Confinement effect of ionic liquid: Improve of the extraction performance of parent metal organic framework for phthalates

Applications of metal organic frameworks in dispersive micro solid phase extraction (D-μ-SPE)

Metal-organic frameworks (MOFs) are a fascinating family of crystalline porous materials made up of metal clusters and organic linkers. In comparison with other porous materials, MOFs have unique characteristics including high surface area, homogeneous open cavities, and permanent high porosity with variable shapes and sizes. For these reasons, MOFs have recently been explored as sorbents in sample preparation by solid-phase extraction (SPE). However, SPE requires large amounts of sorbents and suffers from limited contact surfaces with analytes, which compromises extraction recovery and efficiency. Dispersive SPE (D-SPE) overcomes these limitations by dispersing the sorbents into the sample, which in turn increases contact with the analytes. Miniaturization of the microextraction procedure, particularly the amount of sorbent reduces the amount consumed of the organic solvent and shorten the time required to attain the equilibrium state. This may explain the reported high efficiency and applicability of MOFs in dispersive micro SPE (D-µ-SPE). This method retains all the advantages of solid phase extraction while also being simpler, faster, cheaper, and, in some cases, more effective in comparison with D-SPE. Besides, D-µ-SPE requires smaller amounts of the sorbents which reduces the overall cost, and the amount of waste generated from the analytical process. In this review, we discuss the applications of MOFs in D-µ-SPE of various analytes including pharmaceuticals, pesticides, organic dyes from miscellaneous matrices including water samples, biological samples and food samples.

Ionic liquid-enhanced silica aerogels for the specific extraction and detection of aflatoxin B1 coupled with a smartphone-based colorimetric biosensor

The polymer ionic liquid (1-allyl-3-butylimidazolium bromide) enhanced silica aerogel was modified onto the surface of stainless-steel mesh to immobilize aptamer-1 for the specific recognition of AFB1. The porous channels of silica aerogel could prevent the interference of macromolecules in food samples. Enzyme kinetic analysis showed that the MoS2/Au was an effective peroxidase mimic with a relatively low Michaelis constant (Km) value of 0.17 mM and a high catalytic rate of 3.87 × 10-8 mol (L·s)-1, which exhibited obvious superiority compared with horseradish peroxidase. The established "sandwich-structure" biosensor was coupled with the smartphone "Color Picker" application was used to detect AFB1 with a wide linear range (1-100 ng mL-1) and low detection limit (0.25 ng mL-1). The anti-interference ability of the established biosensor was evaluated by adding different concentrations of standards in corn, peanut, and wheat and matrix effects were 90.84-106.11 %. The results showed that this method demonstrated high specificity, sensitivity, rapidity and low interference in food samples.

Supramolecular Materials as Solid-Phase Microextraction Coatings in Environmental Analysis

Solid-phase microextraction (SPME) has been widely proposed for the extraction, clean-up, and preconcentration of analytes of environmental concern. Enrichment capabilities, preconcentration efficiency, sample throughput, and selectivity in extracting target compounds greatly depend on the materials used as SPME coatings. Supramolecular materials have emerged as promising porous coatings to be used for the extraction of target compounds due to their unique selectivity, three-dimensional framework, flexible design, and possibility to promote the interaction between the analytes and the coating by means of multiple oriented functional groups. The present review will cover the state of the art of the last 5 years related to SPME coatings based on metal organic frameworks (MOFs), covalent organic frameworks (COFs), and supramolecular macrocycles used for environmental applications.

Physicochemical properties and density functional theory calculation of octahedral UiO-66 with Bis(Trifluoromethanesulfonyl)imide ionic liquids

In this study, the physicochemical properties and molecular interactions between zirconium-based metal-organic framework (UiO-66) and three different ionic liquids based on bis(trifluoromethanesulfonyl)imide anion (EMIM+, BMIM+ and OMIM+) was performed via a combined experimental and computational approach. The ionic liquid loaded UiO-66 or IL@UiO-66 was synthesized and characterized to understand the host-guest interaction. Density functional theory calculation was performed to analyse the electronic structure of IL@UiO-66 to provide molecular insight on the dominant interactions occurred in the hybrid material. Results showed that all ILs were successfully incorporated into the micropores of UiO-66. The 3D framework was retained even after loaded with ILs as analyzed from XRD pattern. FTIR spectrum reveals that interactions of ILs with UiO-66 influenced by the alkyl chain length of the cation. The anion has a profound affinity with the UiO-66 due to the presence of electronegative atoms. Phase transition study from DSC suggested that the incorporation of ILs has stabilized the framework of UiO-66 by shifting the endothermic peak to a higher state. These findings were further elaborated with DFT calculation. Geometrical optimizations confirmed the structural parameter changes of UiO-66 when loaded with ILs. These was mainly contributed by the non-covalent interactions which was confirmed by the reduced density gradient scattered plot. Another important findings are the strength of hydrogen bonding at the host-guest interface was influenced by the alkyl chain length. The molecular orbital analysis also shows that the size of alkyl chain influence the reactivity of the hybrid material. The present study provides fundamental insights on the molecular interaction of UiO-66 and ILs as a hybrid material, which can open new possibilities for advanced material for metal-organic framework applications in energy storage system, catalysis, gas storage and medicinal chemistry.