Green synthesis of o-hydroxyazobenzene porous organic polymer for efficient adsorption of aromatic compounds

Preparation of GO/COFs composites by interlayer-confined strategy for the adsorption of nitro aromatic pollutants

With the continuous development of industrialization, the excessive emission of nitro aromatic with strong toxicity, high carcinogenicity and non-degradability has attracted great attention. How to efficiently remove nitro aromatic pollutants is an important research topic. In this work, graphene oxide/covalent organic frameworks (GO/COFs) composites were successfully synthesized via interlayer confinement strategy selecting GO, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTP) and 1,3,5-tri(4-aminophenyl)benzene (TPB) as raw materials. Due to high specific surface area, hierarchical porous structure and good thermal stability, GO/COFs were utilized to adsorb and remove nitro aromatic hydrocarbons in the water environment. The adsorption behavior of GO/COFs for o-nitrophenol, 1,3-dinitrobenzene and 2,4,6-trinitrophenol were further investigated. The GO/COFs composites showed the strongest adsorption capacity for 2,4,6-trinitrophenol, and the maximum adsorption capacity for 2,4,6-trinitrophenol, o-nitrophenol, and 1,3-dinitrobenzene were 438, 317, and 173 mg g-1, respectively. The experimental results indicated that the GO/COFs composites provided great adsorption capability for nitro aromatic pollutants and can be reused, rendering it an extremely potential adsorbent for organic pollutants.

Facile synthesis of hydroxylated triazine-based magnetic microporous organic network for ultrahigh adsorption of phenylurea herbicides: An experimental and density-functional theory study

Microporous organic networks (MONs) are highly porous materials that are particularly useful in analytical chemistry. However, the use of these materials is often limited by the functional groups available on their surface. Here, we described the polymerization of a sea urchin-like structure material at ambient temperature, that was functionalized with hydroxyl, carboxyl, and triazine groups and denoted as OH-COOH-MON-TEPT. A substantial proportion of OH-COOH-MON-TEPT was intricately decorated EDA-Fe3O4, creating a well-designed configuration (EDA-Fe3O4 @OH-COOH-MON-TEPT-EDC) for superior adsorption of the target analytes phenylurea herbicides (PUHs) via magnetic solid-phase extraction (MSPE). The proposed method showed remarkably low limits of detection ranging from 0.03 to 0.22 ng·L-1. Experimental investigations and theoretical analyses unveiled the adsorption mode between EDA-Fe3O4 @OH-COOH-MON-TEPT-EDC and PUHs. These findings establish a robust foundation for potential applications of EDA-Fe3O4 @OH-COOH-MON-TEPT-EDC in the analysis of various polar contaminants.

Green construction of magnetic azo porous organic polymer for highly efficient enrichment and detection of phenolic endocrine disruptors

Porous organic polymers (POPs) are prominent sorbents for effective extraction of endocrine disrupting chemicals (EDCs). However, green and sustainable construction of functional POPs is still challenging. Herein, we developed a magnetic azo POP (Mazo-POP) for the first time using hydroxy-rich natural kaempferol and low-toxic basic fuchsin as monomers through a diazo coupling reaction. The Mazo-POP exhibited excellent extraction capabilities for EDCs with a phenolic structure. Consequently, it was used as a magnetic sorbent for extracting phenolic EDCs from water and fish samples, followed by ultrahigh-performance liquid chromatography-tandem mass spectrometric detection. The Mazo-POP based analytical method afforded a good linearity of 0.06-100 ng mL-1 and 0.3-500 ng g-1 for water and fish samples respectively, with detection limits (S/N = 3) of 0.02-0.5 ng mL-1 and 0.1-1.5 ng g-1, respectively. The method recovery was from 85.2% to 109% and relative standard deviation was less 5.3%. Moreover, the effective adsorption was mainly contributed by hydrogen bond, π-π interaction, pore filling and hydrophobic interaction. This work not only provides an efficient method for sensitive determination of phenolic EDCs, but also highlights the significance of green preparation of environmentally friendly sorbents for enriching/adsorbing pollutants.

Highly Efficient Solvothermal Synthesis of Poly(1,5-diaminoanthraquinone) Nanoflowers for Energy and Environmental Applications

Poly(1,5-diaminoanthraquinone) (PDAA) has attracted more interest because of its unique molecular structure. However, the lower polymerization yield limits its practical application. Here, the solvothermal chemically oxidative polymerization of 1,5-diaminoanthraquinone (DAA) was developed, and the well-defined PDAA nanoflowers were obtained with a high yield of 72.6% within 16 h. The PDAA nanoflower-based flexible film electrodes were fabricated with expandable graphene as conductive support, delivering a capacitance of 277 F g-1 and 258 mF cm-2 at 0.5 A g-1 (1 mA cm-2) and superior cycling stability with retention of 99% after 10000 cycles. The flexible symmetric solid-state supercapacitors (SSSCs) possessed a high capacitance of 52.5 F g-1 at 0.25 A g-1 and 96.6 mF cm-2 at 1 mA cm-2 and had only a 14% capacitance loss after 10000 cycles at 0.1 V s-1 as well as excellent flexibility. Besides, the PDAA nanoflowers could be used as self-separable adsorbent for methylene blue (MB) with a capacity of 93.8 mg g-1 at pH 9.

Highly Crystalline Covalent Organic Frameworks Act as a Dual-Functional Fluorescent-Sensing Platform for Myricetin and Water, and Adsorbents for Myricetin

Selective detection of active ingredients in complex samples has always been a crucial challenge because there are many disturbing compounds, especially structural analogues that interfere with the detection. In this work, a fluorescent covalent organic framework (named COF-TD), which can be used for the selective fluorescence detection and enrichment of myricetin from complex samples, was reported for the first time. The highly crystalline COF-TD with bright blue fluorescence was formed through a solution polymerization method by the condensation reaction between 4,4',4″-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde. Due to spatial size selectivity, multisites hydrogen bonding, and π-π interaction, myricetin can quench the fluorescence of COF-TD with an inner filter effect (IFE) and static quenching mechanisms as well as can be enriched on COF-TD. Myricetin can observably eliminate the interference of other compounds and selectively quench the fluorescence of COF-TD with a limit of detection (LOD) of 0.30 μg·mL^-1. The high adsorption ability of COF-TD (Q = 124.6 mg·g^-1) to myricetin was also obtained. Finally, a sensing platform based on COF-TD for myricetin was successfully developed and applied for the detection of myricetin from vine teas. In addition, COF-TD also showed good water sensing ability and could be used effectively to detect water content in organic solvent (1-18% water in acetone, 0.5-5% water in acetonitrile, 1-4.5% water in ethyl acetate, v/v). To the best of our knowledge, this is the first report where COF-TD was used to detect water in a relatively wide concentration range. In all, this work provided dual-functional fluorescent COFs with the properties of an adsorbent, opening up new methodologies for the simple, selective, and enrichment detection method for myricetin.

Construction of hydroxyl functionalized magnetic porous organic framework for the effective detection of organic micropollutants in water, drink and cucumber samples

Organic micropollutants have been extensively detected in environmental waters, posing severe hazards to organisms and humans. Effective detection of micropollutants in environmental water and food samples is of significant importance. Herein, a novel magnetic porous organic framework (labeled as M-Qu-POF) was synthesized using natural quercetin as building units via a facile azo-coupling reaction for the first time. Featuring with good magnetism, intrinsic porosity, high surface area and hydrophilic-lipophilic (amphiphilic) structure, the M-Qu-POF displayed high adsorption capacity for phenylurea herbicides (PUHs) pollutants. The adsorption mechanism was investigated by theory calculation, confirming that the hydrogen bonds interaction, π-π interactions and electrostatic interactions play an important role in the adsorption. With the M-Qu-POF as adsorbent, a magnetic solid phase extraction-high performance liquid chromatography method was first established for simultaneous enrichment and detection of six PUHs in environmental water, tea drink and cucumber samples. Under the optimized experimental conditions, good linear range, low detection limits and high enrichment factors were obtained. The method was successfully applied for determination of PUHs in environmental water, tea drink and cucumber samples with satisfactory recoveries (80.0-118%). The result demonstrates that the M-Qu-POF material has a good application prospect in the detection of other organic micropollutants.

Porous Organic Polymer Synthesized by Green Diazo-Coupling Reaction for Adsorptive Removal of Methylene Blue

A porous organic polymer (marked as DT-POP), which contains abundant free phenolic hydroxyl groups, is synthesized by the well-known green azo-coupling reaction in water, characterized, and utilized as an effective adsorbent for the elimination of methylene blue (MB) from water solutions. The presence of permanent mesopores, abundant active functional groups, and π-electron enrichment ascribed to phenyl rings make DT-POP an efficient adsorbent for MB due to strong hydrogen bonding, π-π, and electrostatic interactions with the cationic dye MB. DT-POP with high stability and high adsorption capacity can be reused many times and thus shows high applicability in pollutant disposal.

[Synthesis and application progress of covalent organic polymers in sample preparation for food safety analysis]

Food safety is closely related to human health and life. Contaminated foods may result in illness or poisoning. For example, perfluorinated compounds can concentrate in the human body, or they can be transferred to the baby during breastfeeding, thus leading to serious health risks. Phthalate esters may cause damage to the liver, lungs, and kidneys. Therefore, food safety has become a hot topic at a global level. Poisonous and harmful substances in foods are derived from the environment, planting or breeding, food contacting materials, and food processing, or due to unsuitable storage conditions. Residues of pesticides and veterinary drugs, organic pollutants, additives, heavy metals, and biotoxins often hamper food safety, causing diseases or even death. The diversity of available food species, complexity of the sample matrix, and lack of information about the source of pollutants render the direct determination of food contaminants difficult. Pretreatment is vital for the accurate analysis of trace toxins in foods. Optimal pretreatment can not only improve the extract efficiency and determination sensitivity, but also prevent instrument contamination. Pretreatment techniques have played an important role in trace determination for complex matrices. Pretreatment methods can be classified as solvent-based and adsorption-based methods. Adsorption-based techniques such as solid-phase extraction, magnetic solid-phase extraction, and solid-phase microextraction are simple and efficient, and hence, are widely used. In these pretreatment techniques, adsorbents play a key role in the extraction effect. In the last few years, metal organic frameworks, metal oxide materials, carbon nanotubes, graphene, and magnetic nanoparticles, as well as a combination of these materials, have been used as adsorbents. These materials are porous and have a large surface area; they are used to enrich trace targets and eliminate interferents. Covalent organic polymers (COPs) are a class of organic porous materials constructed from organic monomers via covalent bonding. Given their excellent characteristics such as light density, good stability, high surface area, structural controllability, and ease of modification, COPs are potential adsorbents. COPs are often synthesized by solvent thermal methods. However, these methods are time-consuming and require toxic solvents and harsh reaction conditions. As alternatives, room-temperature methods, mechanical chemical methods, microwave-assisted methods, and UV-assisted methods have been developed. This has facilitated the synthesis of a wide range of COPs. In this article, the recent applications of COPs in sample pretreatment for food safety analysis are reviewed. COPs can be used in solid-phase extraction by simple packing into columns, polymerization, or chemical bonding in the capillary. Magnetic compounds have been prepared by one-pot synthesis, in situ growth, in situ reduction, or coprecipitation methods and used in magnetic solid-phase extraction. Coatings of solid-phase microextraction fibers are fabricated by physical methods, chemical bonding, sol-gel methods, or in situ growth. Toxic and harmful substances in foods and foodstuffs are efficiently extracted by exploiting the high adsorbent capacities and specificity of COPs. Future development prospects and challenges in sample pretreatment are also discussed herein. There is increased focus on the development of simple, efficient, and environment-friendly methods to synthesize COPs with specific functions; further, high-throughput, sensitive analytical methods may be established. In the future, more specific COPs will be prepared in a cost-effective manner for widespread use in sample pretreatment.

Analytical methods to analyze pesticides and herbicides

This paper reviews studies published in 2019, in the area of analytical techniques for determination of pesticides and herbicides. It should be noted that some of the reports summarized in this review are not directly related to but could potentially be used for water environment studies. Based on different methods, the literatures are organized into six sections, namely extraction methods, electrochemical techniques, spectrophotometric techniques, chemiluminescence and fluorescence methods, chromatographic and mass spectrometric techniques, and biochemical assays. PRACTITIONER POINTS: Totally 141 research articles have been summarized. The review is divided into six parts. Chromatographic and mass spectrometric techniques are the most widely used methods.

Combination of magnetic solid-phase extraction and HPLC-UV for simultaneous determination of four phthalate esters in plastic bottled juice

A magnetic o-hydroxyazobenzene (M-HAzo) porous organic polymer was facilely prepared by a green azo coupling reaction in aqueous solution. The prepared M-HAzo was applied as a new adsorbent for the first time to pre-concentrate phthalate esters (PAEs) from plastic bottled juice, followed by their determination with high performance liquid chromatography-ultraviolet detection. The effects of various parameters, i.e., the mass ratio of the Fe₃O₄@SiO₂ to HAzo, extraction time, ionic strength, pH of the sample, desorption conditions were optimized. Under the optimized conditions, the M-HAzo based method exhibited good performance in terms of linear range (0.3-50.0 μg L^-1), detection limit (0.08-0.50 μg L^-1), accuracy (recovery of 78.0-115.0%) and repeatability (relative standard deviation of 2.9-7.8%). This work provides a sensitive method for analysis of PAEs at trace levels in drinks, which is featured with high sensitivity, simple operation and environmentally-friendly merit and will have a promising potential in analysis of other organic pollutants.