Advances in covalent organic frameworks in separation science

Applications of Dynamic Covalent Chemistry Concept towards Tailored Covalent Organic Framework Nanomaterials: A Review

Covalent organic frameworks (COFs) are a rapidly developing class of materials that has been of immense research interest during the last ten years. Numerous reviews have been devoted to summarizing the synthesis and applications of COFs. However, the underlying dynamic covalent chemistry (DCC), which is the foundation of COFs synthesis, has never been systematically reviewed in this context. Dynamic covalent chemistry is the practice of using thermodynamic equilibriums to molecular assemblies. This Critical Review will cover the state-of-the-art use of DCC to both synthesize COFs and expand the applications of COFs. Five synthetic strategies for COF synthesis are rationalized, namely: modulation, mixed linker/linkage, sub-stoichiometric reaction, framework isomerism, and linker exchange, which highlight the dynamic covalent chemistry to regulate the growth and to modify the properties of COFs. Furthermore, the challenges in these approaches and potential future perspectives in the field of COF chemistry are also provided.

Covalent Organic Frameworks in Sample Preparation

Covalent organic frameworks (COFs) can be classified as emerging porous crystalline polymers with extremely high porosity and surface area size, and good thermal stability. These properties have awakened the interests of many areas, opening new horizons of research and applications. In the Analytical Chemistry field, COFs have found an important application in sample preparation approaches since their inherent properties clearly match, in a good number of cases, with the ideal characteristics of any extraction or clean-up sorbent. The review article is meant to provide a detailed overview of the different COFs that have been used up to now for sample preparation (i.e., solid-phase extraction in its most relevant operational modes-conventional, dispersive, magnetic/solid-phase microextraction and stir-bar sorptive extraction); the extraction devices/formats in which they have been applied; and their performances and suitability for this task.

Covalent Organic Frameworks: Emerging Organic Solid Materials for Energy and Electrochemical Applications

Covalent organic frameworks (COFs), materials constructed from organic building blocks joined by robust covalent bonds, have emerged as attractive materials in the context of electrochemical applications because of their high, intrinsic porosities and crystalline frameworks, as well as their ability to be tuned across two- and three-dimensions by the judicious selection of building blocks. Because of the recent and rapid development of this field, we have summarized COFs employed for electrochemical applications, such as batteries and capacitors, water splitting, solar cells, and sensors, with an emphasis on the structural design and resulting performance of the targeted electrochemical system. Overall, we anticipate this review will stimulate the design and synthesis of the next generation of COFs for use in electrochemical applications and beyond.

Solid-phase microextraction using a β-ketoenamine-linked covalent organic framework coating for efficient enrichment of synthetic musks in water samples

Covalent organic frameworks with tunable porous crystallinity and outstanding stability have recently exhibited fascinating pretreatment performance as solid-phase microextraction coatings. In this report, a β-ketoenamine-linked covalent organic framework (TpPa-1) was successfully constructed through a Schiff-base-type reaction between 1,3,5-triformylphloroglucinol (Tp) and para-phenylenediamine (Pa-1). A TpPa-1 coating was then fabricated on a stainless-steel fiber for capturing trace synthetic musks. This TpPa-1 coating exhibited strong interaction with synthetic musks because of its hydrophobicity and π-π affinity. This TpPa-1-based solid-phase microextraction methodology, coupled with gas chromatography-tandem mass spectrometry, provided high enrichment factors (1214-12 487), wide linearity (0.5-1000 ng L-1), low limits of detection (0.04-0.31 ng L-1), and acceptable reproducibility (relative standard deviation, <10%) for nine synthetic musks. Recoveries at three spiked levels in three types of water samples were between 76.2% and 118.7%. These results indicated the promising applicability of the TpPa-1 as a solid-phase microextraction fiber coating for reliably detecting trace concentrations of synthetic musks in the environment.

Room-temperature preparation of a chiral covalent organic framework for the selective adsorption of amino acid enantiomers

Herein, we have reported the facile room-temperature synthesis of a chiral covalent organic framework (CCOF) for the enantioselective adsorption of amino acids. The prepared CCOF provides various stereoscopic interactions with amino acids for highly selective adsorption of their enantiomers.

Covalent organic frameworks for separation applications

Covalent organic frameworks (COFs) are an emerging class of crystalline porous polymers with highly tuneable structures and functionalities. COFs have been proposed as ideal materials for applications in the energy-intensive field of molecular separation due to their notable intrinsic features such as low density, exceptional stability, high surface area, and readily adjustable pore size and chemical environment. This review attempts to highlight the key advancements made in the synthesis of COFs for diverse separation applications such as water treatment or the separation of gas mixtures and organic molecules, including chiral and isomeric compounds. Methods proposed for the fabrication of COF-based columns and continuous membranes for practical applications are also discussed in detail. Finally, a perspective regarding the remaining challenges and future directions for COF research in the field of separation has also been presented.

A functionalized magnetic covalent organic framework for sensitive determination of trace neonicotinoid residues in vegetable samples

A functionalized magnetic covalent organic framework containing the nitro groups (Fe₃O₄@COF-(NO₂)₂) with core-shell structure was synthesized for magnetic solid phase extraction (MSPE) of six neonicotinoid insecticides residue in vegetable samples. The structure of Fe₃O₄@COF-(NO₂)₂ was investigated by various characterization techniques. The Fe₃O₄@COF-(NO₂)₂ exhibits the excellent thermal and chemical stability, high surface area (254.72 m² g^-1), total pore volume (0.19 cm³ g^-1), high magnetic responsivity (27.7 emu g^-1), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A sensitive method was developed by using Fe₃O₄@COF-(NO₂)₂-based MSPE coupled with HPLC with UV detection. It offered good linearity within the range of 0.1-30 ng mL^-1, low limits of detection (S/N = 3) of 0.02-0.05 ng mL^-1. Furthermore, high enrichment factors of 170-250 for six neonicotinoid insecticides were obtained. The applicability of Fe₃O₄@COF-(NO₂)₂ is demonstrated for measuring trace neonicotinoid residues in vegetable samples with satisfactory recoveries, which ranged from 77.5 to 110.2%. The results indicated that the Fe₃O₄@COF-(NO₂)₂ microspheres offer great potential for efficient extraction of neonicotinoid insecticides from complex samples.

Ultrasound-assisted synthesis of clover-shaped nano-titania functionalized covalent organic frameworks for the dispersive solid phase extraction of N-nitrosamines in drinking water

In this study, three batches of nano-titania functionalized covalent organic frameworks were acquired depending on different solvothermal reaction stages (24 h, 48 h and 72 h), which were named as single roll-up shaped nano-titania functionalized COFs (SSTF-COFs), double roll-up shaped nano-titania functionalized COFs (DSTF-COFs) and clover-shaped nano-titania functionalized covalent organic framework (CSTF-COFs), respectively. After comparing their extraction performances, the more efficient and stable CSTF-COFs were selected as sorbent for the dispersive solid phase extraction (dSPE) of eight target N-nitrosamines in drinking water, followed by the determination with liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). Owing to the introduction of hydroxy groups, CSTF-COFs showed high extraction efficiency for N-nitrosamines with a wide range of polarities through hydrogen bonding interaction, hydrophobic interaction and hydrophilic interaction. Under optimum conditions, the developed method provided relatively low limits of detection (0.13-2.45 ng/L) and satisfactory recoveries (88.6-105.5%), with relative standard deviations (RSDs) less than 8.3%. Therefore, with the assistance of CSTF-COFs, trace levels of N-nitrosamines were quantitatively and sensitively determined in 31 out of 460 bottled drinking water samples in a sensitive and convenient way.

Exploration of a novel triazine-based covalent organic framework for solid-phase extraction of antibiotics

A novel COF was synthesized, which has a similar structure to SNW-1 but different selectivity towards antibiotics.

Controlled Fabrication of Silica@Covalent Triazine Polymer Core-Shell Spheres as a Reversed-Phase/Hydrophilic Interaction Mixed-Mode Chromatographic Stationary Phase

The unique properties of covalent triazine-based organic framework/polymers, including large surface area, hydrophilic-lipophilic-balanced adsorption, and economical preparation, make it a promising candidate as a stationary phase for high-performance liquid chromatography. However, irregular shapes and wide size distributions of such particles hinder column packing, resulting in a low column efficiency or a high back pressure. Herein, we describe the fabrication of SiO₂@ covalent triazine-based organic polymer (CTP) core-shell microspheres with a distinct sphere-coating-sphere appearance using aminosilica as the supporting substrate to grow the CTP shell. By adjusting the amount of reactants, the thickness of the CTP shell, which consists of triazine and 1,3,5-triphenylbenzene monomers, was easily controlled. The developed core-shell microspheres were characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, solid-state ¹³C nuclear magnetic resonance analysis, and N₂ adsorption experiments. The synergism of the triazine and aromatic moieties on CTP provides the new stationary phase with multiple retention mechanisms, including hydrophobic, π-π, electron donor-acceptor, hydrogen-bonding interactions, and so forth. On the basis of these interactions, successful separation and higher shape selectivity were achieved among several analytes that vary in polarity under both reversed-phase and hydrophilic interaction liquid chromatography conditions. Therefore, SiO₂@CTP microspheres combine the advantages of good column packing properties of the uniform monodisperse silica microspheres and the recognition performance of CTP, generating flexible selectivity and application prospect for both hydrophilic and hydrophobic analytes.

Thiol-Ene Click Synthesis of Phenylboronic Acid-Functionalized Covalent Organic Framework for Selective Catechol Removal from Aqueous Medium

We report a thiol-ene click strategy for the preparation of a novel phenylboronic acid-functionalized covalent organic framework (COF) for selective removal of catechol in aqueous solution. Vinyl-functionalized 2,5-diallyloxyterephthalaldehyde (Da-V) was prepared as a building ligand. Da-V was then condensed with 1,3,5-tris(4-aminophenyl)benzene (Tab) to give a vinyl-functionalized COF DhaTab-V. Subsequently, 4-mercaptophenylboronic acid (4-MPBA) was covalently linked on DhaTab-V via thiol-ene click reaction to give phenylboronic acid-functionalized COF DhaTab-PBA. The adsorption isotherms, energetics and kinetics, and reusability of DhaTab-PBA for the adsorption and removal of catechol from aqueous solution were investigated in detail. This phenylboronic acid-functionalized COF is promising as sorbent for selective removal of catechol from aqueous medium with large adsorption capacity and good reusability.

Recent advances in the construction of functionalized covalent organic frameworks and their applications to sensing

Covalent organic frameworks (COFs), as an emerging class of porous crystalline polymers, are built by the combination of the light elements through the strong covalent bonds. In the past decade, COFs have been reported to show plenty of unique properties (such as ordered channels, large specific surface area, highly tunable porosity, optional building blocks, predictable and stable structure, and abundant functional groups), and have been widely applied in multiple fields. Recently, to further improve the potential performances of COFs and extend their applicability, a number of COFs with various functionalities have been successfully developed through the functionalization modification. In this review, we summarized the advanced design and construction of functionalized COFs, including COFs with post-synthetic modification, COFs-based composites (e.g. COFs-metal nanoparticles composites, COFs-metal oxide nanoparticles composites, COFs-MOFs composites, and COFs-enzyme composites), and molecularly imprinted COFs. Impressively, the applications of functionalized COFs to sensing also have been comprehensively summarized, including colorimetric sensing, fluorescent sensing, electrochemical sensing, and other sensing (such as quartz crystal microbalance (QCM) sensing, photoelectrochemical sensing, and humidity sensing). In the end, future opportunities and challenges in this promising field are tentatively proposed.

Ambient temperature fabrication of a covalent organic framework from 1,3,5-triformylphloroglucinol and 1,4-phenylenediamine as a coating for use in open-tubular capillary electrochromatography of drugs and amino acids

A covalent organic framework (COF) named TpPa-1 was designed and synthesized at ambient temperature by an ultrasound-assisted method from 1,3,5-triformylphloroglucinol (Tp) and 1,4-phenylenediamine (Pa-1). It was utilized as a stationary phase in open-tubular capillary electrochromatography (OT-CEC). The column was coated with TpPa-1 using a covalent bonding strategy. The coated capillary was characterized by morphology, crystallography, and mesoporous analysis to confirm the successful fabrication. The OT-CEC method was utilized for the analysis of tetracyclines, sulfonamides, cephalosporins and amino acids with high-resolution (Rs > 1.81) and good precision (RSD < 4.9%). It takes about 12 h from COF preparation to OT-CEC separation. Graphical abstract A covalent organic framework (COF) named TpPa-1 was synthesized at ambient temperature by an ultrasound-assisted method from 1,3,5-triformylphloroglucinol (Tp) and 1,4-phenylenediamine (Pa-1). COF-TpPa-1 modified capillary column was utilized for the analysis of tetracyclines, sulfonamides, cephalosporins and amino acids with high-resolution and good precision.

Facile magnetization of covalent organic framework for solid-phase extraction of 15 phthalate esters in beverage samples

Phthalate esters (PAEs), a category of widely used plasticizers, are tend to migrate from plastic packaging to drinks. In this paper, we develop a simple and rapid coprecipitation method for synthesis of a magnetic covalent organic framework (COF) adsorbent. The fabricated COF-(TpBD)/Fe₃O₄ was applied to magnetic solid phase extraction (MSPE) of 15 phthalate esters (PAEs) for subsequent GC-MS/MS determination in beverage samples. The as-synthesized magnetic adsorbent exhibited great potential in PAEs analysis with a limit of detection of 15 PAEs ranged from 0.005 to 2.748 μg L^-1 (S/N = 3). The intra-day and inter-day relative standard deviations (RSD) value of the PAEs were less than 8.8% and 9.9%, respectively. The adsorbent can be reused after washing with methanol. The developed method was successfully applied for the determination of trace PAEs in eight beverages with recoveries ranging from 79.3% to 121.8% and RSDs were less than 11.9%. This work provides a simple magnetization process, which facilitates the application of COFs for enrichment and separation of PAEs in beverages with different matrices.

Well-Defined Materials for High-Performance Chromatographic Separation

Chromatographic separation has been widely applied in various fields, such as chemical engineering, precision medicine, energy, and biology. Because chromatographic separation is based on differential partitioning between the mobile phase and stationary phase and affected by band dispersion and mass transfer resistance from these two phases, the materials used as the stationary phase play a decisive role in separation performance. In this review, we discuss the design of separation materials to achieve the separation with high efficiency and high resolution and highlight the well-defined materials with uniform pore structure and unique properties. The achievements, recent developments, challenges, and future trends of such materials are discussed. Furthermore, the surface functionalization of separation ma-terials for further improvement of separation performance is reviewed. Finally, future research directions and the challenges of chromatographic separation are presented.

Covalent organic framework incorporated chiral polymer monoliths for capillary electrochromatography

A covalent organic framework, Schiff base network-1 (SNW-1), was synthesized and incorporated into cellulase based poly(glycidyl methacrylate-co-ethylene dimethacrylate) (cellulase@poly(GMA-EDMA-SNW-1)) monolith to afford a novel chiral stationary phase for capillary electrochromatography (CEC). SNW-1 is attractive as a stationary phase for CEC because it not only features high surface areas but also provides conjugate structures and abundant amine groups to give π-π electrostatic stacking and hydrogen bonding property. Incorporation of SNW-1 into monolithic column could improve the column efficiency and increase the interactions between the tested racemates and the stationary phase thus significantly improved their CEC separation. The obtained monoliths were characterized by scanning electron microscopy, elemental analysis and nitrogen adsorption. Moreover, effects of SNW-1 concentration, immobilization pH of cellulase and CEC conditions were also investigated. Under the optimized conditions, the cellulase@poly(GMA-EDMA-SNW-1) monolith exhibited excellent enantioseparation performance for eight pairs of different classes of chiral drugs including β-blockers, antihistamines and anticoagulants. Satisfactory repeatability was achieved with relative standard deviations for intra-day, inter-day and column-to-column runs less than 4.5%, and batch-to-batch runs less than 6.8%. The experiment results reveal that the combination of the versatile features of monoliths and unique properties of SNW-1 could be a promising strategy for chiral separation.

Recent advances on porous organic frameworks for the adsorptive removal of hazardous materials

Environmental pollution is one of the most serious problems facing mankind today, and has attracted widespread attention worldwide. The burgeoning class of crystalline porous organic framework materials, metal-organic frameworks and covalent organic frameworks present promising application potential in areas related to pollution control due to their interesting surface properties. In this review, the literature of the past five years on the adsorptive removal of various hazardous materials, mainly including heavy metal ions, harmful gases, organic dyes, pharmaceutical and personal care products, and radionuclides from the environment by using COFs and MOFs, is summarized. The adsorption mechanisms are also discussed to help understand their adsorption performance and selectivity. Additionally, some insightful suggestions are given to enhance the performance of MOFs and COFs in the adsorptive removal of various hazardous materials.

Fast Desalination by Multilayered Covalent Organic Framework (COF) Nanosheets

Covalent organic frameworks (COFs) are penetrated with uniform and ordered nanopores, implying their great potential in molecular/ion separations. As an imine-linked, stable COF, TpPa-1 is receiving tremendous interest for molecular sieving membranes. Theoretically, atomically thin TpPa-1 monolayers exhibit extremely high water permeance but unfortunately no rejection to ions because of its large pore size (∼1.58 nm). The COF monolayers tend to stack to form laminated multilayers, but how this stacking influences water transport and ion rejections remains unknown. Herein, we investigate the transport behavior of water and salt ions through multilayered TpPa-1 COFs by nonequilibrium molecular dynamics simulations. By analyzing both the interfacial and interior resistance for water transport, we reveal that with rising stacking number of COF multilayers exhibit increasing ion rejections at the expense of water permeance. More importantly, stacking in the offset eclipsed fashion significantly reduces the equivalent pore size of COF multilayers to 0.89 nm, and ion rejection is correspondingly increased. Remarkably, 25 COF monolayers stacked in this fashion give 100% MgCl₂ rejection, whereas water permeance remains 1 to 2 orders of magnitude higher than that of commercial nanofiltration membranes. This work demonstrates the rational design of fast membranes for desalination by tailoring stacking number and fashion of the COF monolayers.

Facile construction of magnetic core-shell covalent organic frameworks as efficient solid-phase extraction adsorbents for highly sensitive determination of sulfonamide residues against complex food sample matrices

Integration of advanced sample pretreatment techniques, with the involvement of functional nano/micro-materials as adsorbents, is of great importance and value for food-safety precise inspection. For now, the major demands for functional adsorbents are ease of fabrication, fast adsorption and separation performance, low toxicity, robustness, and reusability. In the present work, core-shell structured magnetic covalent organic frameworks (COFs) that employed Fe3O4 microspheres as the magnetic core and TpBD COFs as the adsorption shell have been successfully constructed as efficient solid phase extraction (SPE) adsorbents for complex food sample analysis. In favor of the combination of magnetic separation and effective preconcentration, the proposed magnetic COF-SPE method gave a rapid detection performance of the simultaneous detection of ten sulfonamide residues as well as high sensitivity, with detection limits in the range of 0.28-1.45 μg L-1 under the optimized experimental conditions. The Fe3O4@TpBD core-shell adsorbents also demonstrated good stability, robust SPE preconcentration ability, excellent determination recovery, and good reusability. The applicability of the developed SPE method was well demonstrated by real sample analysis, with the recoveries ranging from 82-94%. Through this example, it was believed that the new emerging porous nano/micro-materials, like COFs, metal-organic networks, or hybrid structures, would play more and more important roles as functional materials in food-safety inspection, especially for highly efficient determination of targets against complicated food sample matrices.

Triazine-Based Covalent Organic Framework: A Promising Sorbent for Efficient Elimination of the Hydrocarbon Backgrounds of Organic Sample for GC-MS and 1H NMR Analysis of Chemical Weapons Convention Related Compounds

The strict monitoring and precise measurements of chemical warfare agents (CWAs) in environmental and other complex samples with high accuracy have great practical significance from the forensic and Chemical Weapons Convention (CWC) verification point of view. Therefore, this study was aimed to develop an efficient extraction and enrichment method for identification and quantification of toxic agents, especially with high sensitivity and multidetection ability in complex samples. It is the first study on solid-phase extraction (SPE) of CWAs and their related compounds from hydrocarbon backgrounds using covalent triazine-based frameworks (CTFs). This nitrogen-rich CTF sorbent has shown an excellent SPE performance toward sample cleanup by selective elimination of hydrocarbon backgrounds and enrich the CWC related analytes in comparison with the conventional and other reported methods. The best enrichment of the analytes was found with the washing solvent (1 mL of n-hexane) and the extraction solvent (1 mL of dichloromethane). Under the optimized conditions, the SPE method had good linearity in the concentration range of 0.050-10.0 μg mL^-1 for organophosphorus esters, 0.040-20.0 μg mL^-1 for nerve agents, and 0.200-20.0 μg mL^-1 for mustards with correlation coefficients ( r²) between 0.9867 and 0.9998 for all analytes. Limits of detection ( S/ N = 3:1) in the SIM mode were found to be in the range of 0.015-0.050 μg mL^-1 for organophosphorus esters, 0.010-0.030 μg mL^-1 for nerve agents, and 0.050-0.100 μg mL^-1 for blister agents. Limits of quantification ( S/ N = 10:1) were found in the range of 0.050-0.200 μg mL^-1 for organophosphorus esters, 0.040-0.100 μg mL^-1 for nerve agents, and 0.180-0.350 μg mL^-1 for blister agents in the SIM mode. The recoveries of all analytes ranged from 87 to 100% with the relative standard deviations ranging from 1 to 8%. This method was also successfully applied for the sample preparation of ¹H NMR analysis of sulfur and nitrogen mustards in the presence of hydrocarbon backgrounds. Therefore, this SPE method provides the single sample preparation for both NMR and GC-MS analyses.

Simultaneous determination of three sulfanilamide artificial sweeteners in foodstuffs by capillary electrophoresis coupled with contactless conductivity detection based on porous aromatic frameworks enhanced solid phase extraction

In this paper, a simple and easy method of solid phase extraction (SPE) followed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) is evaluated as a novel approach for the simultaneous determination of acesulfame-K (ACE), sodium saccharin (SAC), and sodium cyclamate (CYC) in foodstuffs without derivatization. To reduce the complex matrix interference resulting from the constituents of samples and enriched targets, porous aromatic frameworks (PAFs) enhanced SPE, a suitable sample pretreatment procedure, was introduced. Several factors affecting extraction efficiency and electrophoretic separation were investigated. Additionally, the interaction mechanisms between the host (PAF-6) and guests (ACE, SAC, and CYC) were studied. Under the optimum conditions, three sulfanilamide artificial sweeteners were baseline separated within 8 min, exhibiting a linear calibration over two orders of magnitude (R2 > 0.995). The limits of detection (LOD) and quantification (LOQ) were considered better than those usually obtained by CE with ultraviolet and C4D detection. The proposed SPE–CE–C4D method has been successfully applied to analyse beverage samples and candied fruits with recoveries in the range of 78.89%–92.00%.

BODIPY-Decorated Nanoscale Covalent Organic Frameworks for Photodynamic Therapy

Covalent organic frameworks (COFs), an emerging class of organic porous materials, have attracted intense attention due to their versatile applications. However, the deliberate fabrication of COF-based nanomaterials for nanomedical application remains challenging due to difficulty in their size- and structure-controlled synthesis and poor aqueous dispersibility. Herein, we report two boron-dipyrromethene (BODIPY)-decorated nanoscale COFs (NCOFs), which were prepared by the Schiff-base condensation of the free end -CHO (bonding defects in COFs) on the established imine-based NCOFs with the amino-substituted organic photosensitizer BODIPY via "bonding defects functionalization" approach. Thus BODIPY has been successfully nanocrystallized via the NCOF platform, and can be used for photodynamic therapy (PDT) to treat tumors. These NCOF-based PDT agents featured nanometer size (∼110 nm), low dark toxicity, and high phototoxicity as evidenced by in vitro and in vivo experiments. Moreover, the "bonding defects functionalization" approach might open up new avenues for the fabrication of additional COF-based platforms for biomedical treatment.

Covalent immobilization of covalent organic framework on stainless steel wire for solid-phase microextraction GC-MS/MS determination of sixteen polycyclic aromatic hydrocarbons in grilled meat samples

Covalent organic framework TpBD was grafted on stainless steel wire with polydopamine as a linker. The fabricated TpBD bonded stainless steel wire was used as the solid-phase microextraction fiber to extract sixteen polycyclic aromatic hydrocarbons (PAHs) for subsequent GC-MS/MS determination in grilled meat samples. The developed method gave the limits of detection (S/N = 3) from 0.02 (pyrene)-1.66 (naphthalene) ng L^-1 and enhancement factors from 1069 (naphthalene)-10879 (benz(a)anthracene). The relative standard deviations (RSDs) for intra-day and inter-day study are in the range of 2.6%-8.5% and 4.5%-9.4%, respectively. The fiber-to-fiber RSDs for three parallel prepared fibers were 5.3%-10.0%. One TpBD bonded fiber can stand at least 200 cycles without significant loss of extraction efficiency. The developed method was successfully applied for the determination of trace PAHs in grilled meat samples with recoveries from 85.1% to 102.8%.