Cascade Knoevenagel condensation-chemoselective transfer hydrogenation catalyzed by Pd nanoparticles stabilized on amine-functionalized aromatic porous polymer

Synthesis of cyano and ionic dual-functional hypercrosslinked porous polymer for effective adsorption and detection of endocrine disrupting chemicals in milk matrix

Endocrine disrupting chemicals (EDCs) can interfere with the normal function of endocrine system, posing serious risk to human health. The monitoring of EDCs in foods is of great importance to ensure food security. Herein, a cyano and ionic dual-functionalized hypercrosslinked porous polymer (CN-iHCP) was designed and prepared for the first time through hyper-crosslink of 1-(4-cyanophenyl)imidazole and 1,4-bis(chloromethyl)benzene. The adsorption mechanism mainly involves electrostatic interaction, hydrogen bonding and π-π stacking interaction. A sensitive analytical method for simultaneous detection of the four phenolic EDCs was established by coupled CN-iHCP based solid-phase extraction with high performance liquid chromatography. Under optimal conditions, the target EDCs exhibited good linearity with coefficient r > 0.993 and high enrichment factors of 164-243. The detection limits (S/N = 3) of EDCs were 0.20-0.50 ng mL-1 for milk sample. The extraction recoveries for the spiked milk samples were in the range of 85.5%- 116.0%. This work not only highlights the CN-iHCP as a promising adsorbent to efficiently enrich EDCs and other pollutants, but also provides a new strategy for the functionalization of HCP for wide applications.

Preparation of a magnetic phosphazene-based hyper crosslinked polymer for the fast and efficient extraction of chlorophenols from water and peach juice

Two magnetic phosphazene-based hyper crosslinked polymers (M-HCP-OP-TMC and M-HCP-OP-TCL) were newly synthesized by the reaction of Friedel-Crafts acylation, and the M-HCP-OP-TMC showed an excellent extraction capability and rapid adsorption kinetics for chlorophenols as an adsorbent. Then, an efficient analytical method was built for the preconcentration and quantification of chlorophenols from water and peach juice samples by combining M-HCP-OP-TMC based magnetic solid-phase extraction (MSPE) with HPLC-UV detection. The linear response range for the chlorophenols by the method was 0.21-100.0 ng mL-1 for water sample, and 0.36-100.0 ng mL-1 for peach juice sample. The detection limits (S/N = 3) of the proposed method for the analytes were 0.07- 0.25 ng mL-1 and 0.12-0.45 ng mL-1 for water and peach juice samples, respectively. The method recoveries for the spiked samples were in the range of 93.1%-117.1%, and the relative standard deviations were less than 10%. The adsorption of the chlorophenols with the M-HCP-OP-TMC was mainly contributed by π-π stacking and hydrophobic interactions. The results indicate that the method was sensitive and accurate enough for the determination of the chlorophenols from real samples.

Synthesis of amine-functionalized magnetic porous organic polymers for effective extraction of phenolic endocrine disrupting chemicals

Amine-functionalized porous organic polymers (EDA-POP-PC and EDA-POP-BT) were prepared by post-modification of POP-PC and POP-BT with ethylenediamine (EDA) for the first time. The POP-PC and POP-BT were obtained through Friedel-Crafts acylation reaction of potassium tetraphenylborate with p-phthaloyl chloride (PC) and 1,3,5-benzenetricarbonyl trichloride (BT), respectively. The EDA-POPs exhibited superior adsorption capacity for phenolic endocrine disrupting chemicals (EDCs). After magnetically functionalization, the obtained M-EDA-POP-PC was employed as a magnetic adsorbent for enrichment of phenolic EDCs from real samples prior to high performance liquid chromatography-ultraviolet detection. The current strategy showed low detection limits (S/N = 3) of 0.02-0.07, 0.04-0.08 and 0.04-0.10 ng mL-1 for river water, white peach juice and lychee juice, respectively. The method recoveries were 81.7%-115% with relative standard deviations below 8.6%. The proposed strategy showed good practicality for sensitive determination of phenolic EDCs in real samples.

Nitrate pollution and its solutions with special emphasis on electrochemical reduction removal

Nitrate pollution has become a serious environmental concern all over the world including in China due to the mismanagement of water resources and human activities. Agricultural runoff and industrial and nuclear waste are among the major sources of nitrate pollution. Consuming nitrate-rich water can cause many chronic diseases including digestive problems, which can lead to many types of cancer and other serious health issues. Denitrification is the natural process for nitrate reduction under aerobic conditions, but it cannot handle an excess of nitrate, so several methods have been adopted for nitrate removal, i.e., biological, chemical, physicochemical, and electrochemical reduction removal. Among all, electrochemical reduction removal is a cost-effective and environmental-friendly process. To obtain the maximal elimination efficiency ideal conditions of current intensity, pH, plate distance, initial nitrate concentration, and type of electrolyte solution should be studied for effective nitrate removal. Electrochemical reduction removal of nitrate involves the transfer of electrons and hydrogenation. Besides an efficient nitrate removal process, electrochemical reduction removal has some drawbacks like sludge formation, low selectivity for nitrogen, and production of brine that limit its long-term implementation. This review focused on nitrate pollution, previous nitrate removal strategies, and essential principles for understanding the mechanism of electrochemical reduction removal and controlling the products of the reaction.

Sensitive determination of auxins in environmental water and peach beverage by hyper crosslinked polymer-based solid-phase extraction with high performance liquid chromatography-fluorescence detection

As plant regulators, auxins can promote plant growth. However, they have toxicity and may cause harm to humans. Due to their low concentrations in food sample matrices, the enrichment and analysis of trace auxins in food samples is a challenging work. In this work, a series of hyper crosslinked polymers (HCPs) were synthesized by Friedel-Crafts acylation to extract four auxins (indole-3-acetic acid, indole-3-propionic acid, indole-3-butyric acid and 1-naphthylacetic acid). Among these HCPs, the QP-TC-HCP, synthesized from p-quaterphenyl (QP) and terephthaloyl chloride (TC), showed the best adsorption performance for the auxins. It was then applied as the adsorbent for the solid-phase extraction of the auxins from environmental water and peach beverage samples, followed by high performance liquid chromatography-fluorescence detection. Under the optimized conditions, the limits of detection were 3.0-12.0 pg mL^-1 for environmental water and 18.0-36.0 pg mL^-1 for peach beverage sample. The method recoveries of the auxins for the spiked samples were in the range of 85.0-110.0%. The established method provided an alternative approach for the determination of auxins in food samples. In addition, different types of organic compounds were tested for the extraction by the QP-TC-HCP to assess its application potential and adsorption mechanism. It was concluded that the QP-TC-HCP had better extraction performance for the compounds with certain hydrophilicity and more hydrogen bonding sites.

Base-Free Synthesis and Photophysical Properties of New Schiff Bases Containing Indole Moiety

Schiff bases represent an essential class in organic chemistry with antitumor, antiviral, antifungal, and antibacterial activities. The synthesis of Schiff bases requires the presence of an organic base as a catalyst such as piperidine. Base-free synthesis of organic compounds using a heterogeneous catalyst has recently attracted more interest due to the facile procedure, high yield, and reusability of the used catalyst. Herein, we present a comparative study to synthesize new Schiff bases containing indole moieties using piperidine as an organic base catalyst and Au@TiO₂ as a heterogeneous catalyst. In both methods, the products were isolated in high yields and fully characterized using different spectral analysis techniques. The catalyst was reusable four times, and the activity was slightly decreased. The presence of Au increases the number of acidic sites of TiO₂, resulting in C=O polarization. Yields of the prepared Schiff bases in the presence of Au@TiO₂ and piperidine were comparable. However, Au@TiO₂ is an easily separable and recyclable catalyst, which would facilitate the synthesis of organic compounds without applying any hazardous materials. Furthermore, the luminescence behavior of the synthesized Schiff bases exhibited spectral shape dependence on the substituent group. Interestingly, the compounds also displayed deep-blue fluorescence with Commission Internationale de l'Éclairage (CIE) coordinates of y < 0.1. Thus, these materials may contribute to decreasing the energy consumption of the emitting devices.

Yolk-shell smart Pickering nanoreactors for base-free one-pot cascade Knoevenagel-Hydrogenation with high catalytic efficiency in water

In present work, Au@Pd nanoparticles, catalytic active centers, were first implanted in amphiphilic hollow vinyl-pyridyl groups-doped periodic mesoporous organosilica (PMO) shells, and we got yolk–shell smart Pickering Au@Pd@Py-PMO nanoreactors. Two...

Fabrication of carbonyl-functional hypercrosslinked polymers as solid-phase extraction sorbent for enrichment of chlorophenols from water, honey and beverage samples

Three carbonyl-functional novel hypercrosslinked polymers (HCP-TPS, HCP-TPA, and HCP-TPP) were successfully fabricated through an one-step Friedel-Crafts acylation reaction by copolymerizing paraphthaloyl chloride with triphenylsilane, triphenylamine, and triphenylphosphine, respectively. The resultant HCPs contained plenty of carbonyl-functional groups. Among the series of such HCPs, HCP-TPS displayed the best adsorption capability to chlorophenols (CPs), and thus it was employed as solid-phase extraction (SPE) adsorbent for enrichment of chlorophenols from water, honey, and white peach beverage prior to determination by high-performance liquid chromatography. Under the optimal conditions, the detection limits of the method (S/N = 3) were 0.15-0.3 ng mL^-1 for tap water and leak water, 2.5-6.0 ng g^-1 for honey sample and 0.4-0.6 ng mL^-1 for white peach beverage sample. The recoveries of CPs in the spiked water, honey samples, and white peach beverage were in the range of 89.0-108.4%, 81.4-118.2%, and 85.0-113.5%, respectively. This work provides a new strategy for constructing functionalized HCPs as efficient SPE adsorbents. In this work, three novel hypercrosslinked polymers (HCPs) were synthesized by the Friedel-Crafts alkylation reaction (paraphthaloyl chloride as the alkylating agent, triphenylsilane, triphenylamine, and triphenylphosphine as the aromatic units). Then, HCP-TPS was applied to soild-phase extraction sorbent for enrichment CPs from water, honey, and white peach beverage samples.

Evaluation of an Ionic Porous Organic Polymer for Water Remediation

The targeted synthesis of a novel ionic porous organic polymer (iPOP) was reported. The compound (denoted as QUST-iPOP-1) was built up through a quaternization reaction of tris(4-imidazolylphenyl)amine and cyanuric chloride, and then benzyl bromide was added to complete the quaternization of the total imidazolyl units. It featured a special exchangeable Cl^-/Br^--rich structure with high permanent porosity and wide pore size distribution, enabling it to rapidly and effectively remove environmentally toxic oxo-anions including Cr₂O₇^2-, MnO₄^-, and ReO₄^- and anionic organic dyes with different sizes including methyl blue, Congo red, and methyl orange from water. Notably, QUST-iPOP-1 showed ultra-high capacity values for radioactive TcO₄^- surrogate anions (MnO₄^- and ReO₄^-), Cr₂O₇^2-, methyl blue, and Congo red, and these were comparable to some reported compounds of exhaustive research. Furthermore, the relative removal rate was high even when other concurrent anions existed.

Palladium and Copper: Advantageous Nanocatalysts for Multi-Step Transformations

Metal nanoparticles have been deeply studied in the last few decades due to their attractive physical and chemical properties, finding a wide range of applications in several fields. Among them, well-defined nano-structures can combine the main advantages of heterogeneous and homogeneous catalysts. Especially, catalyzed multi-step processes for the production of added-value chemicals represent straightforward synthetic methodologies, including tandem and sequential reactions that avoid the purification of intermediate compounds. In particular, palladium- and copper-based nanocatalysts are often applied, becoming a current strategy in the sustainable synthesis of fine chemicals. The rational tailoring of nanosized materials involving both those immobilized on solid supports and liquid phases and their applications in organic synthesis are herein reviewed.

Postfunctionalization of Porous Organic Polymers Based on Friedel-Crafts Acylation for CO2 and Hg2+ Capture

Melamine-based porous organic polymers (POPs) are promising for gas uptake and water treatment because of their unique and tunable porosity, high nitrogen (N) content, and high Brunauer-Emmett-Teller (BET) surface area (S_BET). However, it is difficult to construct ketone-based POPs by the Friedel-Crafts acylation reaction. Herein, the ketone-based POPs were postfunctionalized with melamine (MA) by the Schiff-based reaction and the rigid triazine rings of MA were embedded in the polymer chains as rigid cross-linkers, resulting in the polymers with high S_BET (555 m²·g^-1) and total pore volume (0.72 cm³·g^-1). Moreover, plentiful imine, amino, and triazine functionalities were inserted in the polymers, providing the polymers with high N content of 41.83 wt %. The resulting polymers were promising for CO₂ capture (145 mg·g^-1; 273 K, 1.0 bar) and Hg²⁺ removal (372 mg·g^-1). This study offers a universal strategy to construct melamine-based POPs from various ketone-functionalized HCPs via a simple postfunctionalization.