A fluorescent covalent organic framework for visual detection of p-benzoquinone

Covalent organic frameworks (COFs) as carrier for improved drug delivery and biosensing applications

Porous organic frameworks (POFs) represent a significant subclass of nanoporous materials in the field of materials science, offering exceptional characteristics for advanced applications. Covalent organic frameworks (COFs), as a novel and intriguing type of porous material, have garnered considerable attention due to their unique design capabilities, diverse nature, and wide-ranging applications. The unique structural features of COFs, such as high surface area, tuneable pore size, and chemical stability, render them highly attractive for various applications, including targeted and controlled drug release, as well as improving the sensitivity and selectivity of electrochemical biosensors. Therefore, it is crucial to comprehend the methods employed in creating COFs with specific properties that can be effectively utilized in biomedical applications. To address this indispensable fact, this review paper commences with a concise summary of the different methods and classifications utilized in synthesizing COFs. Second, it highlights the recent advancements in COFs for drug delivery, including drug carriers as well as the classification of drug delivery systems and biosensing, encompassing drugs, biomacromolecules, small biomolecules and the detection of biomarkers. While exploring the potential of COFs in the biomedical field, it is important to acknowledge the limitations that researchers may encounter, which could impact the practicality of their applications. Third, this paper concludes with a thought-provoking discussion that thoroughly addresses the challenges and opportunities associated with leveraging COFs for biomedical applications. This review paper aims to contribute to the scientific community's understanding of the immense potential of COFs in improving drug delivery systems and enhancing the performance of biosensors in biomedical applications.

A "turn-on" fluorescent sensor based on three-component covalent organic framework for trace water detection

Trace amount of H2O is difficult to eliminate in laboratory environments and chemical industries as impurities. In some chemical reactions, trace amount of H2O can alter final reaction products, yield, and selectivity. So, the detection of trace H2O is very important. Herein, a series of TFPT[X]-BMTH- covalent organic frameworks (COFs) (X = 0, 33, 50, 67, 100 %) with intramolecular charge transfer effect (ICT) and aggregate-induced emission (AIE) characteristics were synthesized by amino-aldehyde condensation reaction between 2,5-bis(2-methoxyethoxy)terephthalohydrazide (BMTH)/ 1,3,5-tris(p-formylphenyl)benzene (TFPB) and 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde (TFPT). By changing TFPT' content in TFPT[X]-BMTH-COFs, the ICT and AIE of TFPT[X]-BMTH-COFs can be controlled, and accordingly the response to trace H2O can be adjusted. A H2O sensor based on TFPT[67]-BMTH-COF with a wide linear range from 0 wt% to 0.5 wt% was developed and the detection limit was 0.00007 wt%. In addition, a portable fluorescent test paper based on TFPT[67]-BMTH-COF for visual detection of trace H2O in honey samples and salt was constructed. This work has important guiding significance for the development of fluorescent probes for the visual detection of trace water.

Post-synthetic modifications of covalent organic frameworks (COFs) for diverse applications

Covalent organic frameworks (COFs) are porous and crystalline organic polymers, which have found usage in various fields. These frameworks are tailorable through the introduction of diverse functionalities into the platform. Indeed, functionality plays a key role in their different applications. However, sometimes functional groups are not compatible with reaction conditions or can compete and interfere with other groups of monomers in the direct synthetic method. Also, pre-synthesis of bulky moieties in COFs can negatively affect crystal formation. To avoid these problems a post-synthetic modification (PSM) approach is a helpful tactic. Also, with the assistance of this strategy porous size can be tunable and stability can be improved without considerable effect on the crystallite. In addition, conductivity, hydrophobicity/ hydrophilicity, and chirality are among the features that can be reformed with this method. In this review, different types of PSM strategies based on recent articles have been divided into four categories: (i) post-functionalization, (ii) post-metalation, (iii) chemical locking, and (iv) host-guest post-modifications. Post-functionalization and chemical locking methods are based on covalent bond formation while in post-metalation and host-guest post-modifications, non-covalent bonds are formed. Also, the potential of these post-modified COFs in energy storage and conversion (lithium-sulfur batteries, hydrogen storage, proton-exchange membrane fuel cells, and water splitting), heterogeneous catalysts, food safety evaluation, gas separation, environmental domains (greenhouse gas capture, radioactive element uptake, and water remediation), and biological applications (drug delivery, biosensors, biomarker capture, chiral column chromatography, and solid-state smart nanochannels) have been discussed.