Facile synthesis of a novel magnetic covalent organic frameworks for extraction and determination of five fungicides in Chinese herbal medicines

A novel magnetic covalent organic framework was synthesized via a one-step coating approach with solvothermal reaction employing 2,4,6-tris(4-aminophen-yl)-1,3,5-triazine and 2,4,6-triformylphloroglucinol as two building blocks by covalent bonding. The prepared magnetic covalent organic frameworks were properly characterized by different techniques and employed as adsorbents of magnetic solid-phase extraction. An analytical method was developed for the simultaneous determination of five fungicides in two Chinese herbal medicine samples via magnetic solid-phase extraction coupled to ultra high performance liquid chromatography with tandem mass spectrometry analysis. Under optimized magnetic solid-phase extraction conditions, the method exhibited satisfactory recoveries (74.0−109.6%) with relative standard deviations of 0.4−4.6%, low limits of detection (0.003−0.015 μg/kg), and good linearity (R² > 0.9960). Compared with the traditional extraction method, the proposed method required a lower amount of adsorbent (3 mg) and extraction time (5 min). The adsorbent also had favorable reusability (not less than eight times). Therefore, the magnetic covalent organic frameworks could be a promising adsorbent for the extraction and quantitation of fungicides in Chinese herbal medicines.     

One-pot synthesis of magnetic sulfonated covalent organic polymer for extraction of protoberberine alkaloids in herbs and human plasma

A novel magnetic sulfonated covalent organic polymer was prepared for magnetic solid-phase extraction of protoberberine alkaloids. The magnetic sulfonated covalent organic polymer was rapidly synthesized under mild conditions. The physicochemical properties of the prepared materials were characterized by Fourier-transform infrared spectrometry, transmission electron microscopy, and X-ray photoelectron spectroscopy. Several extraction parameters were systematically investigated, including desorption time, pH of sample solution, acetonitrile content, acetic acid content in the eluent, extraction time, and sample volume. By coupling magnetic solid-phase extraction and high-performance liquid chromatography, an efficient and sensitive method for the extraction and determination of protoberberine alkaloids in complex samples was developed. The proposed method showed great linearity (r > 0.9989), low limits of detection (0.2–0.3 ng/ml), and high precision (relative standard deviations ≤ 5.74%). The proposed method was further applied to the analysis of protoberberine alkaloids in Cortex phellodendri and human plasma samples. The recoveries were 91.50%–110.31% with relative standard deviations less than 6.63% in Cortex phellodendri and 96.12%–111.20% with relative standard deviations lower than 5.56% in plasma samples.     

亚胺类共价有机骨架材料在样品前处理中的应用

亚胺类共价有机骨架(I-COFs)是有机单体根据席夫碱(Schiff-base)反应原理缩合形成的一类新型多孔晶体有机材料.I-COFs具有骨架密度低、比表面积大、孔隙率高、单体种类丰富、孔径尺寸可控、结构可功能化、合成方法多样和物化稳定性好等优点.近年来,I-COFs已成为材料科学领域的研究前沿,并广泛用于气体吸附、...     

二维Ni-Salphen基共价有机骨架的制备及电容性能

利用2,3,6,7,10,11-六氨基三苯六盐酸盐（HATP）和4,6-二羟基-5-甲基间苯二甲醛（DMDB）为构筑基元,构筑了二维Ni-Salphen基共价有机骨架（COFs）电极材料（Ni-Salphen-COF）。通过一系列方法对Ni-Salphen-COF的结构、形貌和电化学性能进行了表征和测试。三电极系统测试结果表明,Ni-Salphen-COF具有优异的电化学性能,在1 A·g^-1时,比电容达到531 F·g^-1,并显示良好的循环稳定性（10 000次循环后电容保持率为89%）。同时,二电极系统测试结果显示,在1 A·g^-1时,Ni-Salphen-COF//AC （AC为活性炭）比电容达176 F·g^-1;在功率密度为900 W·kg^-1时,最大能量密度为55 Wh·kg^-1。良好的性能可能归因于Ni-Salphen结构提高了电极材料的电导率、氧化还原活性和电荷转移能力。     

Primary amide-functionalized cyclotricatechylene covalent organic frameworks membrane for efficient enrichment of melamine and its derivatives in migration solution of food contact materials

A highly chemically stable primary amide-functionalized cyclotricatechylene covalent organic framework was synthesized by an irreversible reaction and a post-synthetic modification. It possessed a rod-like morphology and exhibited strong solvent stability owing to the polyether bonds. The material showed good adsorption performance for melamine and its derivatives and adsorption mechanism was investigated by molecular simulations. The adsorbent was coated on the nylon-66 membrane to prepare the enrichment membrane. Under optimized conditions, an in-syringe membrane-based extraction method, combined with ultra-high performance liquid chromatography-tandem mass spectrometry was developed for the analysis of melamine and six melamine derivatives in the migration solution. A good linearity was obtained with correlation coefficients ranging from 0.9924 to 0.9995. The limits of detection were 1–200 ng/L and the limits of quantification were 3–500 ng/L. This method was successfully applied to the migration solution of sushi bamboo rolling mats with spiked recoveries of 73.2%–115% and relative standard deviations of 0.9%–9.9%. This work shows a practical and perspective approach for the efficient enrichment of food contact material hazards.     

Cobalt-containing covalent organic frameworks for visible light-driven hydrogen evolution

Covalent organic frameworks(COFs) have recently emerged as a new class of photocatalysts.However,integrated design is crucial to maximizing the performance of COF-incorporating photocatalytic systems.Herein,we compare two strategies of installing earth-abundant metal-based catalytic centers into the matrice of a 2 D COF named NUS-55.Compared to NUS-55(Co)prepared from the post-synthetic metalation of coordination sites within the COF,the molecular co-catalyst impregnated NUS-55/[Co(bpy)3]Cl2 achieves a seven-fold improvement in visible light-driven H2 evolution rate to 2,480 μmol g^-1h^-1,with an apparent quantum efficiency(AQE) of 1.55% at 450 nm.Our results show that the rational design of molecular anchoring sites in COFs for the introduction of catalytic metal sites can be a viable strategy for the development of highly efficient photocatalysts with enhanced stability and photocatalytic activities.     

Facile synthesis of spherical covalent organic frameworks for enrichment and quantification of aryl organophosphate esters in mouse serum and tissues

Here, an imine-linked-based spherical covalent organic framework (COF) was prepared at room temperature. The as-synthesized spherical COF served as an adsorbent in dispersive solid-phase extraction (dSPE), by its virtue of great surface area (1542.68 m²/g), regular distribution of pore size (2.95 nm), and excellent stability. Therefore, a simple and high-efficiency dispersive solid phase extraction method based on a spherical COF coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established to determine aryl organophosphate esters in biological samples. This approach displayed favorable linearity in the range of 10.0–1000.0 ng/L (r > 0.9989), a high signal enhancement factor (58.8–181.8 folds) with low limits of detection (0.3–3.3 ng/L). Moreover, it could effectively eliminate complex matrix interference to accurately extract seven aryl organophosphate esters from mouse serum and tissue samples with spiked recoveries of 82.0%–117.4%. The as-synthesized spherical COF has been successfully applied in sample preparation. The dSPE-HPLC-MS/MS method based on a spherical COF has potential application to study the pollutants' metabolism in vivo.     

Recent advances in metal‐organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal‐organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF‐ or COF‐based solid‐phase extraction (SPE), solid‐phase microextraction (SPME), gas chromatography (GC), high‐performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.     

Stable hydrazone-linked chiral covalent organic frameworks: Synthesis,modification, and chiral signal inversion from monomers

The designed synthesis of chiral covalent organic frameworks(COFs) featuring intriguing properties is fairly scant and remains a daunting synthetic challenge.Here we develop a de novo synthesis of an enantiomeric pair of 2 D hydroxyl-functionalized hydrazone-linked chiral COFs,(S)-and(R)-HthBta-OH COFs,using enantiopure 2,5-bis(2-hydroxypropoxy)terephthalohydrazide(Hth) as monomers.The fo rmation process of hydroxyl-functionalized chiral COFs was monitored using rigorous time-dependent PXRD,vibrational circular dichroism(VCD),and electronic circular dichroism(ECD) studies.Remarkably,VCD spectra indicated a unique chiral signal inversion from the positive Cotton effect of(S)-Hth monomer to the negative Cotton effect of(S)-HthBta-OH COF,which has never been reported in chiral COFs.Moreover,two unprecedented carboxyl-functionalized chiral COFs,(S)-and(R)-HthBta-COOH,were constructed by a post-synthetic modification of the corresponding hydroxyl chiral COFs with succinic anhydride.Notably,carboxyl-functionalized COFs retained homochirality and crystallinity without linker racemization and structural collapse after the chemical modification due to the chemically robust nature of pristine hydrazone-linked chiral COFs.     

Synthesis,characterization, and hydrazine sensing property of two covalent organic frameworks

Sensitive and efficient detection of hydrazine is of great significance because hydrazine is a highly toxic organic molecule, which can pose great threats to human health. Herein, two covalent organic frameworks (COFs) modified with ester groups in the pores, TAPB-DHE and TAPT-DHE, have been successfully synthesized via esterification reaction. Both of the two COFs have good crystallinity, thermal stability, and fluorescence properties. TAPB-DHE can be used as a turn-on fluorescence sensor for the sensitive detection of trace hydrazine in aqueous solution with a detection limit of 0.40 μM and a wide linear range of 0–100 μM due to the fluorescence enhancement of TAPB-DHE caused by the chemical reaction between hydrazine and TAPB-DHE, in which the ester group of the COF is converted into hydroxyl group, leading to the restriction of the intramolecular charge transfer (ICT) effect. This work provides a reference for the design of COFs with hydrazine recognition function and a helpful expansion for the practical application of COFs.     

Covalent organic frameworks for applications in lithium batteries

With the stone energy increasingly dried up and the environment polluted severely, developing renewable clean energy is already in extreme urgency. Exploiting new energy storage and transformation systems has progressively become the focal point in the energy research field. Covalent organic frameworks (COFs) have attracted extensive attention as a new kind of crosslinked polymers owing to the high crystallinity, excellent porosity, and favorable stability. The last decade has witnessed the great progress in crystalline COFs for the application in various arenas. The tailor-made functional skeleton together with well-defined periodical alignment has endowed COFs with enormous potential in lithium batteries. In this review, we initially illustrated the design principle of COFs for the application in lithium batteries. Furthermore, we made a comprehensive summary of the fast-developing COFs field in terms of lithium batteries, including lithium ion and lithium sulfur batteries. Finally, we discussed the remaining challenges and perspectives in this area and also proposed several possible future directions of development for lithium batteries. It is expected that this short review would contribute to the development of COFs materials in energy-related applications.     

共价有机框架材料磁固相萃取-高效液相色谱法分析环境水体中对羟基苯甲酸酯

建立了一种基于共价有机框架材料的磁固相萃取-高效液相色谱方法,用于环境水样中对羟基苯甲酸酯的快速灵敏分析。首先以Fe₃O₄纳米粒子为磁核,通过1,3,5-苯三甲醛(Tb)和联苯胺(Bd)在室温下的席夫碱反应合成了磁性共价有机框架材料——Fe₃O₄@TbBd,通过扫描电镜、热重分析、X射线衍射和振动样品磁强计等表征手段证明了该磁性共价有机框架材料具有良好的热稳定性和化学稳定性,且磁响应强度较大,是用于磁固相萃取的理想材料。随后系统研究了影响萃取效率的因素,包括吸附剂用量、萃取时间、pH、解吸溶剂、解吸时间和解吸次数,建立了基于Fe₃O₄@TbBd的磁固相萃取-高效液相色谱测定环境水样中4种对羟基苯甲酸酯的方法。方法的线性范围良好,4种目标物的检出限和定量限范围分别为0.2~0.4 μg/L和0.7~1.4 μg/L,加标回收率为86.1%~110.8%,日内和日间精密度的相对标准偏差(RSD)分别低于5.5%和4.9%。最后将该方法应用于东湖水、长江水和生活废水中对羟基苯甲酸酯的测定,不同加标水平下对羟基苯甲酸酯的回收率在80.7%~117.5%之间,RSD在0.2%~8.8%之间。该方法操作简单,萃取时间短,灵敏度较高且对环境友好,在环境水样中对羟基苯甲酸酯的检测方面有良好的应用潜力。     

High-rate charge-carrier transport in porphyrin covalent organic frameworks: switching from hole to electron to ambipolar conduction

Well conducted: a two-dimensional porphyrin covalent organic framework is described. Owing to the eclipsed stacking alignment, the framework is conductive and allows high-rate carrier transport through the porphyrin columns. The central metal in the porphyrin rings changes the conducting nature of the material from hole to electron, and to ambipolar conduction. It also drives the high on-off ratio photoconductivity of the framework.     

共价有机骨架材料在样品前处理中的研究进展

共价有机骨架（COFs）是由有机单体通过共价键连接形成的二维或三维晶体多孔结构。作为一种新兴的晶体多孔材料,COFs已经在气体储存、催化、传感、药物输送等各个领域广泛应用。近年来,COFs材料由于密度低、表面积大、结构可控等优点,在分析化学方面显示出巨大的潜力。该文综述了多孔COFs及其复合材料在样品前处理中的研究应用,包括分散固相萃取、固相微萃取和磁性固相萃取等。     

量子化学计算解析手性共价有机框架材料6色谱固定相的手性拆分机理

为探究手性共价有机框架材料6(Chiral Covalent Organic Frameworks 6, CCOF6)色谱固定相的手性拆分机理,首先运用ORCA程序对CCOF6及4对手性对映体进行结构优化,然后使用AutoDock程序对CCOF6及各对映体分子进行分子对接,获得CCOF6与对映体相互作用的初始构型;采用ORCA程序(B3LYP泛函,带DFT-D3校正,轨道基组为def2-TZVP, def2/J作为RI-J的辅助基组,RIJCOSX用来加速计算)对初始构型进行能量计算,以最终确定CCOF6与对映体的相互作用构型,并获得相应的结合自由能和结合自由能差;使用Multiwfn程序对ORCA结果进行独立梯度模型分析,并应用视觉分子动力学程序可视化展示CCOF6与对映体的弱相互作用。结果表明:(1)在计算结合自由能方面,考虑了溶剂效应的ORCA计算方法比不考虑溶剂效应的ORCA以及AutoDock计算方法更为精确;(2)CCOF6色谱固定相与对映体之间的结合自由能差绝对值越大,对映体的选择性因子也越大,然而对映体的分离度不一定会越大;(3)除S-1-苯基-1-丙醇是以羟基和CCO...     

Fabrication of magnetic zinc adeninate metal–organic frameworks for the extraction of benzodiazepines from urine and wastewater

In this study, an alternative method for synthesizing magnetic cobalt adeninate metal–organic frameworks was developed, and the synthesized materials were examined for their potential application for separating and enriching benzodiazepines from complex samples. Benzodiazepines, widely used as hypnotics, muscle relaxants, sedatives, and anxiolytics, are a class of drugs that require accurate detection and monitoring. Results showed that Fe₃O₄ nanoparticles could be well anchored onto the external surface of cobalt adeninate metal–organic frameworks by using amino‐silane as a linkage. Their adsorption of benzodiazepines was mainly promoted by intermolecular hydrogen binding, π–π interactions and electrostatic attraction. Their potential application was evaluated by extraction of benzodiazepines in urine and wastewater samples prior to liquid chromatography with mass spectrometry. Under optimum conditions, the calibration curves were linear with a correlation coefficient of ≥0.9928 in the concentration range of 10–5000 ng/L for lorazepam and 5–5000 ng/L for estazolam, chlordiazepoxide, alprazolam, midazolam and triazolam. The limits of detection were in the range of 0.71–2.49 ng/L. The percent of extraction recoveries were 80.2–94.5% for urine and 84.1–94.4% for wastewater, respectively. Results suggested that magnetic cobalt adeninate metal–organic frameworks could potentially be a promising material for enriching benzodiazepines from urine and wastewater with high accuracy and precision.     

Fabrication of highly crystalline covalent organic framework for solid-phase extraction of three dyes from food and water samples

Herein, a covalent organic framework, which was fabricated at room temperature by using 1,3,5-tris(p-formylphenyl) benzene and 1,3,5-tris(4-aminophenyl)benzene as building blocks, was employed as an adsorbent for solid-phase extraction of dyes including congo red, methyl blue and direct red 80 for the first time. The prepared covalent organic framework was properly characterized by different techniques and the results revealed that it had a uniform spherical structure, high crystallinity, satisfactory surface area, and good thermal stability. Moreover, the adsorption performance of the material was explored by using static and dynamic adsorption experiments and the results indicated that the material showed good adsorption capacities for three dyes with adsorption capacities in the range of 55.25–284.10 mg/g and the adsorption equilibrium can be achieved in 15 min. Further, to achieve the best adsorption effects of the material, the influence parameters such as pH, ionic strength, type of desorption solvent, and the material dosage in the solid-phase extraction column, were optimized in turn. Finally, under optimal conditions, the solid-phase extraction coupled with HPLC was applied to the analysis of dyes in food and water samples. The recoveries of dyes in actual samples were satisfactory, revealing the unique applicability of the material in the sample pretreatment field.     

Covalent organic frameworks as advanced materials in the application of chemical detection

With the development of industrialization, chemical detection plays a vital role in many fields. As a new type of porous material, covalent organic frameworks (COF's) possess the characteristics of huge specific surface area, low density, great stability, and adjustable pore size. These characteristics make it a great prospect for chemical detection. In the article, we mainly show how to design several analytic platforms to achieve precise target detection by utilizing the special properties of COF's, put forward the relevant mechanisms of successful detections, and analyze the related parameters of analyte detection performance. Finally, the current challenges of chemical detection based on COF's are presented, and we also prospect the future research directions.