Fabrication of covalent organic frameworks and its selective extraction of fluoronitrobenzenes from environmental samples

Covalent organic frameworks as highly versatile materials for the removal and electrochemical sensing of organic pollutants

The presence of persistent organic compounds in water has become a worldwide issue due to its resistance to natural degradation, inducing its environmental resilience. Therefore, the accumulation in water bodies, soils, and humans produces toxic effects. Also, low levels of organic pollutants can lead to serious human health issues, such as cancer, chronic diseases, thyroid complications, immune system suppression, etc. Therefore, developing efficient and economically viable remediation strategies motivates researchers to delve into novel domains within material science. Moreover, finding approaches to detect pollutants in drinking water systems is vital for safeguarding water safety and security. Covalent organic frameworks (COFs) are valuable materials constructed through strong covalent interactions between blocked monomers. These materials have tremendous potential in removing and detecting persistent organic pollutants due to their high adsorption capacity, large surface area, tunable porosity, porous structure, and recyclability. This review discusses various synthesis routes for constructing non-functionalized and functionalized COFs and their application in the remediation and electrochemical sensing of persistent organic compounds from contaminated water sources. The development of COF-based materials has some major challenges that need to be addressed for their suitability in the industrial configuration. This review also aims to highlight the importance of COFs in the environmental remediation application with detailed scrutiny of their challenges and outcomes in the current research scenario.

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.

Capillary coated with three-dimensional covalent organic frameworks for separation of fluoroquinolones by open-tubular capillary electrochromatography

The Schiff-base reaction of 1,3,5-triformylphloroglucinol (Tp) and tetra(4-aminophenyl)methane (TAM) was performed for the synthesis of a three-dimensional covalent organic framework named 3D TpTAM, which was obtained by an ultrasound-assisted method for the first time. The morphology and structure of the synthesized TpTAM were characterized through various methods. Then, TpTAM-coated capillary columns were subsequently prepared by a covalent bonding method within a short time and applied for the separation of fluoroquinolones by capillary electrochromatography (CEC) with good resolution and reproducibility. The intraday relative standard deviations (RSDs) of the retention time and peak areas were 0.88%-0.95% and 2.27%-3.81%, respectively. The interday RSDs of retention time and peak areas were 0.71%-0.89% and 0.88%-3.60%, respectively. The column-to-column RSDs of retention time and peak areas were less than 1.90% and 13.56%, respectively. The interbatch RSDs of retention time and peak areas were less than 3.48% and 3.89%, respectively. The TpTAM-coated capillary columns could be used for no less than 100 runs with no observable changes in the separation efficiency. The separation mechanism was also studied, which indicated that π-π stacking effects, hydrophobic interactions and hydrogen bonding were the main factors. The results revealed that 3D TpTAM should have superior potential as the stationary phase in CEC for chromatographic separation.

Covalent organic framework-LZU1@PEI@Fe3O4-based magnetic dispersive micro-solid phase extraction of tetracyclines from environmental water prior to HPLC analysis

In this work, COF-LZU1@PEI@Fe₃O₄ was synthesized by immobilization of COF-LZU1 onto the surface of polyethyleneimine-functionalized Fe₃O₄ nanoparticles (PEI@Fe₃O₄) and employed as an adsorbent for magnetic dispersive micro-solid phase extraction of tetracyclines (TCs). COF-LZU1@PEI@Fe₃O₄ was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and nitrogen adsorption-desorption isotherms analysis. The optimal extraction and desorption conditions were as follows: 15.00 mL sample solution (pH 7.0) extracted with 5.0 mg of adsorbent for 30 min at 30 °C, and then desorbed with 1.50 mL methanol/acetonitrile/0.02 mol L^-1 oxalic acid solution (v/v, 1 : 2 : 7). Good linearities were obtained between the peak area and TC concentration ranging from 5-500 μg L^-1 with correlation coefficients (R²) higher than 0.9992 and limits of detection lower than 0.51 μg L^-1. The relative standard deviations (RSDs) of intra-day and inter-day were less than 5.7% and 7.4%, respectively. The developed method was successfully applied to the determination of TCs in environmental water samples with recoveries in the range of 87.0-113.8% and RSDs less than 5.1%, suggesting great potential of COF-LZU1@PEI@Fe₃O₄ for efficient extraction and analysis of trace TCs in water samples.