Low-cost Scholl-coupling microporous polymer as an efficient solid-phase microextraction coating for the detection of light aromatic compounds

Length-controlled hydrophobic CF3-COF as a highly efficient absorbent coating for dual-mode solid-phase microextraction of sixteen polycyclic aromatic hydrocarbons in water samples

Polycyclic aromatic hydrocarbons (PAHs), a group of seriously hazardous environmental contaminants, have attracted extensive attention due to their carcinogenicity, genotoxicity, mutagenicity, and ubiquity. In this work, the excellent hydrophobic trifluoromethyl-enriched covalent organic framework (CF3-COF) was designed and synthesized as coating of solid-phase microextraction (SPME). The CF3-COF offered a high adsorption selectivity for PAHs, which could be attributed to the multiple interactions between the CF3-COF and PAHs, including hydrophobicity interaction, π-π and H bond interactions. Furthermore, headspace (HS) and direct immersion (DI) dual-mode solid-phase microextraction (HS/DI-SPME) were innovatively integrated as a dual-mode extraction by varying the length of SPME coating on stainless-steel, which could simultaneously and efficiently extract 16 PAHs with different volatile. Amazingly, the proposed strategy achieved fast adsorption for PAHs and shortened the adsorption equilibrium time to 15 min. By further integrating with gas chromatography tandem mass spectrometry (GC-MS/MS), PAHs could be detected in the range of 0.008-0.16 ng mL-1 with a quantitative limit of 0.029-0.47 ng mL-1, respectively. The recoveries of PAHs in water samples ranged from 80.84 to 117.67 %. This work indicates that the dual-mode CF3-COF-SPME is a promising candidate for the enrichment of multiple hazardous substances in complicated samples.

Tunable Fluorine-Functionalized Scholl-Coupled Microporous Polymer for the Selective Adsorption and Ultrasensitive Analysis of Environmental Liquid-Crystal Monomers

Liquid-crystal monomers (LCMs), especially fluorinated biphenyls and analogues (FBAs), are identified to be an emerging generation of persistent organic pollutants. However, there is a dearth of information about their occurrence and distribution in environmental water and lacustrine soil samples. Herein, a series of fluorine-functionalized Scholl-coupled microporous polymers (FSMP-X, X = 1-3) were designed and synthesized for the highly efficient and selective enrichment of FABs. Their hydrophobicity, porosity, chemical stability, and adsorption performance (capacity, rate, and selectivity) were regulated preciously. The best-performing material (FSMP-2) was employed as the on-line fluorous solid-phase extraction (on-line FSPE) adsorbent owing to its high adsorption capacity (313.68 mg g^-1), fast adsorption rate (1.05 g h^-1), and specific selectivity for FBAs. Notably, an enrichment factor of up to 590.2 was obtained for FSMP-2, outperforming commercial C₁₈ (12.6-fold). Also, the underlying adsorption mechanism was uncovered by density functional theory calculations and experiments. Based on this, a novel and automated on-line FSPE-high-performance liquid chromatography method was developed for ultrasensitive (detection limits: 0.0004-0.0150 ng mL^-1) and low matrix effect (73.79-113.3%) determination of LCMs in lake water and lacustrine soils. This study offers new insight into the highly selective quantification of LCMs and the first evidence for their occurrence and distribution in these environmental samples.

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

In order to better identify the hazards of pollutants, developing the analytical methods that can sensitively detect and precisely monitor the content of trace pollutants has been the constant pursuit. In this paper, a new solid phase microextraction coating-ionic liquid/metal organic framework (IL/MOF) was obtained through the IL-induced strategy and used for the solid phase microextraction (SPME) process. IL was introduced into metal-organic framework (MOF) cage based on the anion of ionic liquid could interact strongly with the zirconium nodes of UiO-66-NH₂. The introduction of IL not only increased the stability of composite, the hydrophobicity of IL also changed the environment of MOF channel, providing the hydrophobic effect to the targets. The confinement effect of IL effectively improved the extraction performance of parent MOF and the extraction performance of synthesized IL/UiO-66-NH₂ for phthalates (PAEs) were 1.3-3.0 times that of parent UiO-66-NH₂. Thanks to the strong interaction force (hydrogen bonding interaction, π-π stacking, hydrophobic interaction force), the IL/UiO-66-NH₂-coated fiber coupled with gas chromatography-mass spectrometer showed a wide linear ranges (1-5000 ng L^-1) with good correlation (R², 0.9855-0.9987), lower detection limit (0.2-0.4 ng L^-1) and satisfactory recoveries (95.3-119.3%) for PAEs. This article is dedicated to provide another way to improve the extraction performance of material.

The mechanochemical synthesis of polymers

Mechanochemistry - the utilization of mechanical forces to induce chemical reactions - is a rarely considered tool for polymer synthesis. It offers numerous advantages such as reduced solvent consumption, accessibility of novel structures, and the avoidance of problems posed by low monomer solubility and fast precipitation. Consequently, the development of new high-performance materials based on mechanochemically synthesised polymers has drawn much interest, particularly from the perspective of green chemistry. This review covers the constructive mechanochemical synthesis of polymers, starting from early examples and progressing to the current state of the art while emphasising linear and porous polymers as well as post-polymerisation modifications.

Fabrication of an SPME fiber based on ZnO@GA nanorods coated onto fused silica as a highly efficient absorbent for the analysis of cancer VOCs in water and urine

Analysis of volatile organic compounds (VOCs) secreted in urine, blood, breath, etc. is a new method for monitoring the metabolism and biochemistry of the human body. However, due to the complexity of samples, a pre-concentration step is necessary before the final analysis with gas chromatography-mass spectroscopy (GC-MS). Therefore, miniaturized extraction methods such as solid-phase microextraction (SPME) can be a promising and simple pre-concentration technique. Different strategies have been adopted for the fabrication or modification of SPME fibers. This study presents the preparation and characterization of glass optical fibers coated with ZnO nanorods functionalized with gallic acid (ZnO@GA nanorod) as SPME adsorbent in GC-MS. ZnO@GA nanorods were synthesized separately and then coated onto the fibers. The coated fibers were characterized by using field emission scanning electron microscopy coupled with energy dispersive analysis of X-rays (FESEM/EDAX) and Fourier transform infrared spectroscopy (FTIR) techniques. Possessing a high surface to volume ratio of ZnO nanorods and functional groups of GA, the ZnO@GA nanorod-based SPME fibers exhibited good extraction performance for VOCs comparing with the commercial polydimethylsiloxane (PDMS) coated fibers. Under optimal conditions (NaCl concentration, 30% w/v; extraction time of 25 min; pH, 5-7 and stirring rate of 400 rpm) ZnO@GA nanorods coated fibers achieved low detection limits (0.32-4.8 μg/L), low quantification limits (1.8-16.3 μg/L) and good linearity (5-1000 μg/L) for selected VOCs. The repeatability (n = 3) for a single fiber was within the range of 4.1-7.9% (intra-day) and 5.7-9.6% (inter-day) while the reproducibility (n = 3) of fiber-to-fiber were in the range of 4.7% and 9.9%. This method was successfully used for the determination of six VOCs in water and urine with satisfactory recoveries of 90-112%. ZnO@GA nanorod coated fibers, despite possessing a much thinner coating compared to the commercial fibers, revealed a better overall extraction efficiency towards VOCs. These results indicated that the ZnO@GA provided a promising alternative in sample pretreatment and analysis in GC-MS.

Immobilization of a Pd(ii)-containing N-heterocyclic carbene ligand on porous organic polymers: efficient and recyclable catalysts for Suzuki–Miyaura reactions

Two NHC–Pd(ii) complexes immobilized on porous organic polymers were successfully prepared via Scholl reactions and metallization. These complexes were applied in Suzuki–Miyaura reaction as heterogeneous catalysts with excellent yield and TON.

The mechanochemical Scholl reaction as a versatile synthesis tool for the solvent-free generation of microporous polymers

Herein we report the mechanochemical Scholl polymerization of 1,3,5-triphenylbenzene in a high speed ball mill. The reaction is conducted solvent-free, solely using solid FeCl3. The resulting porous polymer was obtained in >99% yield after very short reaction times of only 5 minutes and exhibits a high specific surface area of 658 m2 g-1, which could be further enhanced up to 990 m2 g-1 by liquid assisted grinding. Within this study we illuminate the origin of porosity by investigating the impact of various milling parameters and milling materials, temperature and pressure, and different liquids for LAG as well as post polymer milling. Finally we expand the procedure to different monomers and mills, to present the mechanochemical Scholl reaction as a versatile synthesis tool for porous polymers.

Amino-modified Scholl-coupling mesoporous polymer for online solid-phase extraction of plant growth regulators from bean sprouts

A new amino-modified Scholl-coupling mesoporous polymer (NH₂@SMPA)-online solid-phase extraction method, coupled with high-performance liquid chromatography (online SPE-HPLC) was established for the analysis of six plant growth regulators (PGRs) in bean sprouts. NH₂@SMPA was synthesized by acid-catalyzed deacetylation of acetylamino-Scholl-coupling mesoporous polymer (SMPA). The diversity of functional groups, such as aromatic, acetylamino, and NH₂, was conducive to multiple binding interactions between NH₂@SMPA and PGRs. NH₂@SMPA exhibited superior extraction capability for PGRs, compared with SMPA and commercial adsorbents. The extraction conditions, including loading solvent, pH of loading solution, eluting solvent, and flow rates of loading and elution, were optimized. Under the optimized conditions, wide linear ranges (0.01-500 μg kg^-1) and low detection limits (2.34-20.2 ng kg^-1) were obtained. The recoveries were satisfactory, i.e., 86.0% to 109% with relative standard deviations ≤9.8% (n = 3). Finally, the online SPE-HPLC method was successfully used for determination of PGRs in bean sprouts.

Conjugated porous polymers: incredibly versatile materials with far-reaching applications

This review discusses conjugated porous polymers and focuses on relating design principles and synthetic methods to key properties and applications such as (photo)catalysis, gas storage, chemical sensing, energy storage and environmental remediation.

Recent Applications and Newly Developed Strategies of Solid-Phase Microextraction in Contaminant Analysis: Through the Environment to Humans

The present review aims to describe the recent and most impactful applications in pollutant analysis using solid-phase microextraction (SPME) technology in environmental, food, and bio-clinical analysis. The covered papers were published in the last 5 years (2014–2019) thus providing the reader with information about the current state-of-the-art and the future potential directions of the research in pollutant monitoring using SPME. To this end, we revised the studies focused on the investigation of persistent organic pollutants (POPs), pesticides, and emerging pollutants (EPs) including personal care products (PPCPs), in different environmental, food, and bio-clinical matrices. We especially emphasized the role that SPME is having in contaminant surveys following the path that goes from the environment to humans passing through the food web. Besides, this review covers the last technological developments encompassing the use of novel extraction coatings (e.g., metal-organic frameworks, covalent organic frameworks, PDMS-overcoated fiber), geometries (e.g., Arrow-SPME, multiple monolithic fiber-SPME), approaches (e.g., vacuum and cold fiber SPME), and on-site devices. The applications of SPME hyphenated with ambient mass spectrometry have also been described.

Core-Shell Metal-Organic Frameworks as the Mixed-Mode Stationary Phase for Hydrophilic Interaction/Reversed-Phase Chromatography

Stationary phases with mixed-mode mechanisms have emerged as a hot research topic. In the present research, monodisperse core-shell UiO-67@SiO₂ materials were prepared and further served as the packed column for mixed-mode hydrophilic interaction liquid chromatography/reversed-phase liquid chromatography. The developed UiO-67@SiO₂ materials were characterized via thermogravimetric analysis, scanning electron microscopy, X-ray Powder diffraction, and Fourier transform infrared techniques. The developed UiO-67@SiO₂ column shows flexible selectivity for separation of both hydrophobic (anilines, alkylbenzenes, and polycyclic aromatic hydrocarbons) and hydrophilic (thioureas) compounds. Furthermore, the UiO-67@SiO₂ column was also utilized to characterize potential pollutants in lake water samples. In summary, the UiO-67@SiO₂ column provided flexible selectivity and wide-range retention behaviors for both hydrophilic and hydrophobic analytes.

Double -shelled hollow ZnO/carbon nanocubes as an efficient solid-phase microextraction coating for the extraction of broad-spectrum pollutants

Efficient extraction of pollutants with different chemical properties from environmental samples has attracted great attention in the development of analytical chemistry. However, it is still a challenge to develop an appropriate and sensitive adsorbent for determining broad-spectrum analytes. Herein, zeolitic imidazole framework-8 (ZIF-8)-derived double-shelled hollow zinc oxide/carbon (ZnO/C) nanocubes were reported as a novel coating for solid-phase microextraction (SPME). The nanocubes with a unique structure and composition were obtained by controlled etching of ZIF-8 with tannic acid (TA) followed by pyrolysis. When a ZnO/C nanocube-coated fiber (ZnO/C-F) was used to extract the complex environmental samples containing both nonpolar (benzene compounds (BTEX)) and polar (chlorophenols (CPs)) pollutants, excellent extraction performance was achieved; we obtained low detection limits (0.14-0.56 ng L-1 for BTEX and 1.10-2.84 ng L-1 for CPs), good repeatability (2.2-5.9% for six replicated extractions) and excellent reproducibility (0.61-7.8%, fiber to fiber). The broad-spectrum SPME performance was ascribed to the synergistic effect between the composition and structure of ZnO/C nanocubes. Compositionally, the uniform dispersion of ZnO and carbon framework could provide abundant adsorption active sites, where Zn-OHs bound CPs by hydrogen bonding and carbon absorbed BTEX through π-π stacking interaction and hydrophobic interaction. Structurally, the double-shelled hollow morphology of the nanocubes was favorable for the sensitive extraction. Finally, the established ZnO/C-F-based headspace-SPME method was used for the preconcentration and determination of abundant analytes from real water samples. These findings open the door for the practical use of double-shelled hollow multicompositional inorganic materials.