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We report an in situ polymerization strategy to incorporate a thermo-responsive polymer, poly(N-isopropylacrylamide) (PNIPAM), with controlled loadings into the cavity of a mesoporous metal-organic framework (MOF), MIL-101(Cr). The resulting MOF/polymer composites exhibit an unprecedented temperature-triggered water capture and release behavior originating from the thermo-responsive phase transition of the PNIPAM component. This result sheds light on the development of stimuli-responsive porous adsorbent materials for water capture and heat transfer applications under relatively mild operating conditions.

Storing methane in clathrates is one of the most promising alternatives for transporting natural gas (NG) as it offers similar gas densities to liquefied and compressed NG while offering lower safety risks. However, the practical use of clathrates is limited given the extremely low temperatures and high pressures necessary to form these structures. Therefore, it has been suggested to confine clathrates in nanoporous materials, as this can facilitate clathrate's formation conditions while preserving its CH4 volumetric storage. Yet, the choice of nanoporous materials to be employed as the clathrate growing platform is still rather arbitrary. Herein, we tackle this challenge in a systematic way by computationally exploring the stability of clathrates confined in alkyl-grafted silica materials with different pore sizes, ligand densities and ligand types. Based on our findings, we are able to propose key design criteria for nanoporous materials favoring the stability of a neighbouring clathrate phase, namely large pore sizes, high ligand densities, and smooth pore walls. We hope that the atomistic insight provided in this work will guide and facilitate the development of new nanomaterials designed to promote the formation of clathrates., Unravelling structure–property relationships allowing clathrate stability on hydrophobized silica pores. Cyclic and medium-sized chain alkane ligands form suitable ligands for clathrate stabilization.

The molecular connectivity of polymer-metal-organic framework (polyMOF) hybrid materials was investigated using density functional theory calculations and solid-state NMR spectroscopy. The architectural constraints that dictate the formation of polyMOFs were assessed by examining poly(1,4-benzenedicarboxylic acid) (pbdc) polymers in two archetypical MOF lattices (UiO-66 and IRMOF-1). Modeling of the polyMOFs showed that in the IRMOF-1-type lattice, six, seven, and eight methylene (-CH2-) groups between 1,4-benzenedicarboxylate (terephthalate, bdc2-) units can be accommodated without significant distortions, while in the UiO-66-type lattice, an optimal spacing of seven methylene groups between bdc2- units is needed to minimize strain. Solid-state NMR supports these predictions and reveals pronounced spectral differences for the same polymer in the two polyMOF lattices. With seven methylene groups, polyUiO-66-7a shows 7 ± 3% of uncoordinated terephthalate linkers, while these are undetectable (

Proton conducting materials are key components in proton exchange membrane fuel cells for clean energy research. Most such conducting crystalline materials (MOFs/CPs/COFs/HOFs) show limited practical application due to the multistep synthesis of organic ligands and usage of hazardous solvents. To look for simple and highly efficient crystalline proton conducting materials, we present herein a coordination polymer, PCM-1, based on a positively charged [Co(bpy)4(H2O)2]2+ (bpy = 4,4′-bipyridine) backbone. The presence of a cationic unit, anionic nitrates, as well as coordinated and adsorbed water molecules is demonstrated to play a significant role in the water-assisted ultrahigh superprotonic conduction properties. PCM-1 displays a conductivity value of over 10−2 S cm−1 at 98% relative humidity (RH) and 80 °C without any loss of performance over multiple cycles, ranking among the most promising proton conducting materials in the domain of MOFs/CPs/COFs/HOFs. Quasi-elastic neutron scattering (QENS) and molecular simulations were further combined to gain a better understanding of these properties at the molecular level. This joint experimental/modeling study revealed water-assisted proton dynamics through the formation of a long-range H-bonded network mediated by a Teixeira jump diffusion model. Furthermore, this material was shown to be highly stable and easily scalable using a green and simple synthesis process.

A Fe-MOF was obtained from aqueous solution in high yield under reflux. The water sorption properties were studied by powder X-ray diffraction, volumetric and gravimetric sorption experiments and molecular simulations. The subsequent filling of hydrophobic and hydrophilic pores as well as the stability of the material are demonstrated.

The CO2 capture performance of InOF-1 was optimised by confining small amounts of MeOH within its micropores (MeOH@InOF-1). In comparison with fully activated InOF-1, MeOH@InOF-1 shows a 1.30 and 4.88-fold increase in CO2 capture capacity for kinetic and static isothermal CO2 adsorption experiments respectively. Density functional theory calculations coupled with forcefield based-Monte Carlo simulations revealed that such an enhancement is assigned to an increase of the degree of confinement felt by the CO2 molecules resulting from the formation of a lump at the vicinity of the μ2-OH groups since MeOH strongly interacts with these adsorption sites and is thus highly localized in this region.

International audience; A hydrolytically stable metal–organic framework (MOF) material, named KAUST-7′, was derived from a structural phase change of KAUST-7 upon exposure to conditions akin to protonic conduction (363 K/95% relative humidity). KAUST 7′ exhibited a superprotonic conductivity as evidenced by the impedance spectroscopic measurement revealing an exceptional conductivity up to 2.0 × 10–2 S cm–1 at 363 K and under 95% RH, a performance maintained over 7 days. Ab initio molecular dynamics simulations suggested that the water-mediated proton transport mechanism is governed by water assisted reorganization of the H-bond network involving the fluorine moieties in KAUST-7′ and the guest water molecules. The notable level of performances combined with a very good hydrolytic stability positions KAUST-7′ as a prospective proton-exchange membrane alternative to the commercial benchmark Nafion. Furthermore, the remarkable RH sensitivity of KAUST-7′ conductivity, substantially higher than previously reported MOFs, offers great opportunities for deployment as a humidity sensor.

Force field-based and ab initio molecular dynamics simulations are combined with impedance spectroscopy experiments to reveal the high proton conduction performance of a three-dimensional titanium phosphate TiIVTiIV(HPO4)4 under humidity and further elucidate the microscopic mechanism at the origin of the proton transport throughout the porosity of this solid. The molecular simulations revealed that the POH groups in the structure act as a proton source, and the proton is transported from one pore to another through the hydrogen bond network formed by water molecules and the bridging O of the solid. Propitiously, besides its superprotonic behavior with a conductivity of 1.2 × 10–3 S cm–1 at room temperature and 95% relative humidity, this material is one of the best porous solids reported to date in terms of efficiency for proton transfer with a resulting activation energy (0.13 eV) as low as that reported for Nafion commercially used as electrolyte membrane in fuel cells. Furthermore, this solid shows a ...

The proton-conduction performances of the chemically stable porous zirconium phenolate MIL-163 MOF were characterized for the first time by complex impedance spectroscopy. Whereas this large square-shaped channel-like MOF exhibits very poor conductivity under anhydrous conditions, measurements performed at 90 °C and 95% relative humidity evidenced a superprotonic behavior with a conductivity of 2.1 × 10–3 S·cm–1, among the highest values reported so far for water-stable MOFs. This experimental investigation was further supported by Monte Carlo simulations to shed light on the effects of both the guest molecules (i.e., dimethylamine and water) and the acidic protons from the constitutive inorganic chains on the conduction properties of this porous hybrid solid. It was found that the water molecules form a three-dimensional hydrogen-bond network leading to the formation of multiple pathways that bridge the acidic Zr-bonded phenol groups of the organic linker, which act as a proton source. The dimethylamine ...

Two new polymethoxylated flavonoids, 2′,5′,6′-trimethoxy-[2″,3″ : 3′,4′]furano dihydrochalcone and 2,4′,4,5-tetramethoxy-[2″,3″ : 6,7]-furanodihydroaurone, were isolated from the root barks of Lonchocarpus araripensis, along with the known compounds 3,4,5,6-tetramethoxy-[2″,3″ : 7,8]-furanoflavan, 3,6-dimethoxy-1″,1″-dimethylcromene-[2″,3″ : 7,8]-flavone, 3′,4′-methylenodioxy-5,6-dimethoxy-[2″,3″ : 7,8]-furanoflavone, 3,5,6-trimethoxy-[2″,3″ : 7,8]-furanoflavanone, 3,5,6-trimethoxy-[2″,3″ : 7,8]-furanoflavone, and 6α-hydroxy-medicarpin. The complete 1H and 13C NMR assignments of the new furan flavonoids were performed using 1D and 2D pulse sequences, including COSY, HSQC, and HMBC experiments, and comparison with spectral data for analog compounds from the literature, particularly for the new furanodihydroaurone because of several inconsistencies on the carbonyl chemical shifts from the literature. Copyright © 2008 John Wiley & Sons, Ltd.

The adsorption equilibrium of methane in PCN-14 was simulated by the Monte Carlo technique in the grand canonical ensemble. A new force field was proposed for the methane/PCN-14 system, and the temperature dependence of the molecular siting was investigated. A detailed study of the statistics of the center of mass and potential energy showed a surprising site behavior with no energy barriers between weak and strong sites, allowing open metal sites to guide methane molecules to other neighboring sites. Moreover, this study showed that a model assuming weakly adsorbing open metal clusters in PCN-14, densely populated only at low temperatures (below 150 K), can explain published experimental data. These results also explain previously observed discrepancies between neutron diffraction experiments and Monte Carlo simulations.