[BMIM][X] Ionic Liquids Supported on a Pillared-Layered Metal-Organic Framework: Synthesis, Characterization, and Adsorption Properties.

Combining ionic liquids (ILs) and metal-organic frameworks (MOFs) can be an intriguing opportunity to develop advanced materials with different adsorption capabilities for environmental applications. This study reports the preparation and characterization of a 3D pillared-layered compound, namely, [Zn2(tz)2(bdc)] (CIM91), formed by 1,2,4-triazole (Htz) and 1,4-benzenedicarboxylic acid (H2bdc) ligands. Then, various loadings of the water-stable and hydrophobic IL, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and the water-soluble 1-n-butyl-3-methylimidazolium chloride ([BMIM][Cl]) were incorporated into CIM91. Detailed characterization by X-ray powder diffraction (XRD), FT-IR spectra, scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) analysis, N2 adsorption measurements, and thermogravimetric analysis confirmed the formation of [BMIM][X]/CIM91 composites and the structural stability of the MOF after the incorporation of the ionic liquids. CO2 adsorption-desorption analysis was experimentally carried out for all the materials at 298 K and 318 K, demonstrating a great enhancement in the CO2 adsorption properties of the sole MOF CIM91, particularly by including [BMIM][PF6] species in its structure with a double isosteric heat of CO2 adsorption. The composites were also tested for the adsorption of methylene blue (MB) dye. The results indicate that the incorporation of [BMIM][X] into CIM91 can substantially modify the adsorption properties of the MOF. The influence of the nature of the [BMIM][X] anions on these properties has also been analyzed.

Mixed Functionalization of Organic Ligands in UiO-66: A Tool to Design Metal-Organic Frameworks for Tailored Microextraction.

The mixed-ligand strategy was selected as an approach to tailor a metal-organic framework (MOF) with microextraction purposes. The strategy led to the synthesis of up to twelve UiO-66-based MOFs with different amounts of functionalized terephthalate ligands (H-bdc), including nitro (-NO2) and amino (-NH2) groups (NO2-bdc and NH2-bdc, respectively). Increases of 25% in ligands were used in each case, and different pore environments were thus obtained in the resulting crystals. Characterization of MOFs includes powder X-ray diffraction, infrared spectroscopy, and elemental analysis. The obtained MOFs with different degrees and natures of functionalization were tested as sorbents in a dispersive miniaturized solid-phase extraction (D-µSPE) method in combination with high-performance liquid chromatography (HPLC) and diode array detection (DAD), to evaluate the influence of mixed functionalization of the MOF on the analytical performance of the entire microextraction method. Eight organic pollutants of different natures were studied, using a concentration level of 5 µg· L-1 to mimic contaminated waters. Target pollutants included carbamazepine, 4-cumylphenol, benzophenone-3, 4-tert-octylphenol, 4-octylphenol, chrysene, indeno(1,2,3-cd)pyrene, and triclosan, as representatives of drugs, phenols, polycyclic aromatic hydrocarbons, and disinfectants. Structurally, they differ in size and some of them present polar groups able to form H-bond interactions, either as donors (-NH2) or acceptors (-NO2), permitting us to evaluate possible interactions between MOF pore functionalities and analytes' groups. As a result, extraction efficiencies can reach values of up to 60%, despite employing a microextraction approach, with four main trends of behavior being observed, depending on the analyte and the MOF.

Application of a Pillared-Layer Zn-Triazolate Metal-Organic Framework in the Dispersive Miniaturized Solid-Phase Extraction of Personal Care Products from Wastewater Samples.

The pillared-layer Zn-triazolate metal-organic framework (CIM-81) was synthesized, characterized, and used for the first time as a sorbent in a dispersive micro-solid phase extraction method. The method involves the determination of a variety of personal care products in wastewaters, including four preservatives, four UV-filters, and one disinfectant, in combination with ultra-high performance liquid chromatography and UV detection. The CIM-81 MOF, constructed with an interesting mixed-ligand synthetic strategy, demonstrated a better extraction performance than other widely used MOFs in D-µSPE such as UiO-66, HKUST-1, and MIL-53(Al). The optimization of the method included a screening design followed by a Doehlert design. Optimum conditions required 10 mg of CIM-81 MOF in 10 mL of the aqueous sample at a pH of 5, 1 min of agitation by vortex and 3 min of centrifugation in the extraction step; and 1.2 mL of methanol and 4 min of vortex in the desorption step, followed by filtration, evaporation and reconstitution with 100 µL of the initial chromatographic mobile phase. The entire D-µSPE-UHPLC-UV method presented limits of detection down to 0.5 ng·mL-1; intra-day and inter-day precision values for the lowest concentration level (15 ng·mL-1)-as a relative standard deviation (in %)-lower than 8.7 and 13%, respectively; average relative recovery values of 115%; and enrichment factors ranging from ~3.6 to ~34. The reuse of the CIM-81 material was assessed not only in terms of maintaining the analytical performance but also in terms of its crystalline stability.

Influence of Ligand Functionalization of UiO-66-Based Metal-Organic Frameworks When Used as Sorbents in Dispersive Solid-Phase Analytical Microextraction for Different Aqueous Organic Pollutants.

Four metal-organic frameworks (MOFs), specifically UiO-66, UiO-66-NH2, UiO-66-NO2, and MIL-53(Al), were synthesized, characterized, and used as sorbents in a dispersive micro-solid phase extraction (D-µSPE) method for the determination of nine pollutants of different nature, including drugs, phenols, polycyclic aromatic hydrocarbons, and personal care products in environmental waters. The D-µSPE method, using these MOFs as sorbents and in combination with high-performance liquid chromatography (HPLC) and diode-array detection (DAD), was optimized. The optimization study pointed out to UiO-66-NO2 as the best MOF to use in the multi-component determination. Furthermore, the utilization of isoreticular MOFs based on UiO-66 with the same topology but different functional groups, and MIL-53(Al) to compare with, allowed us for the first time to evaluate the influence of such functionalization of the ligand with regards to the efficiency of the D-µSPE-HPLC-DAD method. Optimum conditions included: 20 mg of UiO-66-NO2 MOF in 20 mL of the aqueous sample, 3 min of agitation by vortex and 5 min of centrifugation, followed by the use of only 500 µL of acetonitrile as desorption solvent (once the MOF containing analytes was separated), 5 min of vortex and 5 min of centrifugation. The validation of the D-µSPE-HPLC-DAD method showed limits of detection down to 1.5 ng·L-1, average relative recoveries of 107% for a spiked level of 1.50 µg·L-1, and inter-day precision values with relative standard deviations lower than 14%, for the group of pollutants considered.

Homo- and heteronuclear compounds with a symmetrical bis-hydrazone ligand: synthesis, structural studies, and luminescent properties.

Nine new coordination compounds have been synthesized by the reaction of salts of bivalent metal ions (a=Zn(II) , b=Cu(II) , c=Ni(II) , d=Co(II) ) with the bis(benzoylhydrazone) derivative of 4,6-diacetylresorcinol (H4 L). Three kinds of complexes have been obtained: homodinuclear compounds [M2 (H2 L)2 ]⋅nH2 O (1 a, 1 b, 1 c, and 1 d), homotetranuclear compounds [M4 (L)2 ]⋅n(solv) (2 a and 2 c), and heterotetranuclear compounds [Zn2 M2 (L)2 ]⋅n(solv) (2 ab, 2 ac, and 2 ad). The structures of the free ligand H4 L⋅2 DMSO and its complexes [Zn2 (H2 L)2 (DMSO)2 ] (1 a*), [Zn4 (L)2 (DMSO)6 ] (2 a*), and [Zn0.45 Cu3.55 (L)2 (DMSO)6 ]⋅2 DMSO (2 ab*) were elucidated by single-crystal X-ray diffraction. The ligand shows luminescence properties and its fluorimetric behavior towards M(II) metals (M=Zn, Cu, Ni and Co) has been studied. Furthermore, the solid-state luminescence properties of the ligand and compounds have been determined at room temperature. (1) H NMR spectroscopic monitoring of the reaction of H4 L with Zn(II) showed the deprotonation sequence of the OH/NH groups upon metal coordination. Heteronuclear reactions have also been monitored by using ESI-MS and spectrofluorimetric techniques.

An infrastructure to enable lightweight context-awareness for mobile users.

Mobile phones enable us to carry out a wider range of tasks every day, and as a result they have become more ubiquitous than ever. However, they are still more limited in terms of processing power and interaction capabilities than traditional computers, and the often distracting and time-constricted scenarios in which we use them do not help in alleviating these limitations. Context-awareness is a valuable technique to address these issues, as it enables to adapt application behaviour to each situation. In this paper we present a context management infrastructure for mobile environments, aimed at controlling context information life-cycle in this kind of scenarios, with the main goal of enabling application and services to adapt their behaviour to better meet end-user needs. This infrastructure relies on semantic technologies and open standards to improve interoperability, and is based on a central element, the context manager. This element acts as a central context repository and takes most of the computational burden derived from dealing with this kind of information, thus relieving from these tasks to more resource-scarce devices in the system.

From Cu(I) and Cu(I)-Cu(II) mixed-valence clusters to 2D Cu(II) and Cu(I) coordination polymers supported by a flexible bis-tetrazole organosulfur ligand.

Three coordination compounds from the reaction of copper(II) bromide with the flexible bis-tetrazole organosulfur ligand, 1,2-bis(1-methyl-1H-tetrazole-5-ylthio)ethane (bmtte) have been isolated and characterised. The identification of polymeric 2∞Cu2Br4(bmtte) (1), trinuclear [Cu3Br4(bmtte)2] (2) and tetranuclear [Cu2Br2(bmtte)]2 (3) compounds shows that the reaction conditions have a significant influence on the structure of the complexes formed. Moreover, two polymorphs of the 2D Cu(II)-coordination polymer 1 have been isolated and these crystallise in the monoclinic C2/m (1m) and the triclinic P1̄ (1t) space groups. The thermal stabilities and behaviour in aqueous media of compounds 1-3 were investigated along with the reactivity of compound 2 with CuBr2 and KI. The solid-state reaction between mixed-valence compound 2 with KI or the direct reaction of CuI and bmtte under microwave irradiation allowed the preparation of the polymeric 2∞Cu4I4(bmtte)2 (4). The redox behaviour of complexes 2 and 3 was analysed by cyclic voltammetry.

Insights into Paraben Adsorption by Metal-Organic Frameworks for Analytical Applications.

Metal-organic frameworks (MOFs) are attractive materials used as sorbents in analytical microextraction applications for contaminants of emerging concern (CECs) from environmental liquid matrices. The demanding specs for a sorbent in the analytical application can be comprehensively studied by considering the interactions of the target analytes with the frameworks by the use of single-crystal X-ray diffraction, computational analysis, and adsorption studies, including the kinetic ones. The current study intends a better understanding of the interactions of target CECs (particularly, propylparaben (PPB) as a model) and three Zn-based layered pillared MOFs: CIM-81 [Zn2(tz)2(bdc)] (Htz = 1,2,4-triazole and H2bdc = 1,4-benzenedicarboxylic acid) and their amino derivatives [Zn2(NH2-tz)2(bdc)] CIM-82 and [Zn2(tz)2(NH2-bdc)] CIM-83 (NH2-Htz = 3-amino-1,2,4-triazole and NH2-H2bdc = 2-amino-1,4-benzenedicarboxylic acid). The crystal structures of the two solvate compounds (dma@CIM-81 (dma = dimethylacetamide) and acetone@CIM-81) were solved by single-crystal X-ray diffraction to determine the points of interaction between the framework and the guest molecules. They also served as a starting point for the computational modeling of the PPB@CIM-81 compound, showing that up to two PPB molecules can be hosted in one of the pores, while only one can be trapped in the second pore type, leading to a maximum theoretical capacity of 291.9 mg g-1. This value is close to the value obtained by the adsorption isotherm experiment for CIM-81 (283 mg g-1). This value is, by far, higher than those previously reported for other materials for the removal of PPB from water, and also higher than the experimental values obtained for CIM-82 (54 mg g-1) and CIM-83 (153 mg g-1). The kinetics of adsorption is not very fast, with uptake of about 40% in 3 h, although a 70% release in methanol is achieved in 1 h. In addition, a further comparison of performance in analytical microextraction (requiring only 10 mg of CIM-81) was carried out together with chromatographic analysis to support all insights attained, with the method being able to monitor CECs as low as µg L-1 levels in complex environmental water samples, thus performing successfully for water monitoring even in multicomponent scenarios.