Water–mineral interfaces are important for several environmental, industrial, biological, and geological processes. Gypsum, CaSO4·2H2O, is a widespread mineral of high technological, medical, and environmental relevance, but little is known about its surface structure and its interaction with water. A molecular-level understanding of gypsum/water interface is given here by a combined experimental/theoretical study. We investigate the structure and dynamics of water adsorbed from vapor on the gypsum (010) single-crystal surface at room temperature, combining sum-frequency generation (SFG) vibrational spectroscopy experiments and ab initio molecular dynamics (AIMD) simulations. The SFG spectra of gypsum at low relative humidity (RH) show an anisotropic arrangement of structural water molecules and the presence of dangling OH groups. The AIMD simulations allow a detailed assignment of the SFG spectra and show that the cleaved (010) surface rearranges to have only 25% of the OH groups pointing away from the surface. At higher RHs, the first adsorbed water layer binds to these OH groups and forms an anisotropic arrangement, but with the amount of free OH groups significantly suppressed and without any significant diffusion. Upon adsorption of a second water layer, although the topmost layer of molecules is more disordered and dynamic than the previous one, its structure is still influenced by the gypsum surface underneath because it has a much reduced amount of free OH groups with respect to the free surface of water, and a slower surface diffusion with respect to bulk water. The theoretical results corroborate the experimental ones and provide an accurate atomic characterization of the surface structure.

The prolific topic of development of solidstate lighting devices has focused over the last years on solid-state white light (SSWL) emitting materials, mainly due the long operation lifetime and excellent harvesting and saving energy. [1] Even today, incandescent and mercury-based fluorescent materials are employed as white-light sources due to their superior warm-white light impression. Moreover, the fabrication of environmentally safe white light-emitting diode (LEDs) with a "warm-white" impression remains still a challenge. Many of the "white" organic light-emitting diode/ LED materials cover only part of the visible spectrum and lack the required efficacy of 150-200 lm W −1 for white-light performance. [2] For this reason, the design of a new generation of SSWL materials is of continuous interest in materials science, especially in areas such as full-color flat-panel electroluminescent displays for mobile devices, optical telecommunications, lighting, and backlighting for liquid-crystals displays. [3] Besides, high-quality white-light performance requires the Commission International de l'Eclairage (CIE) x,y coordinates 0.333, 0.333, with a correlated color temperature (CCT) into the 2500-6500 K, and color rendering index above 80 which are standard requirements for lighting applications. [4] One of the explored strategies to obtain white light is by combining red, green, and blue (RGB) sources to cover the visible region (400-700 nm) in the electromagnetic spectrum. [5] Also, metal-organic frameworks (MOFs) have been the focus of interest due to their potential applications in gas storage/ separation , [6] catalysis, [7] optics, [8] magnetism, [9] sensing, [10] and biomedicine. [4,11,12] Due to a permanent porosity, structural diversity, functionalization capabilities and then, tunable luminescence, MOF possess interesting properties for the development of SSWL composites. In recent years, a large number of luminescent MOFs have been reported for this purpose. [5,13-24] Moreover, for uses in nanotechnology, it is mandatory that MOFs are anchored on solid substrates, being particularly evident in the case of optoelectronic applications. [25,26] According to specialized reviews such as those from Wöll group, [27] it is distinguishable the surface-supported metal-organic frameworks (SURMOFs) devices, fabricated using layer-by-layer (LbL) A new set of Ln-MOF (lanthanide-metal-organic framework) thin films, known as Ln-SURMOFs (surface-supported MOFs), is fabricated with a layer-by-layer, in order to generate solid-state white-lighting devices. A three-component approach is carried out for a rational combination of red, green, and blue (RGB) emitting Eu 3+ , Tb 3+ , and Gd 3+ containing layers in order to achieve white-light emission. The Ln-SURMOFs are fully characterized by powder X-ray diffraction, infrared reflection-absorption spectroscopy, scanning electron microscopy, and photoluminescence spectroscopy (excitationemission and chromaticity determination according to Commission International de l'Eclairage, C...

Lanthanide-based crystalline coatings have a great potential for energy-conversion devices, but until now luminescent surface-anchored materials were difficult to fabricate. Thin films, called lanthanides surface-mounted metal–organic frameworks (SURMOFs) with tetrasubstituted halide (fluorine, chlorine, and bromine) terephthalic acid derivative linkers as a basic platform for optical devices, exhibit a high quantum yield of fluorescence visible to the naked eyes under ambient light. We show that we can tune the luminescent properties in thin films by halide substitution, which affords control over the molecular structure of the material. We rationalize the mechanism for the modulation of the photophysical properties by “antenna effect”, which controls the energy transfer and quantum yields using experimental and theoretical techniques for chelated lanthanides as a function of the type of atom substitutions at the phenyl rings and the resulting dihedral angle between phenyl rings in the linkers and carboxylate groups.

We herein present a case study on the templated, Pd-catalyzed polymerization reaction of methyl propiolate in the confined pore space of three different surface anchored metal-organic framework (SURMOFs) systems in...

Electromagnetic, external stimuli can be used to switch Metal-Organic Framework (MOF) materials and to achieve control over the pores of these materials on different ways. We designed MOFs with switchable moieties in their side-chains, such as azobenzene, to be switchable under irradiation of UV/Vis light. Additionally, we developed devices to be able to measure the impact of electromagnetic fields in-situ. We focused on surface anchored MOF (SURMOF) thin films, deposited on asymmetric, porous α-Al2O3 supports as gas separation membrane layers. It is possible to control the gas transport properties of the materials using, but also using electric fields, and measure changes gas separation (permeability and selectivity) of binary mixtures in-situ, using the Wicke-Kallenbach technique. The light switchable systems were investigated on their CO2 separation performance: By switching the azobenzene between cis and trans isomers inside the pore windows, it was possible to switch dipolar moments, thus changing the adsorption properties towards the quadrupolar moment of CO2. Using electric fields of 500 V/mm we could show on the prominent example of ZIF-8, a zeolitic imidazolate framework, that it has a strong impact on the gas transport properties, especially looking at the molecular sieving. The mechanistic of the electric field influence on the ZIF is as follows: The electric field distorts the lattice of the MOF, shifting the Zn2+ ions, lowering the symmetry of the unit cell. This effect leads to polarized polymophs of the structure, sharpening the molecular sieving through a stiffening effect. The purification of Propylene/Propane, a highly desired separation for the plastics industry, could be increased through the electric field stimuli by 33%. References Knebel, A. et al. Defibrillation of soft porous metal-organic frameworks with electric fields. Science 358, 347–351; 10.1126/science.aal2456 (2017). Wang, Z. et al. Tunable molecular separation by nanoporous membranes. Nat. Commun. 7, 13872; 10.1038/ncomms13872 (2016). Müller, K. et al. Switching Thin Films of Azobenzene-Containing Metal-Organic Frameworks with Visible Light. Chem. Eur. J. 23, 5434–5438; 10.1002/chem.201700989 (2017). Knebel, A. et al. Azobenzene Guest Molecules as Light-Switchable CO 2 Valves in an Ultrathin UiO-67 Membrane. Chem. Mater. 29, 3111–3117; 10.1021/acs.chemmater.7b00147 (2017). Tan, N. Y. et al. Investigation of the terahertz vibrational modes of ZIF-8 and ZIF-90 with terahertz time-domain spectroscopy. Chem Commun 51, 16037–16040; 10.1039/c5cc06455d (2015). Figure 1

Metal-Organic Frameworks, consisting of inorganic nodes and organic linker molecules, are (mainly) porous materials with record holding inner surface areas, tailor-made properties, and adjustable pore windows. External stimuli on MOFs can be applied and achieve control over crystallization, gas transport properties, pore windows, and many other effects: breathing, dipolar moment, etc., which is extremely interesting for membrane science.The keynote will present an overview on novel types of applied physics to membrane separations to enhance green production and carbon capture: we can use novel MOF materials as porous liquids or MOF thin films and influence their properties with external stimuli, such as electromagnetic fields. This leads to interesting interactions: adsorption and desorption can be changed, as well as an in-situ control over the continuous gas separation on the nanometer scale can be done through membrane layers.