Flexible nanoporous chromium or iron terephtalates (BDC) MIL-53(Cr, Fe) or M(OH)[BDC] have been used as matrices for the adsorption and in vitro drug delivery of Ibuprofen (or alpha- p-isobutylphenylpropionic acid). Both MIL-53(Cr) and MIL-53(Fe) solids adsorb around 20 wt % of Ibuprofen (Ibuprofen/dehydrated MIL-53 molar ratio = 0.22(1)), indicating that the amount of inserted drug does not depend on the metal (Cr, Fe) constitutive of the hybrid framework. Structural and spectroscopic characterizations are provided for the solid filled with Ibuprofen. In each case, the very slow and complete delivery of Ibuprofen was achieved under physiological conditions after 3 weeks with a predictable zero-order kinetics, which highlights the unique properties of flexible hybrid solids for adapting their pore opening to optimize the drug-matrix interactions.

The unusual adsorption behavior of CO2 in a nanoporous hybrid metal– organic solid is discussed (see figure). The results indicate that the gas adsorption–desorption step is related to a breathing phenomenon. This study also suggests that the main interactions responsible for the breathing phenomenon are strong guest–framework CO2–OH interactions as well as CO2–CO2 interactions along the tunnels present in the structure.

The synthesis of the commercially available aluminum fumarate sample A520 has been optimized and its structure analyzed through a combination of powder diffraction, solid-state NMR spectroscopy, molecular simulation, IR spectroscopy, and thermal analysis. A520 is an analogue of the MIL-53(Al)-BDC solid, but with a more rigid behavior. The differences between the commercial and the optimized samples in terms of defects have been investigated by in situ IR spectroscopy and correlated to their catalytic activity for ethanol dehydration.

The microscopic interfacial structures for a series of metal–organic frameworks (MOFs)/polymer composites consisting of the Zr-based UiO-66 coupled with different polymers are systematically explored by applying a computational methodology that integrates density functional theory calculations and force field-based molecular dynamics simulations.

An innovative computational methodology integrating density functional theory calculations and force field-based molecular dynamics simulations was developed to provide a first microscopic model of the interactions at the metal-organic framework (MOF) surface/polymer interface. This was applied to the case of the composite formed by the polymer of intrinsic microporosity, PIM-1, and the zeolitic imidazolate framework, ZIF-8, as a model system. We found that the structure of the composite at the interface is the result of both the chemical affinity between PIM-1 and ZIF-8 and the rigidity of the polymer. Specifically, there is a preferential interaction between the -CN groups of PIM-1 and the NH terminal functions of the organic linker at the ZIF-8 surface. Additionally, the resulting conformation of the polymer gives rise to interfacial microvoids at the vicinity of the MOF surface. The porosity, rigidity, and density of the interfacial polymer were analyzed and compared to those for the bulk polymer. It was shown that the polymer still feels the impact of the MOF surface even at long distances above 15-20 Å. Further, both the polydispersity of the polymer and the flexibility of the MOF surface were revealed to only slightly affect the properties of the MOF/interface. This work, which delivers a microscopic picture of the MOF surface/polymer interactions at the interface, would lead, in turn, to the understanding of the compatibility in MOF-based mixed-matrix membranes.

Grand Canonical Monte Carlo simulations have explained the breathing of a metal-organic framework upon CO(2) adsorption, first suggested by microcalorimetry.

A comprehensive DFT study of the possible CO2 adsorption geometries in the MIL-53 (Al, Cr) and MIL-47 hybrid organic−inorganic materials has been performed, as a preliminary step to gain a deeper understanding of the CO2 adsorption mechanism in these systems and to help explain the “breathing” effect displayed by the MIL-53 materials. This technique allows us to explore the possible spatial configurations of the CO2 molecules in the MIL-53 systems depending on the size of the pore opening at different loadings. Our results show that the replacement of the μ2-OH groups by oxo moieties in the MIL-47 material leads to fewer, weaker adsorption sites for CO2 onto the framework itself, whereas a larger number of CO2 geometries are possible in both the large and narrow versions of MIL-53. In the narrow pore form, the double interaction, where a CO2 molecule bridges the pore to simultaneously coordinate with 2 μ2-OH groups on opposite sides of a pore wall, was predicted to be the most energetic arrangement at the initial stage of adsorption. Additional configurations include coordination with both inorganic and organic parts of the framework. When the number of CO2 molecule increases, our calculations indicate that the resulting increase in the intermolecular interactions between the adsorbate molecules lead to a significant modification of the CO2 arrangement within the pore and should be an important feature in the explanation of the “breathing” of this material. In the large pore form, an interaction reflecting the opening of the pore is not possible, and so the most likely interaction is one where a CO2 interacts with a single μ2-OH group, in a number of different orientations.

Porous titanium oxide materials are attractive for energy-related applications. However, many suffer from poor stability and crystallinity. Here we present a robust nanoporous metal–organic framework (MOF), comprising a Ti12O15 oxocluster and a tetracarboxylate ligand, achieved through a scalable synthesis. This material undergoes an unusual irreversible thermally induced phase transformation that generates a highly crystalline porous product with an infinite inorganic moiety of a very high condensation degree. Preliminary photophysical experiments indicate that the product after phase transformation exhibits photoconductive behavior, highlighting the impact of inorganic unit dimensionality on the alteration of physical properties. Introduction of a conductive polymer into its pores leads to a significant increase of the charge separation lifetime under irradiation. Additionally, the inorganic unit of this Ti-MOF can be easily modified via doping with other metal elements. The combined advantages of this compound make it a promising functional scaffold for practical applications.