Four microporous lanthanide metal-organic frameworks (MOFs), namely Ln(BTC)(H2O)(DMF)1.1 (Ln = Tb, Dy, Er and Yb, DMF = dimethylformamide, H3BTC = benzene-1,3,5-tricarboxylic acid), have been used for selective adsorption of Pb(ii) and Cu(ii). Among these MOFs, the Dy-based MOF shows better adsorption property and selectivity toward Pb(ii) and Cu(ii) ions. Adsorption isotherms indicate that sorption of Pb(ii) and Cu(ii) on MOFs is via monolayer coverage. Preconcentration is based on solid-phase extraction in which MOFs were rapidly injected into water samples and adsorption of metal ions was rapid because of good contact with analyte; then adsorbed Pb(ii) and Cu(ii) ions were analyzed by FAAS. The optimized methodology represents good linearity between 1 and 120 μg L(-1) and detection limit of 0.4 and 0.26 μg L(-1) for Pb(ii) and Cu(ii), respectively. Subsequently the method was evaluated for preconcentration of target metal ions in some environmental water samples.

Here we report the use of a pillaring strategy for the design and synthesis of three novel amidefunctionalized metal-organic frameworks (MOFs), TMUs-22/-23/-24, isoreticular to the recently reported iminefunctionalized TMU-6 and TMU-21 MOFs. An extensive study of their CO2 sorption properties and selectivity for CO2 over N2, from single gas sorption isotherms to breakthrough measurements, revealed that not only the incorporation of amide groups but also their accessibility is crucial to obtain enhanced CO2 sorption and CO2/N2 selectivity. Therefore, the MOF with more accessible amide groups (TMU-24) shows a CO2/N2 selectivity value of ca. 10 (as revealed by breakthrough experiments), which is ca. 500 % and 700 % of the selectivity values observed for the other amidecontaining (TMU-22 and TMU-23) and imine-containing (TMU-6 and TMU-21) MOFs. ASSOCIATED CONTENT Supporting Information. Synthetic procedure for ligand synthesis, crystallographic data, PXRD diagrams, TGA plots, gas sorption and separation data. This material is available free of charge via the Internet at http://pubs.acs.org.

In this study, N-(3-halophenyl)-2-pyrazinecarboxamide ligands, L(3-F), L(3-Cl), L(3-Br), and L(3-I), carrying a different halogen atom on the phenyl meta-position and N-phenyl-2-pyrazinecarboxamide ligand, L(H), have been employed for the synthesis of 12 mercury(II) complexes, [HgCl2(L(H))]n, 1, [HgCl2(L(3-Cl))]n, 2, [Hg2Cl4(L(3-Br))2], 3, [Hg2Cl4(L(3-I))2], 4, [Hg2Br4(L(H))2], 5, [HgBr2(L(3-F))], 6, [HgBr2(L(3-Cl))], 7, [HgBr2(L(3-Br))], 8, [HgBr2(L(3-I))], 9, [Hg2I4(L(H))2], 10, [HgI2(L(3-Br))], 11, and [HgI2(L(3-I))]n, 12. Interestingly, structural analysis clearly shows that, by the replacing of coordinated anions from chloride with bromide and iodide in each series containing the same ligand, the coordination geometry and structural motif of the resulting compounds have been dramatically affected. One of the common features in the crystal structures of these complexes is that there is a strong tendency to form halogen bonding synthons between adjacent halophenyl and pyrazine rings. The influence of these halogen bonding interactions on the supramolecular assemblies has been discussed with the help of geometrical analysis and theoretical calculations. The X···N halogen bonding distances are 2.5-9.4% shorter than the sum of the van der Waals radii of nitrogen and halogen atoms. Theoretical methods also show the halogen bonding energies within a range of -27.86 to -46.15 kJ·mol(-1). In all complexes synthesized here, the pyrazine ring is coordinated to the mercury(II) ion through the N atom syn to the carbonyl. Therefore, the second common feature of the crystal structures for complexes studied here is the selectivity of the metal ion coordination site. The halogen bond synthon repetitivity across these compounds and selectivity in the mercury(II) ion coordination site further point to application in the coordination crystal engineering research field.

Two novel pillared metal-organic frameworks (MOFs) including urea-functional groups are introduced. Herein, urea functional groups were incorporated into the MOF backbone by preparing urea-ditopic ligand. These frameworks (TMU-18 and TMU-19) were fabricated using the synthesized urea-containing ligand, 4,4'-Bipyridine (bpy) and 1,2-Bis(4-pyridyl)ethane (bpe), respectively using zinc nitrate as metal source. Subsequently, TMU-18 and TMU-19 were characterized by X-ray diffraction, IR spectroscopy, elemental analysis, scanning electron microscopy (SEM) and thermogravimetric analysis. Furthermore, their potential talent as organocatalysts was evaluated in the regioselective methanolysis of epoxides. 4 (urea-based ligand) is 4,4'-(carbonylbis(azanediyl))dibenzoic acid, bipy and bpe are 4,4'bipyridine and 1,2-bis(4-pyridyl)ethane, respectively, Figure 1. Experimental Section Apparatus and ReagentsAll starting materials, including 1,1'-Carbonyldiimidazole, 4-Aminobenzoic acid were purchased from commercial suppliers (Sigma-Aldrich, Merck) and used as received. The infrared spectra were recorded on a Nicolet Fourier Transform IR, Nicolet 100 spectrometer in the range 500-4000 cm -1 using the KBr disk technique. Elemental analyses (carbon, hydrogen, and nitrogen) were performed using an ECS 4010 CHN made in Costech, Italy. Melting points were obtained by a Bamstead Electrothermal type 9200 melting point apparatus and corrected.Thermogravimetric analyses (TGA) of the compounds were performed on a computer-controlled PL-STA 1500 apparatus. The 1 H-NMR spectrum was recorded on a Bruker AC-250 MHz spectrometer at ambient temperature in d 6 -DMSO and CDCl 3 . X-ray powder diffraction (XRPD) measurements were performed using a Philips Xpert diffractometer with monochromated Cu-Kα radiation (λ = 1.54056 Å). The samples were also characterized by field emission scanning electron microscope (FE-SEM) SIGMA ZEISS and TESCAN MIRA (Czech) with gold coating. Single-Crystal Diffraction.X-ray crystal structure determinations: Crystals in viscous paraffin oil were mounted on cryoloops and intensity data were collected on the Australian Synchrotron MX1 beamline at 100 K with wavelength (λ = 0.71073 Å). The data were collected using the BlueIce 24 GUI and processed with the XDS 25 software package. The structures were solved by conventional methods and refined by full-matrix least-squares on all F 2 data using SHELX97 26 or SHELX2014

Urea groups are known to form strong hydrogen bonds with molecules containing atom(s) that can act as hydrogen bond acceptor(s). Thus, urea is a particularly interesting building block for designing receptors for neutral or charged guests. In the quest for new sensors with enhanced performance for the detection of nitro-substituted compounds, two pillared metal-organic frameworks containing urea functional groups were synthesized and structurally characterized. The sensing properties of these frameworks toward nitro-analytes were investigated and compared to each other. The study clearly reveals the importance of urea groups orientation inside the pore cavity of MOFs, as well as the supramolecular interactions between the interpenetrated networks. This work is interesting as it represents the first example of urea-functionalized MOFs for nitro-analytes recognition.

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