An amine-functionalized olefin-linked covalent organic framework used for the solid-phase microextraction of legacy and emerging per- and polyfluoroalkyl substances in fish

Multiple-component covalent organic frameworks for simultaneous extraction and determination of multitarget pollutants in sea foods

Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have been raising global concerns due to their toxic effects on environment and human health. The monitoring of residues of POPs in seafood is crucial for assessing the accumulation of these contaminants in the study area and mitigating potential risks to human health. However, the diversity and complexity of POPs in seafood present significant challenges for their simultaneous detection. Here, a novel multi-component fluoro-functionalized covalent organic framework (OH-F-COF) was designed as SPE adsorbent for simultaneous extraction POPs. On this basis, the recognition and adsorption mechanisms were investigated by molecular simulation. Due to multiple interactions and large specific surface area, OH-F-COF displayed satisfactory coextraction performance for PFASs, PCBs, and BPs. Under optimized conditions, the OH-F-COF sorbent was employed in a strategy of simultaneous extraction and stepwise elution (SESE), in combination with HPLC-MS/MS and GC-MS method, to effectively determined POPs in seafood collected from coastal areas of China. The method obtained low detection limits for BPs (0.0037 -0.0089 ng/g), PFASs (0.0038 -0.0207 ng/g), and PCBs (0.2308 -0.2499 ng/g), respectively. This approach provided new research ideas for analyzing and controlling multitarget POPs in seafood. ENVIRONMENTAL IMPLICATIONS: Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have caused serious hazards to human health and ecosystems. Hence, there is a need to develop a quantitative method that can rapidly detect POPs in environmental and food samples. Herein, a novel multi-component fluorine-functionalized covalent organic skeletons (OH-F-COF) were prepared at room temperature, and served as adsorbent for POPs. The SESE-SPE strategy combined with chromatographic techniques was used to achieve a rapid detection of POPs in sea foods from the coastal provinces of China. This method provides a valuable tool for analyzing POPs in environmental and food samples.

Hydrazone-linked covalent organic framework functionalized with cysteine as a fluorescence sensor and Exploration of paper chip for p-nitrophenol detection

The large use and emission of p-nitrophenol (p-NP) seriously pollute the environment and endanger human health. In this work, a hydrazone-linked fluorescent covalent organic framework (BATHz-COF) was simply synthesized at room temperature and covalently linked N-acetyl-L-cysteine (NALC) via the "thiol-ene" click reaction, where carboxyl groups were introduced to improve dispersion and fluorescence intensity. As a rapid, good selectivity and reusability fluorescence sensor, the obtained COF-NALC has been used for quantitative analysis of p-NP predicated on the internal filtering effect (IFE). Under optimal conditions, COF-NALC enabled quantitative detection of p-NP with a linear range of 5-50 μM and the detection limit was 1.46 μM. The application of COF-NALC to the detection of p-NP in river water samples was successful, and the satisfactory recoveries were 98.0%-109.3%. Furthermore, the fluorescent COF paper chips constructed by in situ growth were combined with a smartphone to build a visual platform for the quick and real-time detection of p-NP, providing an excellent illustration for the development of intelligent fluorescence sensing in environmental analysis.

Oxolinic Acid Generated Green Fluorescence Based on a Terbium-Functionalized Covalent Organic Framework

Oxolinic acid (OXO), a classic environmental contaminant, has a terrible detrimental effect on human health. The exploration of efficient strategies to detect and detecting OXO has remarkable significance. Herein, we reported a novel terbium(III)-functionalized covalent organic framework (Bpy-DhBt-COF@Tb3+) by fixing Tb3+ on the bipyridine-connecting COF (Bpy-DhBt-COF) as a turn-on fluorescent switch toward OXO for the first time. In this platform, Tb3+ acts as the specific recognition units for OXO and the response signal, while Bpy-DhBt-COF acts as the safehaven for Tb3+. Once introducing OXO to Bpy-DhBt-COF@Tb3+, OXO can instead water molecules coordinate with Tb3+ and sensitize Tb3+ instantly, thereby producing a significant fluorescence signal. Profiting from the excellent porosity of Bpy-DhBt-COF@Tb3+, it can obtain optimal response toward OXO only within 10 s with an ultrasensitive detection limit of 12.5 nM. Furthermore, Bpy-DhBt-COF@Tb3+ displayed outstanding selectivity toward OXO than other general quinolones. Based on these, a Tb3+-based COF was explored for the first time for the turn-on fluorescence detection of an OXO with rapid response, high sensitivity, and outstanding selectivity. In this work, we not only exhibit the attractive performance of Tb3+-functionalized COF to detect OXO but also propose a prospect strategy for creating other fluorescent sensors for multiple targets.

One step cleanup of 160 pesticides and veterinary drugs in aquatic products using melamine-based automatic pressure filtration purification method combined with HPLC-MS/MS

A 15-channel pressure filtration purification method was presented for high throughput sample preparation of aquatic products. A cost-effective device was constructed and melamine sponge was selected as the cleanup sorbent. Upon interfacing with HPLC-MS/MS, the analytical procedure demonstrated its suitability for quantifying 160 pesticides and veterinary drug residues in aquatic products such as fish, shrimp, and crab. The method achieved sample recoveries ranging from 61.3 to 124.9 %. The detection limits were established between 0.5 and 1.0 μg/kg, while the quantitation limits were confirmed to be within the range of 1.0-2.0 μg/kg. The method was applied to quantify the pesticide and veterinary drug residues in mostly consumed aquatic products from five coastal provinces in China. The results showed significant differences between different aquatic products in the concentrations of pesticide and veterinary drug residues, implying the necessity of supervision for the accurate determination of pesticides and veterinary drugs.

Efficient removal of per/polyfluoroalkyl substances from water using recyclable chitosan-coated covalent organic frameworks: Experimental and theoretical methods

Covalent organic frameworks (COFs) demonstrate remarkable potential for adsorbing per/polyfluoroalkyl substances (PFAS). Nevertheless, the challenge of recycling powdered COFs hampers their practical application in water treatment. In this research, a quaternary amine COF with inherent positive surface charge was synthesised to adsorb perfluorooctanoic acid (PFOA) via electrostatic interactions. The COF was then combined with chitosan (CS) through a simple dissolution-evaporation process, resulting in a composite gel material termed COF@CS. The findings indicated that the adsorption capacity of COF@CS significantly surpassed that of the original COF and CS. According to the Langmuir model, COF@CS achieved a maximum PFOA capacity of 2.8 mmol g-1 at pH 5. Furthermore, the adsorption rate increased significantly to 6.2 mmol g-1 h-1, compared to 5.9 mmol g-1 h-1 for COF and 3.4 mmol g-1 h-1 for CS. Notably, COF@CS exhibited excellent removal efficacy for ten other types of PFAS. Moreover, COF@CS could be successfully regenerated using a mixture of 70% ethanol and 1 wt% NaCl, and it exhibited stable reusability for up to five cycles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) characterisation, and theoretical calculations revealed that the quaternary amine functional group in COF served as the primary adsorption site in the composite gel material, while the protonated amino group on CS enhanced PFOA adsorption through electrostatic interaction. This study highlights the significant practical potential of COF@CS in the removal of PFAS from aqueous solution and environmental remediation.

Fluorine-functionalized magnetic amino microporous organic network for enrichment of perfluoroalkyl substances

Perfluoroalkyl substances (PFAS) are persistent organic pollutants that pose significant risks to human health and the environment. Efficient and selective enrichment of these compounds was crucial for their accurate detection and quantification in complex matrices. Herein, we report a novel magnetic solid-phase extraction (MSPE) method using fluorine-functionalized magnetic amino-microporous organic network (Fe3O4@MONNH2@F7) adsorbent for the efficient enrichment of PFAS from aqueous samples. The core-shell Fe3O4@MONNH2@F7 nanosphere was synthesized, featuring magnetic Fe3O4 nanoparticles as the core and a porous amino-functionalized MONs coating as the shell, which was further modified by fluorination. The synthesized adsorbent material exhibited high specific surface area, hydrophobicity, and abundant fluorine groups, facilitating efficient and selective adsorption of PFAS via electrostatic attraction, hydrophobic-hydrophobic interactions, fluorine-fluorine interactions, π-CF interactions and hydrogen bonding. Furthermore, the MSPE method coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) allowed for the rapid, sensitive, and accurate determination of ultra-trace PFAS in real water samples, human serum, and human follicular fluid. Under optimal conditions, the established MSPE method demonstrated a linear range (2 to 2000 ng L-1), with a correlation coefficient exceeding 0.9977, low limits of detection ranging from 0.54 to 1.47 ng L-1, with a relative standard deviation (RSD) < 9.1%. Additionally, the method showed excellent performance in complex real samples (recovery ratio of 81.7 to 121.6 %). The adsorption mechanism was investigated through kinetic, isotherm, and molecular simulation studies, revealing that the introduction of fluorine groups enhanced the hydrophobic interaction and fluorine-fluorine attraction between the adsorbent and PFAS. This work provides a proof-of-concept strategy for designing adsorbent materials with high efficiency and selectivity by post-modification, which has great potential for the detection and analysis of PFAS in complex samples.

Deciphering the relationship between the ordered pore structure and solid-phase microextraction behavior of covalent organic frameworks for phenols

The extraction performance of materials is highly related to their physical structure. However, the precise impact of ordered pore structure in covalent organic frameworks (COFs) on extraction performance are still puzzling. To look insight into this, a series of COFs with varying degrees of ordered pore structures were prepared at room temperature by adjusting reaction time and their extraction efficiencies toward phenolic compounds were investigated. The experimental results revealed that the COF with a short range ordered pore structure exhibited a higher affinity for phenolic compounds along with a larger enrichment factor, while the COF with a long range ordered pore structure demonstrated faster extraction kinetics. The investigation into interaction mechanism revealed that the density of available sites is responsible for these differences. Taking COF-OMe-0.5 h as solid-phase microextraction fiber coating, a highly efficient and sensitive quantitative analysis method for phenolic compounds was established by combining it with gas chromatograph-mass spectrometer. The established method boasts high enrichment factors (7192-29440), wide linear ranges (2.0-10000 ng L-1), and low detection limits (0.24-0.54 ng L-1). This study provides a conceptual guide for constructing desirable COFs with controlled pore structures for specific applications.

All-in-one strategy to construct bifunctional covalent triazine-based frameworks for simultaneous extraction of per- and polyfluoroalkyl substances and polychlorinated naphthalenes in foods

Per- and polyfluoroalkyl substances (PFASs) and polychlorinated naphthalenes (PCNs) are of growing concern due to their toxic effects on the environment and human health. There is an urgent need for strategies to monitor and analyze the coexistence of PFASs and PCNs, especially in food samples at trace levels, to ensure food safety. Herein, a novel β-cyclodextrin (β-CD) derived fluoro-functionalized covalent triazine-based frameworks named CD-F-CTF was firstly synthesized. This innovative framework effectively combines the porous nature of the covalent organic framework and the host-guest recognition property of β-CD enabling the simultaneous extraction of PFASs and PCNs. Under the optimal conditions, a simple and rapid method was developed to analyze PFASs and PCNs by solid-phase extraction (SPE) based simultaneous extraction and stepwise elution (SESE) strategy for the first time. When coupled with liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS), this method achieved impressive detection limits for PFASs (0.020 -0.023 ng/g) and PCNs (0.016 -0.075 ng/g). Furthermore, the excellent performance was validated in food samples with recoveries of 76.7-107 % (for PFASs) and 78.0-108 % (for PCNs). This work not only provides a simple and rapid technique for simultaneous monitoring of PFASs and PCNs in food and environmental samples, but also introduces a new idea for the designing novel adsorbents with multiple recognition sites.

Substitution and Orientation Effects on the Crystallinity and PFAS Adsorption of Olefin-Linked 2D COFs

Solid phase adsorbents with high removal affinity for per- and polyfluoroalkyl substances (PFAS) in aqueous environments are sought. We report the synthesis and investigation of COF-I, a new covalent organic framework (COF) with a good affinity for PFAS adsorption. COF-I was synthesized by the condensation reaction between 2,4,6-trimethyl-1,3,5-triazine and 2,3-dimethoxyterephthaldehyde and fully characterized. In addition to the high crystallinity and surface area, COF-I showed high hydrolytic and thermal stability. Further, we converted its hydrophobic surface to a hydrophilic surface by converting the ortho-methoxy groups to hydroxyl derivatives and produced a new hydrophilic olefin-linked two-dimensional (2D) COF. We experimentally measured the crystallinity of both COFs by X-ray diffraction and used atomistic simulations coupled with cross-polarization/magic angle spinning solid-state nuclear magnetic resonance (CP/MAS ssNMR) to determine the relative amounts of AA-stacking and AB-stacking present. COF-I, with its hydrophobic surface and methoxy groups in the ortho positions, showed the best PFAS adsorption. COF-I reduced the concentration of perfluorooctanoic acid from 20 to 0.069 μg L-1 and to 0.052 μg L-1 for perfluorooctanesulfonic acid. These amounts are lower than the U.S. Environmental Protection Agency advisory level (0.070 μg L-1). High efficiency, fast kinetic adsorption, and reusability of COF-I are advantages of COF-I for PFAS removal from water.

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.

Polymeric ionic liquid sorbent coatings in thin film microextraction: Insight into sorbent selectivity for pesticides and cannabinoids

Polymeric ionic liquid (PIL) sorbent coatings consisting of polymerizable cations and anions were employed as sorbent coatings in thin film microextraction (TFME) for the extraction of pesticides and cannabinoids. The blades consisted of a thin film of PIL sorbents chemically bonded to vinyltrimethoxysilane-functionalized nitinol sheets. The imidazolium- or ammonium-based PIL sorbents contained aromatic benzyl moieties as well as polar hydroxyl groups or aliphatic functional groups within the chemical structure of the IL monomer. The chemical structure of the IL crosslinkers of the PILs were kept constant across each sorbent, except for the anion, which consisted of either bis[(trifluoromethyl)sulfonyl]imide ([NTf2-]), p-styrenesulfonate ([SS-]), or 3-sulfopropyl acrylate ([SPA-]). Temperature, salt content, and methanol content were optimized as extraction conditions to maximize pesticide-cannabinoid selectivity using Doehlert design of experiments (DOE). Effects of these three factors on selectivity and extraction efficiency are discussed. The optimal extraction conditions consisting of sample temperature (31°C), sodium chloride (30% w/v), and methanol content (0.25% v/v) are compared to initial sorbent screening conditions at a sample temperature of 40°C, 15% (w/v) sodium chloride, and 2.5% (v/v) methanol content. PIL sorbent swelling behavior at different salt and methanol content conditions and its effect on extraction efficiency are hypothesized. Selectivity factors for the sorbents indicated that aromatic moieties within the IL monomer may enhance pesticide-cannabinoid selectivity under optimized conditions, but the extraction efficiency of pesticides that are known to coelute with cannabinoids in the chromatographic separation may be enhanced by employing sorbent coatings with [SPA-] anions.

Highly graphitized porous carbon/reduced graphene oxide for ultrahigh enrichment and ultrasensitive determination of polycyclic aromatic hydrocarbons

There is an urgent need to develop efficient and reliable coating materials for solid phase microextraction (SPME), in order to quantify and monitor pollutants in environmental waters. Herein, a highly graphitized porous carbon/reduced graphene oxide (PC/rGO) was successfully synthesized by pyrolysis of metal organic framework/graphene oxide precursors, and used as a SPME coating for ultrahigh enrichment of polycyclic aromatic hydrocarbons (PAHs) from water. The as-prepared PC/rGO exhibited high degree of graphitization, abundant number of micro/mesopores along with exceptional thermal stability, making it an ideal SPME coating material. The PC/rGO fiber offered an ultrahigh enrichment factor for PAHs (up to 126057), which could be attributed to the multiple interactions between the PC/rGO and PAHs, including hydrophobic and π-π interactions, partitioning, and mesopore filling effect. In the analysis of PAHs, the PC/rGO fiber showed a wide linearity (0.007-100 ng mL-1), low limits of detection (0.0005-0.005 ng mL-1), and good repeatability (RSDs <10.1%, n = 5) under optimized conditions. The established method was applicable for ultrasensitive determination of PAHs in different environmental waters and showed satisfactory recoveries. This study provides a novel way for constructing thermally stable SPME coating having efficient extraction performance.

Calix[4]arene-based covalent organic frameworks with host-guest recognition for selective adsorption of six per- and polyfluoroalkyl substances in food followed by UHPLC-MS/MS detection

Long-term ingestion or exposure to food contaminated with per- and polyfluoroalkyl substances (PFASs) may cause potential harm to human health. Due to the low contents of PFASs in complex food matrices, it is of great significance to develop adsorbents with excellent properties to enrich PFASs before analysis. Herein, calix[4]arene (CX4) was used as building block to prepare ordered crystalline covalent organic frameworks (COFs). The perfect combination of the host-guest recognition ability of CX4 and the porosity of COFs makes the CX4-COFs selective and high adsorption capacity for linear molecular PFASs (261-1055 mg/g). The adsorption behavior and mechanism were verified by isotherm adsorption experiments and simulation calculations. The CX4-COFs were then used as adsorbents for membrane solid-phase extraction (M-SPE), combined with ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) to determine PFASs in food. The method has low detection limits (0.11-0.28 ng/kg) and good precision (1.3%-9.8%), and has been successfully applied to the simultaneous enrichment and determination of six PFASs in fish, shrimp and shellfish. Satisfactory recoveries (79.9%-118%) were obtained. This study provides a new strategy for preparing CX4-COFs containing macrocyclic molecules with different morphologies and expands the application of COFs as attractive enrichment media for sample pretreatment.

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.

An ultrastable 2D covalent organic framework coating for headspace solid-phase microextraction of organochlorine pesticides in environmental water

Herein, a quinoline-linked ultrastable 2D covalent organic framework (COF-CN) coated fiber was successfully prepared and used for highly-sensitive headspace solid-phase microextraction (HS-SPME) of organochlorine pesticides (OCPs) in environmental water. The extraction efficiency of the COF-CN coating for all 14 OCPs was higher than that of four commercial SPME fiber coatings and most of the published works, with enrichment factors ranging from 540 to 5065. In combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), a wide linear range (0.05-200 ng/L), low detection limits (LODs, 0.0010-13.54 ng/L) and satisfactory reproducibility and repeatability were obtained under optimal conditions. Compared with the published works, the LODs of the developed technique were improved 2-5.9 times, and the enrichment factors (EFs) of the developed method were enhanced at least 2 times. The COF-CN coated fiber can be easily recycled and reused at least 70 times without any washing step. The adsorption mechanism was first characterized by density functional theory calculations and X-ray photoelectron spectroscopy analysis. Besides, the established method was successfully applied to the analysis of the distribution of trace OCPs in real water samples from Henan Province. All these results proved the promising application of the developed HS-SPME-GC-MS/MS method for organic pollutants analysis in water samples.

Online solid-phase extraction based on size-controllable spherical covalent organic framework for efficient determination of polybrominated diphenyl ethers in foods

An analytical method of microspheric brominated covalent organic framework (Br-COF)-online solid-phase extraction integrated with high-performance liquid chromatography (online SPE-HPLC) was proposed for efficiently enriching six polybrominated diphenyl ethers (PBDEs) in foods. The Br-COF microspheres were facilely prepared with uniformity and dispersion by a size-controllable synthesis at the room temperature. Attributed to multiple interactions of the halogen bonding, Van der Waals forces, hydrophobic interaction along with size-matching effect, Br-COF performed satisfactory extraction capacity for PBDEs compared with commercial adsorbents. Five primary influencing factors were optimized, including loading solvent, loading flow rate, elution solvent, elution flow rate and elution volume. Under the optimal parameters, the implement displayed excellent linear ranges (0.5-500 ng mL^-1) and low detection limits (0.01-0.05 ng mL^-1). The relative recoveries in six spiked food samples ranged from 87.8 to 119.7 % with relative standard deviations below 10 %. This research estabished a promising platform for quantitatively determining trace PBDEs in complex foods.

Efficient selective removal of uremic toxin precursor by olefin-linked covalent organic frameworks for nephropathy treatment

Indoxyl sulfate is a protein-bound uremic toxin synthesized from indole that cannot be efficiently removed by the hemodialysis method and thus becomes a key risk factor for the progression of chronic kidney disease. Here, we develop a non-dialysis treatment strategy to fabricate an ultramicroporous olefin-linked covalent organic framework with high crystallinity in a green and scalable fashion for selectively removing the indoxyl sulfate precursor (i.e., indole) from the intestine. Various analyses show that the resulting material exhibits excellent gastrointestinal fluid stability, high adsorption efficiency, and good biocompatibility. Notably, it realizes the efficient and selective removal of indole from the intestine and significantly attenuates serum indoxyl sulfate level in vivo. More importantly, the selective removal efficacy of indole is substantially higher than that of the commercial adsorbent AST-120 used in the clinic. The present study opens up a new avenue to eliminate indoxyl sulfate by a non-dialysis strategy and further expands the in vivo applications of covalent organic frameworks.

Facile Synthesis of Quinolinecarboxylic Acid-Linked Covalent Organic Framework via One-Pot Reaction for Highly Efficient Removal of Water-Soluble Pollutants

To efficiently eliminate highly polar organic pollutants from water has always been a difficult issue, especially in the case of ultralow concentrations. Herein, we present the facile synthesis of quinolinecarboxylic acid-linked COF (QCA-COF) via the Doebner multicomponent reaction, possessing multifunction, high specific surface area, robust physicochemical stability, and excellent crystallinity. The marked feature lies in the quinolinyl and carboxyl functions incorporated simultaneously to QCA-COF in one step. The major cis-orientation of carboxyl arms in QCA-COF was speculated by powder X-ray diffraction and total energy analysis. QCA-COF demonstrates excellent adsorption capacity for water-soluble organic pollutants such as rhodamine B (255.7 mg/g), methylene blue (306.1 mg/g), gentamycin (338.1 mg/g), and 2,4-dichlorophenoxyacetic acid (294.1 mg/g) in water. The kinetic adsorptions fit the pseudo-second order model and their adsorption isotherms are Langmuir model. Remarkably, QCA-COF can capture the above four water-soluble organic pollutants from real water samples at ppb level with higher than 95% removal efficiencies and excellent recycling performance.

Olefin-linked cationic covalent organic frameworks for efficient extraction of ReO4-/99TcO4. JOURNAL OF HAZARDOUS MATERIALS 2023;446:130603. [PMID: 36580784 DOI: 10.1016/j.jhazmat.2022.130603]

Efficient extraction of radioactive ⁹⁹TcO₄^- from strong acid/base solutions by porous adsorbents is extremely desirable but remains a great challenge. To overcome the challenge, here we report the first example of an olefin-linked cationic covalent organic framework (COF) named BDBI-TMT with excellent acid, base and radiation stability is synthesized by integrating robust imidazolium salt-based linkers with triazine building blocks. BDBI-TMT shows an ultra-fast adsorption kinetics (equilibrium is reached within 1 min) and an excellent ReO₄^- (a non-radioactive surrogate of ⁹⁹TcO₄^-) capture capacity of 726 mg g^-1, which can be attributed to the abundance of precisely tailored imidazolium salt-based units on the highly accessible pore walls of the ordered pore channels. Furthermore, the formation of the highly conjugated bulky alkyl skeleton enhances the hydrophobicity of BDBI-TMT, which significantly improves not only the affinity toward ReO₄^-/⁹⁹TcO₄^- but also the chemical stability, allowing selective and reversible extraction of ReO₄^-/⁹⁹TcO₄^- even under extreme conditions. This work demonstrates the great potential of olefin-linked cationic COFs for ReO₄^-/⁹⁹TcO₄^- extraction, providing a new avenue to construct high-performance porous adsorbents for radionuclide remediation.

Covalent triazine-based frameworks for efficient solid-phase microextraction of phthalic acid esters from food-contacted plastics

Owing to various health threats associated with phthalic acid esters (PAEs), this category of endocrine-disrupting compounds has attracted more and more public scrutiny. However, the efficient preconcentration of PAEs from complex food-contacted plastics still remains challenging. Herein, three covalent triazine-based frameworks (CTFs) were constructed by facile Friedel-Crafts reactions of cyanuric chloride (CC), with triptycene (TPC), fluorene (FL) and 1,3,5-triphenylbenzene (TPB), respectively. Three CTFs were then employed as solid-phase microextraction (SPME) coatings for the extraction of PAEs. Benefiting from the large surface area and high pore volume, the newly-synthesized CC-TPC based SPME method exhibited large enrichment factors (978-2210), low limits of detection (0.027-0.10 ng g ^- 1), satisfactory linear ranges (0.09-20 ng g ^- 1), acceptable repeatabilities (4.3-9.6%) and high relative recoveries (92.0-104.6%).

Analytical perspective and environmental remediation potentials of magnetic composite nanosorbents

The synthesis and application of magnetic nanosorbents to remove emerging pollutants have been considered the best environmental remediation and sustainability option. Incorporating magnetism shortens the treatment time and allows the sorbent to be recovered quickly using external magnetic with many cycles. The implementation of magnetic solid-phase extraction (MSPE) using magnetic materials of different shapes, sizes, and surface morphology can be a valuable tool in applying materials to prepare analytical samples. In MSPE applications, materials with strong magnetic domain can be used as precursors for constructing magnetic composite as a promising sorbent. This article focuses on the most recent and exceptional applications of magnetic adsorbents for preconcentration and removal purposes. Magnetic adsorbents, such as nanoparticles (NPs), foam, sponges, nanocomposites, hydrogels, and beads with multifunctional attributes have been comprehensively studied in terms of preparation procedures, limitations, advantages, and interactions between pollutants and magnetic composites. The role of magnetic sorbents in sample preparation methods, such as simple solid-phase extraction and microextraction, as well as sorptive extraction using a stir bar, was also examined. The use of magnetic adsorbents with analytical techniques, such as solid-phase extraction and solid-phase microextraction improves the method for preparing samples concerning the influential role of magnetic adsorbents. Towards the end, promising features and future outlook are also directed.

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.

Carbon Dot-Decorated Graphite Carbon Nitride Composites for Enhanced Solid-Phase Microextraction of Chlorobenzenes from Water

In this work, carbon dot-decorated graphite carbon nitride composites (CDs/g-C₃N₄) were synthesized and innovatively used as a SPME coating for the sensitive determination of chlorobenzenes (CBs) from water samples, coupled with gas chromatography-mass spectrometry. The CDs/g-C₃N₄ coating presented superior extraction performance in comparison to pristine g-C₃N₄, owing to the enhancement of active groups by CDs. The extraction capacities of as-prepared SPME coatings are higher than those of commercial coatings due to the functions of nitrogen-containing and oxygen-containing group binding, π-π stacking, and hydrophobic interactions. Under optimized conditions, the proposed method exhibits a wide linearity range (0.25-2500 ng L^-1), extremely low detection of limits (0.002-0.086 ng L^-1), and excellent precision, with relative standard deviations of 5.3-9.7% for a single fiber and 7.5-12.6% for five fibers. Finally, the proposed method was successfully applied for the analysis of CBs from real river water samples, with spiked recoveries ranging from 73.4 to 109.1%. This study developed a novel and efficient SPME coating material for extracting organic pollutants from environmental samples.

Amino-based covalent organic frameworks for a wide range of functional modification

A versatile protocol for modification of amino-based COFs with desired functionalities was developed via transforming the unreachable amino groups into imine, thiourea, amide and azo-based functional groups.