, working capacities and adsorption figure of merit (AFM) values while MIL-101b shows higher selectivities and sorbent selection parameters. These results clearly show that a proper purification of MIL-101 is important for gas storage and gas separations.

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.

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.

International audience; The adsorption of n-hexane−benzene mixture onto a chromium terephtalate-based porous material (MIL-101(Cr)) has been studied experimentally and theoretically. The adsorption isotherms of the single components show that MIL-101(Cr) has a better affinity for benzene than for n-hexane. This is in good agreement with the enthalpies of adsorption determined at low coverage. Values of −68 kJ*mol−1 and −61 kJ*mol−1 were found for benzene and n-hexane, respectively. These are consistent with the simulated enthalpies of adsorption and also with the benzene/n-hexane selectivities which range between 2 and 3 depending on the equilibrium pressure. The saturation plateau obtained with nhexane is 30% lower than that obtained with the adsorption of benzene onto MIL-101(Cr). In the case of the mixture of n-hexane−benzene, the saturation plateau is located between those obtained after adsorption of the single components. This is an indication that the coadsorption of n-hexane and benzene does not occur at the expense of one component of the mixture. However, the kinetics of adsorption of the mixture shows that benzene is adsorbed preferentially at low coverage. This is consistent with the chromatographic separation of n-hexane−benzene mixture by MIL-101(Cr).

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.

The hierarchically mesoporous iron(III) trimesate MIL-100(Fe) with a zeolite-MTN topology is known as an advanced functional material that is biocompatible. In this work, the large scale synthesis of MIL-100(Fe) has been achieved by hydrothermal reactions using suitable conditions without HF for the large scale synthesis. Although such conditions are narrow, the concurrent change of iron precursor and increase in the concentration of reaction mixture give rise to a synergetic effect leading to an increase in the crystallinity of F-free MIL-100(Fe). This method, combined with two purification steps (solvent extraction and chemical treatment with NH 4 F) leads to a highly porous F-free material obtained throughout a very high space–time-yield (>1700 kg/m 3 day). Possible formation mechanisms of MIL-100(Fe) under hydrothermal conditions have been proposed in terms of four steps such as hydrolysis, deprotonation, self-assembly, and polycondensation. The resulting material exhibits similar physicochemical properties to those of the one prepared in the presence of HF, except for a slight difference in sorption capacities of gases and liquid vapors corresponding to the difference of pore volume. Regardless of the use of HF, the purified MIL-100(Fe) possesses very high uptakes for both non-polar toluene and polar ethanol probe molecules due to the respective interactions with hydrophilic and hydrophobic sites in the framework. Finally, hydrophobicity measurements confirm that the dehydrated MIL-100(Fe) is more hydrophobic than conventional zeolite beta (SiO 2 /Al 2 O 3 = 25) and commercial iron trimesate (Basolite F300) from BASF SE.

A metal-organic framework HKUST-1 or Cu 3 (BTC) 2 was synthesized in mesopores of a COOH functionalized mesostructured cellular silica foam (MCF(M)-COOH), resulting in a hydrophobic nanocomposite. The Cu 3 (BTC) 2 formed in the MCF(M)-COOH has been prepared by a microwave method with sequential incorporation of copper nitrate and 1,3,5-benzenetricarboxylic acid in a water/ethanol mixture containing the MCF(M)-COOH. The nanocomposite was characterized by XRD, BET, FT-IR, TEM and solid state 13 C NMR. The nanocomposite had a higher hydrophobic property than pure Cu 3 (BTC) 2 and MCF(M)-COOH as a result of their hybridization. Moreover, the formation of the nanocomposite increased the sorption rate of cyclohexane vapor as compared with those of pure Cu 3 (BTC) 2 and MCF(M)-COOH due to the increased hydrophobicity.

In this work an iron MOF, MIL-100(Fe) is proposed as a plausible adsorbent to carry out C3/C4 separation by adsorption. The adsorption equilibrium of pure propane, propylene and isobutane over MIL-100(Fe) was studied by means of a magnetic suspension balance in a wide range of temperature and pressure (323–423 K and 0–500 kPa). Propane and propylene present nearly linear isotherms at high temperature, while isobutane present steeper isotherms at low pressures, showing higher adsorption capacity than that of propane and propylene in most of the studied range. Multicomponent fixed-bed adsorption experiments confirmed the preferential adsorption of isobutane over propane and propylene, with an adsorption separation factor of 3. A non-isothermal, non-adiabatic, bidisperse mass transfer model that describes satisfactorily the single and multicomponent breakthrough experiments is proposed.

Catalytic behavior of metal–organic-frameworks (MOFs) Cu 3 (BTC) 2 , MIL-100(Fe) and MIL-100(Cr) was investigated in p -xylene acylation with benzoyl chloride and compared with the behavior of large pore zeolites Beta and USY. It has been clearly shown that MIL-100(Fe) exhibit much higher conversion of benzoyl chloride with excellent selectivity in p -xylene acylation. The performance of MIL-100(Fe) catalyst was favorable with those of other conventional heterogeneous catalysts like zeolites. Conversion of benzoyl chloride equal to 100% was achieved over MIL-100(Fe) with 20–30 min under optimized reaction conditions. It is assumed that unsaturated Lewis acid sites associated with the presence of Fe exhibit optimum acid strength for catalyzing this acylation reaction.

Poly(o-anisidine)–tin oxide (POA–SnO2) nanocomposites have been synthesized for the first time through an in situ chemical polymerization of o-anisidine in the presence of SnO2 nanoparticles of 25–40 nm in diameters. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM) were used to characterize the POA–SnO2 nanocomposites. The characterization results confirmed the polymerization of o-anisidine and the strong interaction between POA and SnO2 nanoparticles. Humidity sensing characteristics such as relative humidity (RH)-impedance property, humidity hysteresis, response and recovery times and reproducibility of POA–SnO2 have been investigated. The nanocomposite with 50 wt% SnO2 exhibited better humidity sensing properties than pure POA, such as good sensitivity, fast response (∼87 s), rapid recovery (∼13 s), hysteresis within 4% and excellent repeatability.

Using a single, improved synthetic process, three different compounds comprising two known phases such as [Cu 3 (BTC) 2 (H 2 O) 3 ] ( 1 ), [Cu 2 (OH)(BTC)(H 2 O)] · 2 n H 2 O ( 2 ) and a new phase [Cu(BTC–H 2 ) 2 -(H 2 O) 2 ] · 3H 2 O ( 3 ) have been prepared by microwave-irradiation (MW) of identical reaction mixture of Cu(II) salt and trimesic acid, benzene-1,3,5-tricarboxylic acid (BTC–H 3 ) at different temperatures. The microwave synthesis of ( 1 ) has been compared to its conventional hydrothermal synthesis. It has been found that by using MW synthesis ( 1 ) can be obtained in a much shorter synthesis time with improved yield and physical properties. The effect of other synthetic parameters such as solvent, concentration of reactant mixtures and reaction time on the product ( 1 ) has been also studied. At high temperature, the compound ( 2 ) was obtained in the same solution. The new phase ( 3 ) has been characterized by elemental analysis, thermogravimetric analysis, IR spectroscopy, scanning electron microscopy and powder XRD analysis.

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.

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.

Humidity sensitive poly(2,5-dimethoxyaniline)/WO 3 (PDMA/WO 3 ) composites with different weight percents of WO 3 have been prepared by a simple mechanical mixing method. These composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Humidity sensing characteristics, including the resistance versus relative humidity (RH), humidity hysteresis, response time, repeatability and long-term stability of these composites have been investigated. The PDMA/WO 3 composites show better sensing properties than pure PDMA, such as higher sensitivity, quicker response and small hysteresis. The resistance of the composite with 30 wt% of WO 3 changes linearly over the humidity range (23–84% RH). Furthermore, it exhibits a maximum percentage response factor (∼651 at 87% RH), quick response (humidification, 27 s and desiccation, 136 s), narrow hysteresis (∼5%) and an excellent repeatability of the response.

The present investigation reports the humidity sensing properties of poly(o-anisidine)/WO3 (POA/WO3) composites. The POA/WO3 composites with different WO3 weight percents were prepared by a simple mechanical mixing method. These composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Humidity sensing properties of the composites were investigated, including the resistance versus relative humidity, humidity hysteresis, response time, repeatability and long-term stability. The results indicate that the humidity sensing properties of the POA/WO3 composites are better than those of pure POA. The composites respond more rapidly to humidification and desiccation steps than POA. The composite with 30 wt% of WO3 shows the maximum percentage response factor (Sf) ∼353 at 85% RH, narrow hysteresis (∼6%) and an excellent repeatability of the response. Furthermore, it was found to be stable for more than 30 days.

Mesoporous hybrid material containing urethane moieties in functionalized long chain organic group have been synthesized by using bis[3-(triethoxysilyl) propyl urethane]ethane (BTESPUE) and tetraethoxysilane as structural ingredients. The incorporation of BTESPUE within the framework of mesoporous material was confirmed by Fourier transform-infrared, X-ray photoelectron spectroscopy, solid-state NMR spectroscopy and thermogravimetric analysis. This material had a thick wall and uniform pore, which may be attributed to the hydrogen bonding inside framework due to urethane moieties.

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).

International audience; The adsorption of the xylene mixture onto MIL-101(Cr) has been studied experimentally and theoretically. The adsorption isotherms of the xylene isomers show a high affinity for each isomer with MIL- 101(Cr). This is in good agreement with the enthalpies of adsorption extrapolated at zero coverage, 75 kJ mol 1, 68 kJ mol 1 and 64 kJ mol 1 for o-, m- and p-xylene respectively. The order of these values is consistent with that obtained by the computer simulations. The saturation plateau obtained with p-xylene is higher than that obtained with the adsorption of o- or m-xylene onto MIL-101(Cr). This was discussed in terms of stacking in the cavities of MIL-101(Cr). The filling of the small cavities of MIL-101(Cr) was found more difficult in the case of m-xylene which was interpreted by a weaker interaction with the cavities walls. The chromatographic separation of the xylene mixture was consistent with these results. Different retention times could be found, agreeing the different enthalpies of adsorption for the different isomers. o-Xylene was successfully separated from the xylene mixture.

The recovery of propylene and nitrogen from the stream formed during the resin degassing (70% N 2 /30% C 3 H 6 ) within the polypropylene production process is important from the economic and environmental points of view. This work proposes the use of a pressure swing adsorption process with MIL-100(Fe) as an adsorbent to carry out this separation, either for recovering only nitrogen, or recovering both nitrogen and propylene. Single and binary breakthrough curves were experimentally determined on a lab-scale set-up and simulated to validate the mathematical model. PSA simulation results showed that for the nitrogen recovery process, a product purity of 99.9% and a recovery of 81.5% could be achieved with a power consumption of only 115 Wh/kg N2 . For the nitrogen and propylene recovery process, the products purities obtained were respectively 99.9% for nitrogen and 97.9% for propylene with recoveries of 97.4% and 87.6%. The adsorbent productivity was 0.20 kg N2 /kg ads /h and 0.07 kg C3H6 /kg ads /h. The total power consumption increased to 179 W h/kg N2 or 309 W h/kg C3H6 a value that is still below the ones reported previously in the literature for other technologies.

Water sorption technologies are widely used commercially in many contexts, including industrial or indoor desiccant applications such as desiccant dehumidifiers, gas dryers, adsorptive air conditioning systems, fresh water production, adsorption heat transformation, etc.[1] In recent years, the potential for energy savings through improved efficiency has received increased attention, particularly as low-grade thermal energy or solar energy could be utilized. Currently, silica gel and zeolites are widely utilized commercially, often formed into corrugated honeycomb rotors.[1] As these sorbents typically must be heated above 150 °C during the desorption step, these sorbents are far from ideal in terms of energy consumption. There are additional issues with the level of dehumidification that these materials are able to achieve.[1] Improved energy efficiency requires advanced water adsorbents that can be regenerated together with the removal of a large amount of water vapor from humid conditions.[1] If such materials could operate at or below 80 °C, they could utilize readily available waste heat, leading to further energy savings. Among the existing classes of porous solids, crystalline metal–organic frameworks (MOFs)[2] are currently of great

International audience

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.

[EN] 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. © 2011 The Royal Society of Chemistry., Financial support by the Spanish DGI (CTQ2009-11587 and CTQ2010-18671 and Consolider MULTICAT) is gratefully acknowledged. Prof. Jong-San Chang and his group are thanked for providing us with sufficient quantities of the three MIL-100 (Fe) samples. Korean researchers acknowledge the financial support of KICOS and KRICT for the international collaboration program.