Effective Enrichment and Detection of Trace Polycyclic Aromatic Hydrocarbons in Food Samples based on Magnetic Covalent Organic Framework Hybrid Microspheres

The present study reported a facile, sensitive, and efficient method for enrichment and determination of trace polycyclic aromatic hydrocarbons (PAHs) in food samples by employing new core-shell nanostructure magnetic covalent organic framework hybrid microspheres (Fe₃O₄@COF-(TpBD)) as the sorbent followed by HPLC-DAD. Under mild synthetic conditions, the Fe₃O₄@COF-(TpBD) were prepared with the retention of colloidal nanosize, larger specific surface area, higher porosity, uniform morphology, and supermagnetism. The as-prepared materials showed an excellent adsorption ability for PAHs, and the enrichment efficiency of the Fe₃O₄@COF-(TpBD) could reach 99.95%. The obtained materials also had fast adsorption kinetics and realized adsorption equilibrium within 12 min. The eluent was further analyzed by HPLC-DAD, and good linearity was observed in the range of 1-100 ng/mL with the linear correlation being above 0.9990. The limits of detection (S/N = 3) and limits of quantitation (S/N = 10) for 15 PAHs were in the range of 0.83-11.7 ng/L and 2.76-39.0 ng/L, respectively. For the application, the obtained materials were employed for the enrichment of trace PAHs in food samples and exhibited superior enrichment capacity and excellent applicability.

A versatile covalent organic framework-based platform for sensing biomolecules

We herein report the design of a versatile covalent organic framework (COF)-based platform for sensing biomolecules. As a proof of concept, a highly sensitive and selective COF-based fluorescence turn-on detection of DNA and adenosine 5'-triphosphate is demonstrated.

Advances in covalent organic frameworks in separation science

Covalent organic frameworks (COFs) are a new class of multifunctional crystalline organic polymer constructed with organic monomers via robust covalent bonds. The unique properties such as convenient modification, low densities, large specific surface areas, good stability and permanent porosity make COFs great potential in separation science. This review shows the state-of-the art for the application of COFs and their composites in analytical separation science. COFs and their composites have been explored as promising sorbents for solid phase extraction, potential coatings for solid phase microextraction, and novel stationary phases for gas chromatography, high-performance liquid chromatography and capillary electrochromatography. The prospects of COFs for separation science are also presented, which can offer an outlook and reference for further study on the applications of COFs.

Hybridization of MOFs and COFs: A New Strategy for Construction of MOF@COF Core-Shell Hybrid Materials

The exploration of new porous hybrid materials is of great importance because of their unique properties and promising applications in separation of materials, catalysis, etc. Herein, for the first time, by integration of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), a new type of MOF@COF core-shell hybrid material, i.e., NH₂ -MIL-68@TPA-COF, with high crystallinity and hierarchical pore structure, is synthesized. As a proof-of-concept application, the obtained NH₂ -MIL-68@TPA-COF hybrid material is used as an effective visible-light-driven photocatalyst for the degradation of rhodamine B. The synthetic strategy in this study opens up a new avenue for the construction of other MOF-COF hybrid materials, which could have various promising applications.

Layer-by-layer preparation of 3D covalent organic framework/silica composites for chromatographic separation of position isomers

A layer-by-layer approach was developed to fabricate COF-300@SiO₂ for HPLC separation of position isomers.

A Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic Frameworks

Developing synthetic methodology to crystallize extended covalent structures has been an important pursuit of reticular chemistry. Here, we report a homogeneous synthetic route for imine covalent organic frameworks (COFs) where crystallites emerge from clear solutions without forming amorphous polyimine precipitates. The key feature of this route is the utilization of tert-butyloxycarbonyl group protected amine building blocks, which are deprotected in situ and gradually nucleate the crystalline framework. We demonstrate the utility of this approach by crystallizing a woven covalent organic framework (COF-112), in which covalent organic threads are interlaced to form a three-dimensional woven framework. The homogeneous imine COF synthesis also enabled the control of nucleation and crystal growth leading to uniform nanocrystals, through microwave-assisted reactions, and facile preparation of oriented thin films.

Self-assembling covalent organic framework functionalized magnetic graphene hydrophilic biocomposites as an ultrasensitive matrix for N-linked glycopeptide recognition

The development of additional functions and applications of covalent organic framework (COF)-derived materials still remains highly desired. In our work, a novel COF-functionalized magnetic graphene biocomposite (MagG@COF-5) was first developed as an ultrasensitive hydrophilic matrix via a facile self-assembly method for efficiently recognizing N-linked glycopeptides. By integrating the characteristics of the magnetic graphene and COF-5 layer, the MagG@COF-5 owns features of an outstanding magnetic response, a high specific area, strong hydrophilic properties and a unique size-exclusion effect. Accordingly, the MagG@COF-5 biocomposite showed excellent performance in N-linked glycopeptide analysis with a low detection limit (0.5 fmol μL^-1), an excellent size-exclusion effect (HRP digests/BSA, 1 : 600), good recyclability and reusability. More excitingly, the practical applicability of the biocomposite was evaluated by treatment with human serum (1 μL), in which 232 N-linked glycopeptides from 85 glycoproteins were detected. All the results demonstrate that the as-synthesized MagG@COF-5 biocomposite has huge potential for use in glycoproteome and clinical diagnosis fields. It will also open up new phases for application of COF-based materials.

Facile synthesis of core–shell structured magnetic covalent organic framework composite nanospheres for selective enrichment of peptides with simultaneous exclusion of proteins

Core–shell structured Fe₃O₄@TbBd composite nanospheres were synthesised using a facile approach and successfully applied for selective enrichment of peptides with simultaneous exclusion of proteins.

Facile synthesis of magnetic covalent organic frameworks for the hydrophilic enrichment of N-glycopeptides

Magnetic covalent organic frameworks were synthesized as novel hydrophilic materials for specific enrichment of glycopeptides.

High-performance adsorption and separation of anionic dyes in water using a chemically stable graphene-like metal–organic framework

MOF BUC-17 was used to conduct efficiently selective uptake of organic dyes, and achieve rapid separation of CR and MB from their mixture.