Covalent organic framework-graphene oxide composite: A superior adsorption material for solid phase microextraction of bisphenol A

Preparation and evaluation of Fe3O4@C@NiCo-LDH@CDs composites for magnetic solid-phase extraction of trace endocrine disruptors

The widespread use of endocrine disruptors (EDPs) has certain potential hazards to organisms and environments, and it is particularly important to develop effective pretreatment methods before detection of EDPs in complex samples. In this work, a novel magnetic nanocomposite decorated with layered double hydroxides (LDHs) and carbon dots (CDs) was designed and prepared for magnetic solid-phase extraction (MSPE) of EDPs (bisphenol S, bisphenol F, bisphenol A, bisphenol AF, diethylstilbestrol and 4-cumylphenol) combined with high-performance liquid chromatography-ultraviolet (HPLC-UV) detection. The prepared composites were characterized by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the adsorption mechanism towards these EDPs might be mainly based on hydrogen bonds and π-π conjugation. Under the optimized conditions, the proposed method showed limits of detection within 0.05-0.50 μg L-1 and limits of quantitation within 0.2-2.0 μg L-1, and good linearity (R2 ≥ 0.9975) was presented in the range of 0.2-200 μg L-1. Finally, the Fe3O4@C@NiCo-LDH@CDs composite-based MSPE-HPLC-UV method was applied for enrichment and determination of EDPs in water, milk, and tea beverage samples with recoveries in the range of 81.2-119.8% and relative standard deviations below 9.7%.

The synthesis strategies of covalent organic frameworks and advances in their application for adsorption of heavy metal and radionuclide

Covalent organic frameworks (COFs) are a novel type of porous materials, with unique properties, such as large specific surface areas, high porosity, pronounced crystallinity, tunable pore sizes, and easy functionalization, and thus have received considerable attention in recent years. COFs play an essential role in the catalytic degradation, adsorption, and separation of heavy metals, radionuclides. In recent years, considering several outstanding characteristics of COFs, including their good thermal/chemical stability, high crystallinity, and remarkable adsorption capacity, they have been widely used in the removal of various environment pollutants. This review primarily discusses the synthesis strategies of COFs along with their diverse synthesis methods, and provides a comprehensive summary and analysis of recent research advances in the use of COFs for removing heavy metal ions and radionuclides from water bodies. Additionally, the adsorption mechanism of COFs with regard to metal ions was determined by analyzing the structural characteristics of COFs. Finally, the future research directions on COFs adsorb rare earth element was discussed.

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.

Stacked Covalent Organic Ribbons Perpendicular to Graphene Oxide Sheets; a 1D-p-2D Design for Photocatalytic Tandem Reactions

Development of one dimensional covalent organic frameworks (1D-COFs) with potential in light absorption and catalysis is still challenging, due to their rapid interpenetration to form 2D and 3D porous structures. Here we report a successful synthesis of imine-linked 1D covalent organic ribbons (COR), using two simple linear building blocks 1,4-Benzenediamine (Bda) and [2,2'-Bipyridine]-5,5'-dicarbaldehyde (Bpy). The obtained 1D structure with nanorod morphology could keep its physicochemical characteristic properties when it is perpendicular to the surface of graphene oxide (GO) sheets (1D-p-2D structure). Due to an AB π- π stacking and efficient charge transfer between perpendicular 1D COR and GO sheets, the obtained nanocomposite showed strong visible light absorbance (400-700 nm) with coefficient of 4.400 M-1  cm-1 and decreased recombination rate of photogenerated reactive species by 92 %. The strategy of 1D-p-2D light driven system greatly enhanced the photocatalytic activity in practical applications such as both oxidation and hydrogenation tandem reactions to a rate constant of higher than 0.02 min-1 . This study presents the first case of 1D covalent organic polymers grown perpendicularly on a carbon-based layer for boosting electron mobility through the junction between the two components.

Recent progress in the synthesis and applications of covalent organic framework-based composites

Covalent organic frameworks (COFs) have historically been of interest to researchers in different areas due to their distinctive characteristics, including well-ordered pores, large specific surface area, and structural tunability. In the past few years, as COF synthesis techniques developed, COF-based composites fabricated by integrating COFs and other functional materials including various kinds of metal or metal oxide nanoparticles, ionic liquids, metal-organic frameworks, silica, polymers, enzymes and carbon nanomaterials have emerged as a novel kind of porous hybrid material. Herein, we first provide a thorough summary of advanced strategies for preparing COF-based composites; then, the emerging applications of COF-based composites in diverse fields due to their synergistic effects are systematically highlighted, including analytical chemistry (sensing, extraction, membrane separation, and chromatographic separation) and catalysis. Finally, the current challenges associated with future perspectives of COF-based composites are also briefly discussed to inspire the advancement of more COF-based composites with excellent properties.

Recent progress of covalent organic frameworks as attractive materials for solid-phase microextraction: A review

Solid-phase microextraction (SPME) is a green, environmentally friendly, and efficient technique for sample pre-treatment. Covalent organic frameworks (COFs), a class of porous materials formed by covalent bonds, have gained prominence owing to their remarkable attributes, including large specific surface area, tunable pore size, and robust thermal/chemical stability. These characteristics have made COFs highly appealing as potential coatings for SPME fiber over the past decades. In this review, various methods used to prepare SPME coatings based on COFs are presented. These methods encompass physical adhesion, sol-gel processes, in situ growth, and chemical cross-linking strategies. In addition, the applications of COF-based SPME coating fibers for the preconcentration of various targets in environmental, food, and biological samples are summarized. Moreover, not only their advantages but also the challenges they pose in practical applications are highlighted. By shedding light on these aspects, this review aims to contribute to the continued development and utilization of COF materials in the field of sample pretreatment.

Efficient decontamination of organic pollutants from wastewater by covalent organic framework-based materials

Covalent organic frameworks (COFs), assembling through covalent bonds, are a rising class of porous materials. Nowadays, various COFs are widely applied in organic pollutants decontamination due to the outstanding capabilities of large surface area, multiple functional groups, porous structure, excellent absorptivity, flexible design and so on. This review concentrates on the applications of COFs in different decontamination technologies such as solid-phase extraction, membrane filtration and sieving, adsorption, and catalysis reaction. The factors influencing water chemistry, such as pH, temperature, salt concentration and natural organic matter, are summarized in terms of their impact on decontamination performance and the extraction mechanisms for the diverse analytes. The interaction mechanisms between COFs and organic pollutants were hydrogen bonding, π-π stacking, hydrophilic, hydrophobic, and electrostatic interactions. Furthermore, a perspective on current obstacles and upcoming developments of COFs for organic pollutant removal has been provided. Due to their adaptable and versatile design as well as elaborate and diverse functionalization, COFs possess significant possibility in ameliorating environmental pollution.

Construction of a Biomimetic Receptor Based on Hydrophilic Multifunctional Monomer Covalent Organic Framework Molecularly Imprinted Polymers for Molecular Recognition of Cyanidin-3-O-Glucoside

Anthocyanins (AOCs) are phenols that are readily soluble in water and are commonly present in plants. The chemical instability of AOC, however, causes it to be severely limited in terms of extraction and purification. Hence, in order to obtain efficient and stable extraction of AOC, we designed hydrophilic multifunctional monomer covalent organic framework molecularly imprinted polymers (HMCMIPs) as adsorbents. The functional reagent, p-aminobenzenesulfonic acid (ASA), was added to this material during synthesis to facilitate the sulfonation modification of covalent organic frameworks (COFs), which enhanced its affinity for hydrophilic guests (cyanidin-3-O-glucoside, the representative nutritional and functional ingredient in AOC). With ASA serving as a terminator, overextension of the material to form micron-level cross-linked structures is prevented, thereby increasing its surface area and mass transfer efficiency. The biomimetic receptors were then created by integrating MIPs into sulfonated COFs in order to create multiple binding sites specific for C3G recognition. HMCMIPs exhibited excellent adsorption capacity (1566 mg/g) and superior selectivity (selectivity coefficient >12) for C3G. It has been demonstrated that high purity (93.72%) C3G can be obtained rapidly and efficiently by utilizing HMCMIPs. There may be a potential benefit to the synthesis strategy of HMCMIPs for the extraction of specific active ingredients in the future.

Adsorption Performance of Magnetic Covalent Organic Framework Composites for Bisphenol A and Ibuprofen

As typical environmental endocrine disruptors and nonsteroidal anti-inflammatory drugs, bisphenol A and ibuprofen in water supplies can cause great harm to the ecological environment and human health. In this study, magnetic covalent organic framework composites Fe₃O₄@COF-300 were synthesized by the hydrothermal method and used to remove bisphenol A and ibuprofen from water. Fe₃O₄@COF-300 could be rapidly separated from the matrix by external magnetic fields, and could selectively adsorb bisphenol A and ibuprofen in the presence of coexisting compounds such as phenol, Congo red, and amino black 10B. The removal efficiency of ibuprofen was 96.12-98.52% at pH in the range of 2-4 and that of bisphenol A was 92.18-95.62% at pH in the range of 2-10. The adsorption of bisphenol A and ibuprofen followed a pseudo-second-order kinetic and Langmuir model, and was a spontaneous endothermic process with the maximum adsorption amounts of 173.31 and 303.03 mg∙g^-1, respectively. The material presented favorable stability and reusability, and the removal efficiency of bisphenol A and ibuprofen after 5 cycles was still over 92.15% and 89.29%, respectively. Therefore, the prepared composite Fe₃O₄@COF-300 exhibited good performance in the adsorption of bisphenol A and ibuprofen in water.

Irreversible fluorine covalent organic framework based probe nanoelectrospray ionization mass spectrometry for direct and rapid determination of perfluoroalkyl carboxylic acids

Probe nanoelectrospray ionization mass spectrometry (PESI-MS) is practically desirable for rapid and ultra-sensitive analysis of trace contaminants in environment, but limited with the stable and selective probe coating. Herein, we show the design and preparation of irreversible fluorine-based covalent organic framework (TFPPA-F₄) covalently bonded probe to couple with ESI-MS (TFPPA-F₄-PESI-MS) for direct and rapid determination of perfluoroalkyl carboxylic acids (PFCAs) in environmental water. Chemical bonding coating of irreversible crystalline TFPPA-F₄ not only improved stability of the probe, but also offered accessible multiple interactions including hydrophobic, hydrogen bonding and F-F interactions to promote the kinetics and selectivity for PFCAs. The proposed TFPPA-F₄-PESI-MS realized rapid determination of PFCAs (about 4 min) with low limits of detection of 0.06-0.88 ng L^-1 and wide linear range of 1-5000 ng L^-1 (R² of 0.9982-0.9998). Recoveries for the spiked lake and pond water were 85.9-111.1 %. TFPPA-F₄ based probe can maintain the extraction performance after 100 times of extraction. This work shows the great potential of the irreversible covalent organic framework based PESI-MS in rapid and ultra-sensitive determination of contaminants in environmental samples.

Stable magnetic CoZn/N-doped polyhedron with self-generating carbon nanotubes for highly efficient removal of bisphenols from complex wastewaters

Bisphenols have extensively been found in various environmental matrices and caused public concerns due to their endocrine-disrupting potential. Herein, we developed a ZIF-67@ZIF-8-derived CoZn/nitrogen-doped carbon (CoZn/NC) as a robust adsorbent for bisphenols in wastewaters. The self-generating carbon nanotubes and the open metal sites provided sufficient adsorption sites. The Co component endowed the derivative with strong magnetism facilitating its separation from water. CoZn/NC exhibited exceeding water stability in pH 3 - 12 solution and withstood water up to 15 days. The great applicability of CoZn/NC was validated with 16 real wastewaters from different sources (recoveries exceeding 97.9%). Fast adsorption kinetics were observed with removal efficiencies above 96.5% within 1 min. The adsorption isotherms were well fitted with the Langmuir model, with adsorption capacities of 222, 200, 193, and 321 mg g^-1 for bisphenol A, bisphenol F, bisphenol S, and bisphenol AF, respectively. Variations in external conditions, including pH 3 - 9, humic acid (50 mg L^-1), and NaCl (0.1 mol L^-1), had negligible impacts on the adsorption process. The characterizations and density functional theory computation demonstrated that electrostatic, hydrophobic, π - π, and cation- π interactions are the driving forces in this system. The as-prepared CoZn/NC exhibits great promise in real wastewater treatment.

Recent applications of organic molecule-based framework porous materials in solid-phase microextraction for pharmaceutical analysis

Sample preparation is an indispensable part of detection of complex samples in pharmaceutical analysis. Solid-phase microextraction (SPME) has obtained a lot of attention due to its advantages of time saving, less solvent and easily automation. A variety of functional materials are used as sorbents in SPME to carry out selective and high extraction. This review centers around the recent applications of organic molecule-based framework porous materials, such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), as SPME coating materials mainly focus on pharmaceutical analysis in food, environment, and biological samples. Four representative extraction devices are introduced, including on-fiber SPME, in-tube SPME, thin film SPME, stir bar SPME. The application prospect of other organic porous materials as sorbents for pharmaceutical analysis are also discussed, such as hyper crosslinked polymers (HCPs) and conjugated microporous polymers (CMPs). The progresses and discusses are provided to offer references for further research focusing on application and development of organic molecule-based framework porous materials in the field of SPME.

An efficient 3D adsorbent foam based on graphene oxide/AgO nanoparticles for rapid vortex-assisted floating solid phase extraction of bisphenol A in canned food products

In this study, a three-dimensional adsorbent was developed based on graphene oxide/AgO nanoparticles over interconnected nickel foam (GO/AgO@Ni foam) for rapid and efficient vortex assisted floating solid phase extraction of bisphenol A in canned food products prior to high performance liquid chromatography with a fluorescence detector. The analytical techniques scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FT-IR) were used for characterization of the synthetized GO/AgO@Ni foam. The effect of proficiency factors including pH, foam size, vortexing time, salt addition, sample volume, desorption type and volume, and desorption time on the extraction efficiency of bisphenol A were explored through the matrix match method. Under the above experimental conditions, the figures of merit of the method were acquired as LODs (S/N = 3) of 0.18-0.84 μg kg^-1, LOQs of 0.61-2.81 μg kg^-1 (S/N = 10), linear ranges of 0.5-500 μg kg^-1, and enrichment factors of 235.5-244.9. The inter-day precision values (RSD%, n = 7) of 2.5-3.6 and the intra-day precision (%) of (5 days and seven replicates for each day) 2.8-3.8 were achieved for bisphenol A at a concentration of 50 μg kg^-1. The relative recoveries of 94.0% to 99.6% were obtained for the canned food samples.

Recent Advances in the Application of Covalent Organic Frameworks in Extraction: A Review

Covalent organic frameworks (COFs) are a class of emerging materials that are synthesized based on the covalent bonds between different building blocks. COFs possess unique attributes in terms of high porosity, tunable structure, ordered channels, easy modification, large surface area, and great physical and chemical stability. Due to these features, COFs have been extensively applied as adsorbents in various extraction modes. Enhanced extraction performance could be reached with modified COFs, where COFs are presented as composites with other materials including nanomaterials, carbon and its derivatives, silica, metal-organic frameworks, molecularly imprinted polymers, etc. This review article describes the recent advances, developments, and applications of COF-based materials being utilized as adsorbents in the extraction methods. The COFs, their properties, their synthesis approaches as well as their composite structures are reviewed. Most importantly, suggested mechanisms for the extraction of analyte(s) by COF-based materials are also discussed. Finally, the current challenges and future prospects of COF-based materials in extraction methods are summarized and considered in order to provide more insights into this field.

CO2 capture and a route to transform it in formic acid: a theoretical approach

New organic frameworks (COFs) employing two coronene molecules forced to adopt a parallel conformation thus forming a molecular reactor are proposed. These COFs exhibit different distances between the coronene units, thus creating diverse electronic environments. The simulation of the trapping of CO₂ and H₂ molecules in the reactor hollow having distinct anchor fragments yields in the two cases formic acid. The analysis of the reaction profile allowed us to propose a thermodynamically favored process. The nature of the frontier molecular orbitals in the involved processes is also discussed. Reaction profile of CO₂ and H₂ process to yield formic acid.

Silica Aerogel Hybridized with Melamine-Terephthalaldehyde Polymer for In-Tube Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons from Environment Water

To improve the extraction performance of the silica aerogel, a melamine-terephthalaldehyde polymer was used to hybridize silica aerogel, and the hybridized aerogel was coated on the surface of stainless steel wire to prepare a fiber-filled extraction tube through placing four wires into a polyetheretherketone tube. The tube was combined with high-performance liquid chromatography, then the online extraction and detection were established. Several polycyclic aromatic hydrocarbons (PAHs) were selected as the target analytes. Under the optimum extraction and desorption conditions, the limit of detection was as low as 3.0 ng L-1, and the linear range was 0.01-20.0 μg L-1. The enrichment factors of PAHs were in the range of 1724-2393. Three environmental water samples of mineral water, tap water and river water were analyzed by this method, and the recoveries that spiked at 1.0-10.0 μg L-1 were between 80.5-126%. It showed many advantages compared with other methods, such as better sensitivity, faster detection and online analysis.

Simultaneous preconcentration and pre-column derivatization for rapid analysis of nitrilotriacetic acid in environmental waters by high performance liquid chromatography

A simplified sample pretreatment procedure was developed for quantitative measurement of nitrilotriacetic acid (NTA) in environmental water. On the basis of coordination capacity between NTA and metal ions, aluminum-based metal organic framework (MOF, MIL-53(Al)) was adopted for the adsorption of NTA, followed by stripping with copper sulfate as the eluent. The adsorbed NTA was converted into Cu-NTA during the desorption process, which facilitated the ensuing measurement by high performance liquid chromatography (HPLC). A linear range within 0.10 - 10 mg L^-1 was achieved, along with a limit of detection (LOD, S/N=3, n=7) of 0.03 mg L^-1 and an enrichment factor of 10.4. The developed method was validated by the analysis of sea water, influent of wastewater treatment plant and industrial wastewater, with satisfactory recoveries (90.2 - 91.1%) obtained.

Design and preparation of functional azo linked polymers for the adsorptive removal of bisphenol A from water: Performance and analysis of the mechanism

In order to effectively remove refractory bisphenol A (BPA) from water, a novel nitrogen doped organic porous functional azo linked polymer (ALP-p) was designed and prepared according to the physicochemical characteristics of propane linked to two phenol hydroxyl groups. This ALP-p was synthesized with 98.5% yield, from pararosaniline and phloroglucinol, via the diazo coupling reaction to produce multiple adsorption functional groups of benzene ring, hydroxyl group and azo group. This functional material showed high adsorption capacity of 357.8 mg/g for 50 mg/L BPA, at 20 °C. The adsorption kinetics and isotherms were described by the pseudo-second-order and Langmuir model, respectively. The major adsorption mechanisms were attributed to the high specific surface area (259.8 m²/g) and pore volume (0.56 cm³/g) related surface adsorption and pore diffusion through porous stereoscopic stacking cavity anchorage. The functional group from the three-dimensional skeleton structures of ALP-p for BPA anchoring endowed chemisorption via π-π interaction between benzene rings and hydrogen-bonding (O-H⋯O, C-H⋯N, C-H⋯O and C-H⋯C) with the hydrogen atom of benzene ring, -OH from BPA and -OH, NN from ALP-p, respectively. The coexisting organic pollutants and alkali environment posed a negative effect on adsorption, while salinity had no significant effect on the process. The adsorption capacity and recovery of ALP-p were >93.5% and 81.6% after five cycles of operation.

Covalent organic framework-based porous materials for harmful gas purification

Covalent organic frameworks (COFs) with 2D or 3D networks are a class of novel porous crystalline materials, and have attracted more and more attention in the field of gas purification owing to their attractive physicochemical properties, such as high surface area, adjustable functionality and structure, low density, and high stability. However, few systematic reviews about the application statuses of COFs in gas purification are available, especially about non-CO₂ harmful gases. In this review, the recent progress of COFs about the capture, catalysis, and detection of common harmful gases (such as CO₂, NO_x, SO₂, H₂S, NH₃ and volatile pollutants) were comprehensively discussed. The design strategies of COF functional materials from porosity adjustment to surface functionalization (including bottom-up approach, post-synthetic approach, and blending with other materials) for certain application were summarized in detail. Furthermore, the faced challenges and future research directions of COFs in the harmful gas treatment were clearly proposed to inspire the development of COFs.

Efficient extraction of trace organochlorine pesticides from environmental samples by a polyacrylonitrile electrospun nanofiber membrane modified with covalent organic framework

Detecting and analyzing of the trace organochlorine pesticides (OCPs) in the real water has become a big challenge. In this work, a novel functional electrospun nanofiber membrane (PAN@COFs) was synthesized through the in situ growth of covalent organic frameworks (COFs) on a polyacrylonitrile electrospun nanofiber membranes under room temperature and used in the solid-phase micro-extraction (SPME) to enrich trace organochlorine pesticides (OCPs) in water. The resulted PAN@COFs composite consisted of numerous nanofibers coated ample porous COFs spheres (~ 500 nm) and owned stable crystal structure, abundant functional groups, good stability. In addition, the enrichment experiments clearly revealed that PAN@COFs exhibited rather outstanding performance on adsorbing the trace OCPs (as low as 10 ng L^-1) with the enrichment of 482-2686 times. Besides, PAN@COFs displayed good reusability and could be reused 100 times. Notably, in the real water samples (sea water and river water), the high enrichment factors and recovery rates strongly confirmed the feasibility of PAN@COFs for detecting the trace OCPs. Furthermore, due to the synergy of π-π stacking interaction and hydrophobic interaction between the OCPs molecules and PAN@COFs, the OCPs could be efficiently adsorbed on PAN@COFs, even under the extremely low driving force.

Efficient Extraction and Determination of Carbamate Pesticides in Vegetables Based on a Covalent Organic Frameworks with Acylamide Sites

It is an important challenge to effectively extract and determine pesticides in complex samples. Covalent organic frameworks (COFs) are burgeoning porous crystalline organic materials with good environmental resistance, thus demonstrating great potential as adsorbents in contaminants detection. In this work, we design and synthesize a novel COF-TpDB via 1,3,5-triformylphloroglucinol (Tp) and 4,4'-diaminobenzoylanilide (DB) as well as its packed cartridge for solid phase extraction (SPE) of carbamate pesticides. Simulation calculations showed H-bonding facilitates the adsorption interactions between the carbamate pesticides and TpDB. A method was developed by coupling TpDB as SPE sorbents with high performance liquid chromatography-ultraviolet (HPLC-UV) detection to determine trace carbamate pesticides in vegetables. The established method showed a wide linear range of 0.1-200 ng mL^-1 and low limit of detections (0.005-0.05 ng mL^-1) for four carbamate pesticides. The applicability of TpDB as adsorbent was investigated for determination of trace carbamate pesticides residue in vegetables with satisfactory recoveries of four carbamates in the range of 80.4-101.2%. The results demonstrated that the COF-TpDB offer great potential for efficient extraction of carbamate pesticides from complicate matrices.

Fabrication of stable multivariate metal-organic frameworks with excellent adsorption performance toward bisphenols from environmental samples

As a type of environmental endocrine disrupting chemicals, bisphenols (BPs) have a certain embryonic toxicity and teratogenicity, which can significantly increase the risks of breast cancer, prostate cancer, leukemia and other cancers. In this work, stable multivariate metal-organic frameworks (UiO-66-NH₂/TCPP_x) were synthesized via in situ one-pot method and used as miniaturized dispersive solid-phase extraction (dμSPE) sorbents for extraction of trace BPs from environmental samples. The phase purity, crystal morphology and physical properties of UiO-66-NH₂/TCPP_x samples were varied by adjusting the mass ratio of TCPP. The extraction performance of UiO-66-NH₂/TCPP_x samples were investigated and UiO-66-NH₂/TCPP_1.0 exhibited the highest adsorption efficiency. Besides, UiO-66-NH₂/TCPP_1.0 possessed excellent recycling stability for the adsorption and desorption of BPs more than 20 cycles. The experimental parameters including amount of adsorbent, adsorption time, sample solution pH, temperature, desorption time and desorption solvents which affecting the efficiency of dμSPE were studied, respectively. Good linearity (R² > 0.9992) in range of 0.1-200 ng mL^-1 was obtained. The detection limits (S/N = 3) and quantification limits (S/N = 10) were achieved at 0.03-0.08 ng mL^-1 and 0.1-0.5 ng mL^-1, respectively. The relative standard deviations (RSDs) of intra-day and inter-day ranged from 2.5 to 5.5% and 1.1-6.8%. Enrichment factors were calculated in the range of 303-338. The obtained recoveries of bisphenol F (BPF), bisphenol A (BPA), bisphenol B (BPB) and bisphenol AF (BPAF) were 81.26-91.03% (RSDs = 0.96-6.47%), 82.2-97.27% (RSDs = 0.45-6.15%), 87.56-97.26% (RSDs = 1.1-6.22%) and 82.2-100.8% (RSDs = 0.46-4.07%). The UiO-66-NH₂/TCPP_1.0 can be employed as potential dμSPE sorbents for the enrichment of trace BPs in the environmental samples.

Applications of covalent organic frameworks and their composites in the extraction of pesticides from different samples

Pesticides are used extensively in a wide range of applications and due to their high rate of consumption, they are ubiquitous in the different media and samples like environment, water sources, air, soil, biological materials, wastes (liquids, solids or sludges), vegetables and fruits, where they can persist for long periods. Pesticides often have hazardous side effects and can cause a range of harmful diseases like Parkinson, Alzheimer, asthma, depression and anxiety, cancer, etc, even at low concentrations. To this end, extraction, pre-concentration and determination of pesticides from various samples presents significant challenges caused by sample complexity and the low concentrations of them in many samples. Often, direct extraction and determination of pesticides are impossible due to their low concentrations and the complexity of samples. The main goals of sample preparation are removing interfering species, pre-concentrating target analyte/s and converting the analytes into more stable forms (when needed). The most popular approach is solid-phase extraction due to its simplicity, efficiency, ease of operation and low cost. This method is based on using a wide variety of materials, among which covalent organic frameworks (COFs) can be identified as an emerging class of highly versatile materials exhibiting advantageous properties, such as a porous and crystalline structure, pre-designable structure, high physical and chemical stability, ease of modification, high surface area and high adsorption capacity. The present review will cover recent developments in synthesis and applications of COFs and their composites for extraction of pesticides, different synthesis approaches of COFs, possible mechanisms for interaction of COFs-based adsorbents with pesticides and finally, future prospects and challenges in the fabrication and utilization of COFs and their composites for extraction of pesticides.

[Recent advance of new sample preparation materials in the analysis and detection of environmental pollutants]

To successfully analyze complex samples and detect trace targets, sample pretreatment is essential. Efficient sample pretreatment techniques can remove or reduce interference from the sample matrix. It can also enrich analytes, thereby improving analytical accuracy and sensitivity. In recent years, various sample preparation techniques, including SPE, magnetic dispersion SPE, pipette tip SPE, stir bar extraction, fiber SPME, and in-tube SPME, have received increasing attention in environmental analysis and monitoring. The extraction efficiency mainly depends on the type of adsorbent material. Therefore, the development of efficient adsorbents is a crucial step toward sample preparation. This review summarizes and discusses the research advances in extraction materials over recent years. These extraction materials contain inorganic adsorbents, organic adsorbents, and inorganic-organic hybrid materials such as graphene, graphene oxide, carbon nanotubes, inorganic aerogels, organic aerogels, triazinyl-functionalized materials, triazine-based polymers, molecularly imprinted polymers, covalent organic frameworks, metal-organic frameworks, and their derivatives. These materials have been applied to extract different types of pollutants, including metal ions, polycyclic aromatic hydrocarbons, plasticizers, alkanes, phenols, chlorophenols, chlorobenzenes, polybrominated diphenyl ethers, perfluorosulfonic acids, perfluorocarboxylic acids, estrogens, drug residues, and pesticide residues, from environmental samples (such as water and soil samples). These sample preparation materials possess high surface areas, numerous adsorption sites, and allow extraction via various mechanisms, such as π-π, electrostatic, hydrophobic, and hydrophilic interactions, as well as hydrogen and halogen bond formation. Various sample pretreatment techniques based on these extraction materials have been combined with various detection methods, including chromatography, mass spectrometry, atomic absorption spectroscopy, fluorescence spectroscopy, and ion mobility spectroscopy, and have been extensively used for the determination of environmental pollutants. The existing challenges associated with the development of sample preparation techniques are proposed, and prospects for such extraction materials in environmental analysis and monitoring are discussed. Major trends in the field, including the development of efficient extraction materials with high enrichment ability, good selectivity, excellent thermal stability, and chemical stability, are discussed. Green sample pretreatment materials, environmentally friendly synthesis methods, and green sample pretreatment methods are also explored. Rapid sample pretreatment methods that can be conducted within minutes or seconds are of significant interest. Further, online sample pretreatment and automatic analysis methods have attracted increasing attention. Besides, real-time analysis and in situ detection have been important development directions, and are expected to be widely applicable in environmental analysis, biological detection, and other fields. Modern synthesis technology should be introduced to synthesize specific extraction materials. Controllable preparation methods for extraction materials, such as the in situ growth or in situ preparation of extraction coatings, will acquire importance in coming years. It will also be important to adopt high-performance materials from other fields for sample pretreatment. Organic-inorganic hybrid extraction materials can combine the advantages both organic materials and inorganic materials, and mutually compensate for any disadvantages. Extraction materials doped with nanomaterials are also promising. Although existing sample pretreatment techniques are relatively efficient, it is still imperative to develop novel sample preparation methods.

[Advances in solid-phase extraction for bisphenols in environmental samples]

Owing to the strict restrictions on the production and use of bisphenol A (BPA), bisphenol analogs (e. g., bisphenol S and bisphenol F) are gradually coming to use in many fields. BPA and these bisphenol analogs are so-called bisphenols (BPs). BPs as a class of endocrine disrupters are widely distributed in the environment (water, sediments, sludge, and aquatic products). BPs enter the human body through various routes, leading to endocrine disruption, cytotoxicity, genotoxicity, reproductive toxicity, dioxin-like effects, and neurotoxicity. The Canadian government has identified BPs as substances for further scoping/problem formulation. Because of the widespread attention paid to BPs in the environmental field, research is being expanded to cover water, sediment, dust, and biological samples, and other media. Given the significant differences in the complexity and pollution concentration of environmental samples, the development of pretreatment methods that afford high extraction efficiency, good purification selectivity, strong universality, operational simplicity, and high-throughput extraction and purification, are necessary to realize the highly sensitive detection of BPs in environmental media. In recent years, solid-phase extraction (SPE), accelerated solvent extraction (ASE), microwave-assisted extraction (MAE), and dispersion liquid-liquid-microextraction (DLLME) as new pretreatment technologies have gradually replaced the traditional liquid-liquid extraction and Soxhlet extraction. SPE has seen rapid development for the extraction and purification of BPs in various environmental samples, overcoming the bottlenecks related to time, energy, and solvent consumption in traditional methods while extending technical support for the analysis of emerging pollutants. The physicochemical properties, usage, and environmental hazards of typical BPs were briefly reviewed, with emphasis on the application of SPE products, development of new adsorbents, and transformation of the SPE mode. Commercialized SPE products are universally applicable in the field of environmental monitoring, while products suitable for the pretreatment of BPs are limited. The development of new adsorbents mainly focused on their adsorption capacity and selectivity. For example, ordered mesoporous silicon, carbon nanomaterials, metal-organic frameworks, and cyclodextrins have large surface areas, good adsorption performance, and regular pore structures, which improve the adsorption capacity of BPs. Molecularly imprinted polymers (MIPs) and mixed-mode ion-exchange polymers are mainly used to improve the selectivity of BPs in the purification process. In addition, MIPs have high chemical, mechanical, and thermal stabilities, which ensures their widespread application in the extraction, preconcentration, and separation of BPs. A variety of new SPE adsorbents can partially meet the diverse needs for detection. There is a consensus that the current challenges in analytical chemistry include the determination of contaminants at low concentration levels, but at the same time, more efficient and environment-friendly methodologies are required. With the introduction of high-sensitivity instruments in the market, the SPE model is seeing gradual development in terms of miniaturization, automation, and simplification. This in turn has minimized solvent consumption, analysis time, and labor cost, resulting in more efficient and affordable analytical methods such as QuEChERS, solid-phase microextraction (SPME), and magnetic solid-phase extraction (MSPE) to adapt to the new development scenario.

Sample bottle coated with sorbent as a novel solid-phase extraction device for rapid on-site detection of BTEX in water

Solid-phase extraction (SPE) is a popular technique for environmental sample pretreatment. However, SPE usually requires complex sample pretreatment processes, which is time-consuming and inconvenient for real-time and on-site monitoring. Herein, a solvent-free, rapid, and user-friendly SPE device was developed by coating the polydimethylsiloxane (PDMS)/divinylbenzene (DVB) sorbent on the inner wall of a sample bottle. The extraction process and desorption process were both carried out in the bottle. The analytes trapped in the sorbent were thermally desorbed and simultaneously sucked out from the bottle by an air sampling tube equipped on field-portable GC-MS. Different to previous work, the sample pretreatment process didn't require any complicated and time-consuming steps, such as centrifugation or filtration. The total analysis time for each sample was less than 25 min, which was feasible for rapid on-site detection, and thus avoided the losses and contamination of samples in conventional sample storage and transportation processes. Under optimal conditions, the proposed SPE method exhibited wide linear ranges, low detection limits (0.010-0.036 μg L^-1, which were much lower than the maximum levels restricted by the US Environmental Protection Agency and the Chinese GB3838-2002 standard), good intra-bottle repeatability (6.13-7.17%, n = 3) and satisfactory inter-bottle reproducibility (4.73-6.47%, n = 3). Finally, the method was successfully applied to the rapid detection of BTEX in the field. The recoveries of BTEX in spiked water samples ranged from 89.1% to 116.2%. This work presents a novel SPE approach for rapid on-site monitoring in water samples.

In-situ synthesis of nanocubic cobalt oxide @ graphene oxide nanocomposite reinforced hollow fiber-solid phase microextraction for enrichment of non-steroidal anti-inflammatory drugs from human urine prior to their quantification via high-performance liquid chromatography-ultraviolet detection

The in-situ synthesis and application of nanocubic Co₃O₄-coated graphene oxide (Co₃O₄@ GO) was introduced for the first time to present a cost-effective, stable and convenient operation and a simple device for hollow fiber solid-phase microextraction (HF-SPME) of four selected nonsteroidal anti-inflammatory drugs (NSAIDs) including diclofenac, mefenamic acid, ibuprofen and indomethacin. The extracted analytes were desorbed by an appropriate organic solvent and analyzed via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared sorbent was approved using different characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The variables effective on the Co₃O₄@GO-HF-SPME method including extraction time, desorption time, desorption solvent volume, sample pH, stirring rate and ionic strength were screened via Plackett-Burman design and then optimized by Box-Behnken design. Under optimal condition, the calibration curves were linear within the range of 1.0-200.0 µg L^-1 of analyte concentration with detection limits of 0.18-1.1 µg L^-1 and the relative standard deviations less than 10.1%. The limits of quantification (LOQs) were in the range of 0.60-3.67 µg L^-1. Matrix effect was not observed with this method; therefore, standard addition is not necessary for quantification of target compounds. The enrichment factors were obtained in the range of 49-68. The relative recoveries of the urine sample analysis were calculated in the range of 93-102%. Finally, the presented method exhibited good sensitivity, excellent repeatability, high reusability and acceptable precision, which will be a promising method to analyze various nonsteroidal anti-inflammatory drugs in urine samples.