A new MIL-101 material based on aluminum and containing amine functional groups has been synthesized. The pure phase NH2-MIL-101(Al) can only be formed in very specific synthesis conditions, where both the metal source and the solvent used play a key role. The resulting porous solid shows a high thermal and chemical stability, decomposing at temperatures above 650 K in air. The NH2-MIL-101(Al) framework offers an excellent trade off for separation of CO2: the combination of high stability, acceptable capacity at low adsorbate partial pressures, high selectivity, and fast regenerability makes this new material a very attractive candidate for applications like natural gas or biogas upgrading. CO2 capacities up to 62 wt % are obtained at room temperature and 3 MPa. In addition to an excellent separation performance, the NH2-MIL-101(Al) shows a high activity in the basic catalyzed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate at 313 K even in an as apolar a solvent as toluene (turn over frequency, TOF = 1.8 h–1).

Mixed matrix membranes (MMMs) composed of a glassy polymer (polysulfone) and the flexible metal organic framework NH(2)-MIL-53(Al) exhibit excellent separation properties. In contrast to most reported membranes, CO(2)/CH(4) separation selectivity increases with pressure, related to the flexibility of the filler.

Several archetypical metal organic frameworks (MOFs), namely, HKUST-1, ZIF-8, MIL-100(Al), MIL-53(Al), and NH2-MIL-53(Al), were synthesized via anodic dissolution in an electrochemical cell. The influence of different reaction parameters such as solvent, electrolyte, voltage–current density, and temperature on the synthesis yield and textural properties of the MOFs obtained was investigated. The characterization of the samples involved X-ray diffraction, gas adsorption, atomic force microscopy, diffuse reflectance infrared Fourier transform spectroscopy, and scanning electron microscopy. In the present article, we demonstrate that electrochemical synthesis is a robust method offering additional degrees of freedom in the synthesis of these porous materials. The main advantages are the shorter synthesis time, the milder conditions, the facile synthesis of MOF nanoparticles, the morphology tuning and the high Faraday efficiencies. The synthesized MIL-53 and NH2-MIL-53 samples exhibit suppressed framework flexibility compared to samples synthesized solvothermally.

Hybrid materials bearing organic and inorganic motives have been extensively discussed as playgrounds for the implementation of atomically resolved inorganic sites within a confined environment, with an exciting similarity to enzymes. Here, we present the successful design of a site-isolated mixed-metal Metal Organic Framework that mimics the reactivity of soluble methane monooxygenase enzyme and demonstrates the potential of this strategy to overcome current challenges in selective methane oxidation. We describe the synthesis and characterisation of an Fe-containing MOF that comprises the desired antiferromagnetically coupled high spin species in a coordination environment closely resembling that of the enzyme. An electrochemical synthesis method is used to build the microporous MOF matrix while integrating the atomically dispersed Fe active sites in the crystalline scaffold. The model mimics the catalytic C-H activation behaviour of the enzyme to produce methanol, and shows that the key to this reactivity is the formation of isolated oxobridged Fe units.

Mixed matrix membranes (MMMs) composed of metal organic framework (MOF) fillers embedded in a polymeric matrix represent a promising alternative for CO2 removal from natural gas and biogas. Here, MMMs based on NH2‐MIL‐53(Al) MOF and polyimide are successfully synthesized with MOF loadings up to 25 wt% and different thicknesses. At 308 K and ΔP = 3 bar, the incorporation of the MOF filler enhances CO2 permeability with respect to membranes based on the neat polymer, while preserving the relatively high separation factor. The rate of solvent evaporation after membrane casting proves key for the final configuration and dispersion of the MOF in the membrane. Fast solvent removal favours the contraction of the MOF structure to its narrow pore framework configuration, resulting in enhanced separation factor and, particularly, CO2 permeability. The study reveals an excellent filler‐polymer contact, with ca. 0.11% void volume fraction, for membranes based on the amino‐functionalized MOF, even at high filler loadings (25 wt%). By providing precise and quantitative insight into key structural features at the nanoscale range, the approach provides feedback to the membrane casting process and therefore it represents an important advancement towards the rational design of mixed matrix membranes with enhanced structural features and separation performance.

MOFs scattering away: The mechanism behind the multistep synthesis of two metal–organic frameworks sharing the same metal and organic precursors was revealed by in situ time‐resolved small‐ and wide‐angle X‐ray scattering. Key factors governing the crystal assembly could be established (see picture: C gray, H white, N blue, O red, Al yellow, Cl green), including solvent, temperature, and precursor concentration.

We report a series of powder X-ray diffraction experiments performed on the soft porous crystals MIL-53(Al) and NH-MIL-53(Al) in a diamond anvil cell under different pressurization media. Systematic refinements of the obtained powder patterns demonstrate that these materials expand along a specific direction while undergoing total volume reduction under an increase in hydrostatic pressure. The results confirm for the first time the Negative Linear Compressibility behaviour of this family of materials recently predicted from quantum chemical calculations.

ABSTRACT:The metal−organic framework NH 2 -MIL-53(Al) is the first solid-state material displaying nonlinear optical switching due to a conformational change upon breathing. A switching contrast of at least 38 was observed. This transition originates in the restrained linker mobility in the very narrow pore configuration.T he field of nonlinear optics has experienced an everincreasing interest due to multiple applications in information processing, electro-optical switching, and telecommunications.1,2 While commercial nonlinear optical (NLO) materials are still largely inorganic, organic compounds and metal−organic complexes have attracted much attention.3 As a result, during the past decade, the possibility of changing the quadratic or second-order NLO response by an external stimulus has been increasingly addressed. A molecule or solid able to change its NLO response reversibly is called an "NLO switch". Several families of molecules and metal−organic complexes display this property in the liquid phase.4−9 NLO switches in the solid state, however, are much more scarce. A necessary requirement for a quadratic NLO material is that it be noncentrosymmetric. While it is easy to synthesize individual noncentrosymmetric molecules and metal−organic complexes, these typically dipolar entities often organize in an antiparallel fashion into centrosymmetric crystals. A common strategy to obtain polar order on the macroscopic level is via electric field poling of polymers containing dipolar chromophores. The change of centrosymmetric to noncentrosymmetric order is associated with a large change in quadratic NLO response, but the change is not readily reversible.10 As a consequence, hardly any reversible solid-state second-order NLO switches have been reported to date: only anil crystals (Schiff bases, based on photoswitching)11−14 and thin films of ruthenium complexes (based on redox switching) 15 have been shown to display a certain degree of reversible switching. For these materials, the NLO contrast, defined as the ratio of the second harmonic generation (SHG) intensities (see below) before and after the external stimulus, varies by a factor between 1.3 and 10. This limited contrast is due to the fact that all reported NLO switches essentially retain their noncentrosymmetric order upon switching. Herein we report that the metal−organic framework (MOF) NH 2 -MIL-53(Al), which contains Al 3+ and 2-aminoterephthalate, is a novel solid reversible NLO switch. The switching capacity is due to a reversible conformational change that greatly diminishes the polar ordering of the material.MOFs have also attracted a lot of scientific attention in the field of nonlinear optics, where the design of several noncentrosymmetric frameworks has been reported. 16−19 In a single case, the SHG intensity of a MOF could be modulated by cation exchange, with a contrast of 1.75. 20 However, the effects of organic guest molecules on the SHG intensity have not been reported to date.A special class of MOFs are those that can reversibly alter the...