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International audience; The emission of polar volatile organic compounds (VOCs) is a major worldwide concern of air quality and equally impacts the preservation of cultural heritage (CH). The challenge is to design highly efficient adsorbents able to selectively capture traces of VOCs such as acetic acid (AA) in the presence of relative humidity (RH) normally found at storage in museums (40-80%). Although the selective capture of VOCs over water is still challenging, Metal-Organic Frameworks (MOFs) possess highly tunable features (Lewis, Bronsted or redox metal sites, functional groups, hydrophobicity…) suitable to selectively capture a large variety of VOCs. In this context, we have explored the adsorption efficiency of a series of MOFs thin films (ZIF-8(Zn), MIL-101(Cr) and UiO-66(Zr)-2CF3) for the selective capture of AA based on a UV/Vis and FT-IR spectroscopic ellip-sometry in operando study (2-6% of relative pressure of AA under 40% of RH), namely conditions close to the realistic envi-ronmental storage conditions of cultural artefacts. For that purpose, optical quality thin films of MOFs were prepared by dip-coating and their AA adsorption capacity and selectivity were evaluated under humid conditions by measuring the variation of the refractive index as a function of the vapor pressures while the chemical nature of the co-adsorbed analytes (water and AA) was identified by FT-IR ellipsometry. While thin films of ZIF-8(Zn) strongly degraded when exposed to AA/water va-pors, films of MIL-101(Cr) and UiO-66(Zr)-2CF3 present a high chemical stability under those conditions. It was shown that MIL-101(Cr) presents a high AA adsorption capacity due to its high pore volume, but exhibits a poor AA adsorption selectivi-ty under humid conditions. In contrast, UiO-66(Zr)-2CF3 was shown to overpass MIL-101(Cr) in terms of AA/ H2O adsorp-tion selectivity and AA adsorption/desorption cycling stability thanks to its high hydrophobic character, suitable pore size for adequate confinement and specific interactions.

International audience; Owing to their high and tunable porosity as well as great chemical diversity, metal–organic frameworks (MOFs) have shown great promise over the past 20 years for a wide range of applications, including gas storage/separation, catalysis, and biomedicine. To date, MOF nanoparticles (NPs) have mostly been obtained as polycrystalline powders or spherical nanocrystals while anisotropic MOFs nanocrystals have been less explored and are of interest in the fields of catalysis, sensing, and electronics. One of the main challenges for the practical application of MOFs is thus to control the crystal size, morphology, and multiscale porosity of these materials while developing adequate shaping strategies. In this review, we cover recent advances in the different synthetic strategies of one-dimensional (1D) MOF nanocrystals as well as hierarchical porous superstructures based on tubular MOFs. We describe the architectures based on MOFs nanotubes (NTs), nanowires (NWs), and nanorods (NRs). Our discussion is focused on the synthetic approaches that drive the structure, crystallinity, size, and morphology of these hierarchical porous hybrid materials. Finally, their potential for different applications is presented.

Supramolecular Thermo Aero-able Gelators (STAGs): tartaric acid, urea, and guanidine with amide and imine moieties as supramolecular synthons are introduced to cross-link and aerate ('aero-able') polyacrylate networks for synthesis of hydrogels. They are bi-functional hence present a greener alternative to the existing cross-linkers and gelators., 9 pages, 9 figures

The thermal stability of short alkanethiol $CH_3(CH_2)_7SH (C_8)$ and long $C_1_8$ self-assembled monolayers (SAMs) is investigated using grazing angle reflection-absorption infrared spectroscopy, cyclic voltammetry, and molecular dynamics simulation. We track the disordering of SAM by untilting and gauche defect accumulation with increasing temperature in the 300-440 K range, a range of interest to tribology. Molecular dynamics simulation with both fully covered and partially covered $C_6, C_8, and C_1_8$ monolayers brings out the morphological changes in the SAM, which may be associated with the observed thermal stability characteristics. The molecular dynamics simulations reveal that short-chain $C_6$ and $C_8$ alkanethiols are more defective at lower temperature than the long-chain $C_1_8$ alkanethiol. With increasing temperature disorder in the SAM, as reflected in both untilting and gauche defect accumulation, tends to saturate at temperatures below 360 K for short-chain SAMs such that any further increase in temperature, until desorption, does not lead to any significant change in conformational order. In contrast the disorder in the long-chain $C_1_8$ SAM increases monotonically with temperature beyond 360 K. Thus, in a practical range of temperature, the ability of a SAM to retain order with increasing thermal perturbations is governed by the state of disorder prior to heat treatment. This deduction derived from molecular dynamics simulation helps to rationalize the significant difference we have observed experimentally between the thermal response of short- and long-chain thiol molecules.

Thermal stability behavior of 1H, 1H,2H,2H-perfluorooctyl trichlorosilane self-assembled on aluminum substrates is characterized using a grazing-angle Fourier transform infrared spectrometer, Fourier transform-Raman spectroscopy, and contact angle measurements. The self-assembled monolayer (SAM) is heated quasi-statically from room temperature to above 633 K with a heating rate of 1 K/s. Variations in peak frequencies, integrated areas of intensities of symmetric and antisymmetric CF2 stretches, and the relative tilt angle of the SAM are reported. We find that the conformational order in the SAM is not disrupted because of thermal cycling when the peak temperature is below 423 K. When the peak temperature is between 423 and 603 K, the cycling results in only a partial retention of the original order. When the peak temperature is above 603 K, the process is completely irreversible. Surface-enhanced Raman spectroscopy and contact angle measurements support these observations. We confirm these trends for a longer chain (1H,1H,2H,2H-perfluordecyl trichlorosilane) molecule of the same family using the same techniques. We discuss the possible reasons for the changes in light of the tilting-untilting and uncoiling-coiling of the helical silane monolayer.