The Origin of the Reproduction of Different Nitrogen Uptakes in Covalent Organic Frameworks (COFs)

A review of recent advancement in covalent organic framework (COFs) synthesis and characterization with a focus on their applications in antibacterial activity

The primary objective of this review is to present a comprehensive examination of the synthesis, characterization, and antibacterial applications of covalent organic frameworks (COFs). COFs represent a distinct category of porous materials characterized by a blend of advantageous features, including customizable pore dimensions, substantial surface area, and adaptable chemical properties. These attributes position COFs as promising contenders for various applications, notably in the realm of antibacterial activity. COFs exhibit considerable potential in the domain of antibacterial applications, owing to their amenability to functionalization with antibacterial agents. The scientific community is actively exploring COFs that have been imbued with metal ions, such as copper or silver, given their observed robust antibacterial properties. These investigations strongly suggest that COFs could be harnessed effectively as potent antibacterial agents across a diverse array of applications. Finally, COFs hold immense promise as a novel class of materials for antibacterial applications, shedding light on the synthesis, characterization, and functionalization of COFs tailored for specific purposes. The potential of COFs as effective antibacterial agents beckons further exploration and underscores their potential to revolutionize antibacterial strategies in various domains.

Effect of interlayer slipping on the geometric, thermal and adsorption properties of 2D covalent organic frameworks: a comprehensive review based on computational modelling studies

Two-dimensional covalent organic frameworks (2D-COFs) are a class of crystalline porous organic polymers, consisting of 2D-planar sheets stacked together perpendicularly via noncovalent forces. Since their discovery, 2D-COFs have attracted extensive attention for optoelectronic and adsorption applications. Owing to the layer stacking nature of 2D COFs, various new slipped structures that are energetically favourable can be designed. These interlayer slipped structures are actively responsible for tuning (mostly enhancing) the optoelectronic properties, thermal properties, and mechanical strength of 2D COFs. This review summarizes the effect of interlayer slipping on the energetic stability, electronic behaviour and gas adsorption properties of 2D layered COFs, which is explained through computational modelling simulations. Since computational modelling offers a deep insight into electronic behaviour at the atomic scale, which is potentially impossible through experimental techniques, the introduction and role of computational techniques in such studies have also been described.

High-Throughput Computational Screening of Two-Dimensional Covalent Organic Frameworks (2D COFs) for Capturing Radon in Moist Air

Radon (Rn) and its decay products are the primary sources of natural ionizing radiation exposure for the public, posing significant health risks, including being a leading cause of lung cancer. Porous material-based adsorbents offer a feasible and efficient solution for controlling Rn concentrations in various scenes to achieve safe levels. However, due to competitive adsorption between Rn and water, finding candidates with a higher affinity and capacity for capturing Rn in humid air remains a significant challenge. Here, we conducted high-throughput computational screening of 8641 two-dimensional covalent organic frameworks (2D COFs) in moist air using grand canonical Monte Carlo simulations. We identified the top five candidates and revealed the structure-performance relationship. Our findings suggest that a well-defined cavity with an approximate spherical inner space, with a diameter matching that of Rn, is the structural basis for a proper Rn capturing site. This is because the excellent steric match between the cavity and Rn maximizes their van der Waals dispersion interactions. Additionally, the significant polarization electrostatic potential surface of the cavity can regulate the adsorption energy of water and ultimately impact Rn selectivity. Our study offers a potential route for Rn management using 2D COFs in moist air and provides a scientific basis for further experimentation.

Eu3+-β-diketone functionalized covalent organic framework hybrid material as a sensitive and rapid response fluorescent sensor for glutaraldehyde

A covalent organic framework (named as TpDq) linked by β-ketoamine was prepared by imine condensation reaction with 1,3,5-triformylphloroglucinol (TFP) and 2,6-diaminoanthraquinone (DAAQ) as building blocks. Via employing a functionalized modification strategy, a new lanthanide complex Eu³⁺-β-diketone functionalized covalent organic framework hybrid material, Eu-TTA@TpDq (TTA = 2-thenoyltrifluoroacetone), has been synthesized. After post-synthetic modification (PSM), the shape and structure of the parent framework is well preserved and the modified material shows remarkable luminescence properties. Based on this, we designed it as a fluorescent probe and tried to use it to sense common aldehydes. The results indicate that Eu-TTA@TpDq exhibits a turn-off response toward glutaraldehyde which can distinguish from other common aldehydes. The fluorescent probe has the advantages of reusability, pH stability (4.50-8.52), fast luminescence response (<1 min) and low detection limit. The linear range of this method was 0-100 μM; the detection limit was 4.55 μM; the relative standard deviation was 2.16%. Furthermore, it has broad application prospect in both practical sensing of glutaraldehyde in water environment and simple detection of glutaraldehyde vapor. In addition, we preliminarily discussed the possible sensing mechanism.

Judicious design functionalized 3D-COF to enhance CO2 adsorption and separation

The effects of functional groups (including OH, OCH₃ , NH₂ , CH₂ NH₂ , COOH, SO₃ H, OCO(CH₂ )₂ COOH(E-COOH), and (CH₂ )₄ COOH(c-COOH)) in 3D covalent organic frameworks (3D-COFs) on CO₂ adsorption and separation are investigated by grand canonical Monte Carlo (GCMC) simulations and density functional theory calculations. The results indicate that interaction between CO₂ and the framework is the main factor for determining CO₂ uptakes at low pressure, while pore size becomes the decisive factor at high pressure. The binding energy of CO₂ with functionalized linker is correlated to CO₂ uptake at 0.3 bar and 298 K on 3D-COF-1, suggesting functional groups play a key role in CO₂ capture in microporous 3D-COFs. Moreover, CO₂ selectivity over CH₄ , N₂ , and H₂ can be significantly enhanced by functionalization, where CH₂ NH₂ , COOH, SO₃ H, and E-COOH enhance CO₂ adsorption more effectively at 1 bar. Among them, SO₃ H is the most promising functional group in 3D-COFs for CO₂ separation.

Revealing the potential application of chiral covalent organic frameworks in CO2 adsorption and separation

This work uses theoretical calculations to discover the potential application of CCOFs in gas adsorption and separation, and conduct theoretical research.

Improving Covalent Organic Frameworks Fluorescence by Triethylamine Pinpoint Surgery as Selective Biomarker Sensor for Diabetes Mellitus Diagnosis

The nitrogen-containing imine or hydrazone linked covalent organic frameworks (COFs) are poorly luminescent due to the fluorescence quenching by nitrogen atoms in the linkages, even if highly luminescent units and linkers are employed. The fluorescence quenching pathway to prevent linkage-originated to mitigate the inherent limitations of the linkage is a promising method for luminescent COFs. The generation of N^- by deprotonation of the N-H unit eliminates the electron transfer from N lone pair to COF (TpPa-1) and enhances the luminescence. In this work, TpPa-1 achieved turn-on luminescence response with good sensitivity and reproducibility toward triethylamine (TEA) vapor in the process of deprotonation. The fabricated detector offers a viable approach for sensing ppm-level TEA, which can remind people to take timely measures to reduce the environmental hazards caused by TEA. The fluorescent sensor TpPa-1@LE constructed by the products of TpPa-1 and TEA can quantitatively trace biomarker methylglyoxal (MGO) for diabetes mellitus diagnosis in serum system. Furthermore, using TEA and MGO as input signals and the two fluorescence emissions G476 and Y525 as output signals, an advanced analytical device based on two Boolean logic gates with INH and AND function is constructed. This work provides a new strategy for improving the weak luminescence of COF in aqueous solution and realizes selective response to biomarker (MGO) for diabetes mellitus diagnosis.

Theoretical Investigation of the Topology of Spiroborate-Linked Ionic Covalent Organic Frameworks (ICOFs)

A novel type of ionic covalent organic framework (ICOF) with a spiroborate linkage has been recently designed and synthesized by Zhang and co-workers (Ionic Covalent Organic Frameworks with Spiroborate Linkage, Angew. Chem. Int. Ed. 2016, 55, 1737-1741). The spiroborate-linked ICOFs exhibit high Brunauer-Emmett-Teller (BET) surface areas and significant amounts of H₂ and CH₄ uptakes, combined with excellent thermal and chemical stabilities. Inspired by the novel properties of ICOFs, with the aim of gaining better understanding of the structure of such spiroborate-linked ICOFs, a series of potential 3D network configurations of ICOFs connected with tetrahedral [BO₄ ]^- nodes were proposed, assuming the [BO₄ ]^- node in spiroborate segments takes a tetrahedral configuration. These ICOFs, in terms of 2D and 3D topology through torsional energy of the [BO₄ ]^- fragment, pore-size distribution, total energy of the framework, and gas adsorption properties were compared and systematically investigated by density functional theory calculations, molecular mechanics, and well-established Grand canonical Monte Carlo simulations. The results indicate that spiroborate-linked ICOFs are likely a mixture of various topologies. Among these architectures, the five-fold interpenetrating model shows the lowest energy and reasonable gas uptakes, therefore, it is considered to be the most possible structure. More importantly, the five-fold interpenetrating model, showing high CH₄ uptakes compared with several classic porous materials, represents a promising CH₄ storage material.