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The development of convenient, non-complicated, and cost-efficient processing techniques for packing low-density MOF powders for industry implementation is essential nowadays. To increase MOFs’ availability in industrial settings, we propose the synthesis of a novel 3D Tb-MOF (1) and a simple and non-expensive method for its immobilization in the form of pellets and membranes in polymethacrylate (PMMA) and polysulphone (PSF). The photoluminescent properties of the processed materials were investigated. To simulate industrial conditions, stability towards temperature and humidity have been explored in the pelletized material. Water-adsorption studies have been carried out in bulk and processed materials, and because of the considerable capacity to adsorb water, proton-conduction studies have been investigated for 1.

The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H2O)] with Ln = Eu3+, Gd3+, Tb3+, Dy3+, Ho3+ and Yb3+ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO3)3·xH2O with the 1,3-bis(carboxymethyl)imidazolium [HL] ligand and oxalic acid (H2ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostructural networks of formula [Tb1−xEux(L)(ox)(H2O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as luminescent ratiometric thermometers based on the emission intensities of ligand, Tb3+ and Eu3+. The best sensitivities were obtained using the ratio between the emission intensities of Eu3+ (5D0→7F2 transition) and of the ligand as the thermometric parameter. [Tb0.97Eu0.03(L)(ox)(H2O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%·K−1 at 340 K.

In this work, we used the rigid tetrapodal organic linker, [1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonic acid) (H8btp), for the preparation of two lanthanide–organic framework families of compounds: layered [Ln7(H5btp)4(H5.5btp)2(H6btp)2(H2O)12]∙23.5H2O∙MeOH [where Ln3+ = Eu3+ (1Eu) and Gd3+ (1Gd)], prepared using microwave-irradiation followed by slow evaporation; 3D [Ln4(H3btp)(H4btp)(H5btp)(H2O)8]∙3H2O [where Ln3+ = Ce3+ (2Ce), Pr3+ (2Pr), and Nd3+ (2Nd)], obtained from conventional hydro(solvo)thermal synthesis. It is shown that in this system, by carefully selecting the synthetic method and the metal centers, one can increase the dimensionality of the materials, also increasing structural robustness (particularly to the release of the various solvent molecules). Compound 1 is composed of 2D layers stacked on top of each other and maintained by weak π–π interactions, with each layer formed by discrete 1D organic cylinders stacked in a typical brick-wall-like fashion, with water molecules occupying the free space in-between cylinders. Compound 2, on the other hand, is a 3D structure with small channels filled with crystallization water molecules. A full solid-state characterization of 1 and 2 is presented (FT-IR spectroscopy, SEM microscopy, thermogravimetric studies, powder X-ray diffraction and thermodiffractometry). The photoluminescence of 1Eu was investigated.

Hydrothermal reactions between rare-earth (RE) chloride salts and N-(carboxymethyl)iminodi(methylphosphonic acid) (H5cmp) led to the isolation of a series of layered networks formulated as [RE(H2cmp)(H2O)] [RE3+= Y3+, La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+and Er3+]. All compounds were isolated as micro-crystalline powders (many of which were nano-sized in thickness), with the plate-like crystallites found to exhibit preferential growth perpendicular to the [002] vector, a feature which seems to favour catalytic performance. Full structural elucidation was attained by the combination of synchrotron radiation (micro-crystal and powder) diffraction data, solid-state NMR studies (1H, 13C and 31P) and photophysical measurements. Materials consist of ∞2[RE(H2cmp)(H2O)] layers in the abplane of the unit cell, constructed from a single RE3+centre (in a highly distorted dodecahedral coordination environment with one water molecule in the first coordination sphere) and one H2cmp3−ligand present in a zwitterionic form. Connections between layers along the c-axis are assured by strong and highly directional O–HO hydrogen bonds involving the protonated phosphonate group (donor) of one layer and one oxygen atom (acceptor) of the carboxylate group in the adjacent layer. The network is an unprecedented 12-connected uninodal plane net with total Schäfli symbol 330.434.52. The Eu3+material is photoluminescent at room temperature and 12 K with 5D0lifetimes of 0.86 ± 0.01 ms and 0.89 ± 0.01 ms, respectively. Studies of the mixed-lanthanide diluted [(Gd0.95Eu0.05)(H2cmp)(H2O)] material showed that Gd3+-to-Eu3+energy transfer occurs within the layers. The coordinated water molecule plays a decisive role in the non-radiative relaxation process of the Eu3+emission. All synthesised materials were further tested in the cyclodehydration of xylose to furfural, with the observed results comparing quite favourably with those from other solid acid catalysts used in the same reaction under similar conditions. A detailed catalytic study was performed for [Y(H2cmp)(H2O)]: selectivity increased to 84% as the conversion reached 83%; this solid was also re-used successfully in three consecutive 4 h runs after separation from the liquid phase by centrifugation and regeneration using either thermal treatment at 280 °C or repeated washing with solvents. All materials have been routinely characterized using vibrational spectroscopy (ATR-FT-IR and FT-Raman), thermogravimetric analyses, SEM investigations and CHN elemental composition. [ABSTRACT FROM AUTHOR]

A series of zeolite-type silicates containing stoichiometric amounts of Ln3+ ions in the framework (Ln-AV-9 materials), with composition (Na4K2)(Ln2Si16O38)·10H2O (Ln = Nd, Sm, Eu, Tb, Gd, Dy) has recently been synthesized and characterized. They form paramagnetic microparticles, which as aqueous suspensions have negligible water 1H longitudinal relaxivities (r1) for all Ln3+ ions studied and quite large transverse relaxivities (r2). In this work we further analysed the size distribution of the Ln-AV-9 particles and their r2* and r2 relaxivities. The r2* relaxivity effects are explained by the static dephasing regime (SDR) theory. The r2 relaxivities appear to be strongly dependent on the interval between two consecutive refocusing pulses (τCP) in the train of 180° pulses applied. For long τCP values, the r2 of the systems saturates at a value, which is always an order of magnitude smaller than r2*. These features are explained by a crude model, which takes into account the residual diffusion effect in the static dephasing regime. The large microparticles, although not efficient in T1 relaxation, are quite effective in enhancing T2 relaxation, particularly at high magnetic fields. The r2* values and the saturation values for r2 were found to increase linearly with B0 and μ02. The largest transversal relaxation rate enhancements were observed for Dy-AV-9 with a saturation value of r2 of 60 s−1 mM−1 and a r2* value of 566 s−1 mM−1 at 9.4 T and 298 K. [ABSTRACT FROM AUTHOR]

The first examples of nanoparticles of pure layered Ln 2(SiO 4H)(OH) 2(H 2O)Cl (where Ln = Eu, Gd, and Tb) and mixed microcrystalline layered lanthanide silicates containing different Eu/Gd and Tb/Gd ratios have been reported. The crystal structure of these silicates has been solved from synchrotron powder X-ray diffraction data. These materials display interesting and tuneable photoluminescence (PL) properties, such as energy transfer between different Ln 3+centers, illustrated here with the pairs Eu 3+/Gd 3+and Tb 3+/Gd 3+. The PL properties of the mixed Eu 3+/Gd 3+sample change upon F –for Cl −ion exchange, and this raises the possibility that this material may be exploited for sensing these ions. [ABSTRACT FROM AUTHOR]

The dehydratation process of layered lanthanide silicates K3LnSi3O8(OH)2, Ln Y, Eu, Tb, and Er, and the structural characterization of the obtained small-pore framework K3LnSi3O9, Ln Y, Eu, Tb, and Er solids, named AV-23, have been reported. The structure of AV-23 has been solved by single-crystal X-ray diffraction (XRD) methods and further characterized by chemical analysis, thermogravimetry, scanning electron microscopy, and 29Si MAS NMR. The photoluminescence (PL), radiance, and lifetime values of AV-23 have been studied and compared with those of AV-22. Both materials have a similar chemical makeup and structures sharing analogous building blocks, hence providing a unique opportunity for rationalizing the evolution of the PL properties of lanthanide silicates across dimensionality. Although Tb-AV-23 contains a single crystallographic Tb3site, PL spectroscopy indicates the presence of Ln3centers in regular framework positions and in defect regions. PL evidence suggests that Eu-AV-23 contains a third type of Ln3environment, namely, Eu3ions replacing Kions in the micropores. The radiance values of the Tb-AV-22 and Tb-AV-23 samples are of the same order of magnitude as those of standard Tb3green phosphors. For the samples K3(Y1-aEraSi3O9), a0.005−1, efficient emission and larger 4I132lifetimes (ca. 7 ms) are detected for low Er3content, indicating that the Er3−Er3interactions become significant as the Er3content increases. [ABSTRACT FROM AUTHOR]

An atomic force microscopy (AFM) tip has been coated with photoluminescent Eu3+-doped Gd2O3 nanorods using a dielectrophoresis technique, which preserves the red emission of the nanorods (quantum yield 0.47). The performance of the modified tips has been tested by using them for regular topography imaging in tapping and contact modes. Both a regular AFM standard grid and a patterned surface (of an organic-inorganic methacrylate Zr-based oxo-cluster and poly(oxyethylene)/siloxane hybrid) have been used. Similar depth values have been measured using a conventional silicon tip and the nanorod-modified tip. The tips before and after use exhibit similar SEM images and photoluminescence spectra and, thus, seem to be stable under working conditions. These tips should find applications in scanning near-field optical microscopy and other scanning techniques. [ABSTRACT FROM AUTHOR]