Palladium Supported on an Amphiphilic Triazine-Urea-Functionalized Porous Organic Polymer as a Highly Efficient Electrocatalyst for Electrochemical Sensing of Rutin in Human Plasma

Urea-rich porous organic polymer as a hydrogen bond catalyst for Knoevenagel condensation reaction and synthesis of 2,3-dihydroquinazolin-4(1H)-ones

In this research, a new urea-rich porous organic polymer (urea-rich POP) as a hydrogen bond catalyst was synthesized via a solvothermal method. The physiochemical properties of the synthesized urea-rich POP were investigated by using different analyses like Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), energy-dispersive X-ray spectroscopy (EDS), elemental mapping analysis, X-ray diffraction analysis (XRD) and Brunauer-Emmett-Teller (BET) techniques. The preparation of urea-rich POP provides an efficacious platform for designing unique hydrogen bond catalytic systems. Accordingly, urea-rich POP, due to the existence of several urea moieties as hydrogen bond sites, has excellent performance as a catalyst for the Knoevenagel condensation reaction and multi-component synthesis of 2,3-dihydroquinazolin-4(1H)-ones.

Efficient Reduction in Methylene Blue Using Palladium Nanoparticles Supported by Melamine-Based Polymer

In this work, palladium nanoparticles, supported by polyaminals (Pd@PAN-NA), were synthesized via a reverse double solvent approach and used as a nano catalyst. The thermogravimetric and the elemental analysis revealed that the catalyst had good dispersity and improved thermal stability. The catalytic activity of the prepared Pd@PAN-NA catalyst was studied for a methylene blue chemical reaction in the presence of NaBH4 as a reducing agent. The effect of the catalyst dose, pH, and dye initial concentration were examined to optimize the chemical reduction conditions. The prepared catalyst Pd@PAN-NA removed 99.8% of methylene blue organic dye, indicating its potential effect for treating waste and contaminated water.

Novel N-riched covalent organic framework for solid-phase microextraction of organochlorine pesticides in vegetable and fruit samples

A covalent organic framework named N-COF was successfully constructed by the aldehyde-amine condensation reaction between 2,4,6-tris (4-formyl phenoxy)-1,3,5-triazine and 1,3-bis(4-aminophenyl) urea for the first time. The prepared N-COF exhibited good stability and high affinity to organochlorine pesticides (OCPs). Thus, the N-COF was served as solid phase microextraction fiber coating for extraction of six OCPs from vegetables and fruits including romaine lettuce, cabbage, Chinese cabbage, apple, pear and peach, followed by quantitation with gas chromatography-electron capture detector (GC-ECD). Under the optimal conditions, good linearities for the OCPs existed in the ranges from 0.1 to 1.0 ng g^-1 to 100.0 ng g^-1 for the samples. The low limits of detection for analytes were obtained in the range of 0.03-0.3 ng g^-1. The present work can offer new alternative for sensitive analysis of trace level of OCPs in vegetables and fruits.

Novel biomass-derived porous-graphitic carbon coated iron oxide nanocomposite as an efficient electrocatalyst for the sensitive detection of rutin (vitamin P) in food and environmental samples

Design and development of inexpensive, portable, and eco-friendly electrochemical non-enzymatic sensors with high selectivity and sensitivity is pivotal in analytical chemistry. In this regard, we have developed a highly porous graphitic-activated carbon (GAC, derived from tamarind fruit shell biomass) coated iron oxide (Fe₂O₃) nanocomposite (Fe₂O₃/GAC) for the efficient detection of rutin (vitamin p). Fe₂O₃/GAC nanocomposite was prepared using a facile green synthesis method and thoroughly characterized using SEM, XRD, and XPS techniques. As-prepared Fe₂O₃/GAC nanocomposite was deposited over a screen printed electrode (SPE) to fabricate Fe₂O₃/GAC/SPE and utilized as a non-enzymatic sensor for the electrochemical determination of rutin in food and environmental samples. The modified electrode was characterized using cyclic voltammetry and electrochemical impedance spectroscopy techniques, which witnessed the excellent conductivity of the developed sensor. The fabricated Fe₂O₃/GAC/SPE nanocomposite exhibited a set of redox peaks in the presence of rutin, corresponding to the electrochemical redox feature of rutin (rutin to 3',4'-diquinone). Further, the modified electrode displayed excellent electrocatalytic characteristics towards the oxidation of rutin, based on which a differential pulse voltammetry-based sensor was developed for rutin determination. The developed non-enzymatic sensor has shown prominent performance towards rutin detection in a wide linear range from 0.1 to 130 μM with an excellent detection limit of 0.027 μM. The enhanced electrocatalytic response could be ascribed to the synergistic effect of Fe₂O₃ and GAC on the developed probe. Moreover, the developed sensor was successfully utilized for real-time detection of rutin in various samples.

A selective sensing platform for the simultaneous detection of ascorbic acid, dopamine, and uric acid based on AuNPs/carboxylated COFs/Poly(fuchsin basic) film

In this study, an electrochemical sensing strategy was developed based on the synergies of gold nanoparticles (AuNPs) doped carboxylated covalent organic frameworks (ACOFs) and poly(fuchsin basic) film for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). This strategy not only took advantage of the adopted materials but also made use of the H-bonding and electrostatic interaction between the three compounds and materials. For this sensing, a poly-BFu film was formed on the surface of bare glass carbon electrode (GCE) under a constant potential. AuNPs was highly dispersed and immobilized on the constructed ACOF-TaTp to obtain AuNPs@ACOF. The constructed sensor AuNPs@ACOF/p-BFu/GCE combined the merits of high surface area, hydrophilicity, conductivity, and selective affinity, consequently exhibiting high sensitivity and selectivity toward the simultaneous detection of AA, DA, and UA with wide linear response ranges of 25-1500 μM, 0.75-40 μM, and 1-200 μM, respectively. The corresponding detection limits were 12.0 μM, 0.15 μM, and 0.22 μM. The simultaneous determination of UA in real human urine sample further confirmed the practicability of the designed electrode.

A novel covalent triazine framework developed for efficient determination of 1-naphthol in water

Covalent triazine frameworks (CTFs) are an exciting new class of porous organic materials with excellent chemical stability and easy functionalization. In recent years, CTFs have gained increasing attention in electrochemical detection of environmental contaminants. Herein, a novel CTF material was successfully synthesized by the solvothermal condensation of 1,3,5-tris-(4-aminophenyl)triazine (TAPT) and 2,3,6,7-tetrabromonapthalene dianhydride (TBNDA) for determination of 1-naphthol in water. The obtained CTF, denoted here as TATB, comprised uniformly sized spherical particles (diameter 0.5-2 μm) with a highly conjugated structure that benefited electron transfer processes when applied to a glassy carbon electrode (GCE). A TATB/GCE working electrode showed excellent catalytic activity for the oxidation of 1-naphthol, with the oxidation peak current being directly proportional to the 1-naphthol concentration in the range of 0.01-10.0 μM, with a detection limit of 5.0 nM (S/N = 3). In addition, the TATB/GCE sensor possesses excellent reproducibility, sensitivity, and selectivity for 1-naphthol determination in aqueous solution. This work highlights the potential of CTFs in electrochemical sensing, whilst also demonstrating a sensitive and stable sensor platform for 1-naphthol detection in water.

Magnetic Solid Phase Extraction Based on Nanostructured Magnetic Porous Porphyrin Organic Polymer for Simultaneous Extraction and Preconcentration of Neonicotinoid Insecticides From Surface Water

In this study, a magnetic porphyrin-based porous organic polymer (MP-POP) nanocomposite was successfully synthesized according previous studies and applied as an adsorbent for simultaneous extraction and preconcentration of four neonicotinoid insecticides from surface river water. The MP-POP was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), N₂-adsorption/desorption analysis, Fourier Transform infrared spectroscopy (FTIR). The neonicotinoid insecticides were quantified using high performance chromatography coupled with diode array detector (HPLC-DAD). The MP-POP shown to have a high surface area, highly porous structure and strong affinity toward the investigated analytes. The adsorption capacities were 99.0, 85.5, 90.0, and 79.4 mg g⁻¹ for acetamiprid, clothiandin, thiacloprid and imidacloprid, respectively. The influential parameters affecting the magmatic μ-solid phase extraction (M-μ-SPE) procedure were investigated using fractional factorial design and surface response methodology (RSM). Under optimum conditions, the method exhibited relatively low limit of detection in the range of 1.3–3.2 ng L⁻¹, limit of quantification in the range of 4.3–11 ng L⁻¹ and wide linearity (up to 600 μg L⁻¹). The intraday and interday precision, expressed as the relative standard deviation (RSD) were <5%. The percentage recoveries for the four target analytes ranged from 91 to 99.3% for the spiked river water samples. The method was applied for determination of neonicotinoids in river water samples and concentrations ranged from 0 to 190 ng L⁻¹.

A dual-functional urea-linked conjugated porous polymer anchoring silver nanoparticles for highly efficient CO2 conversion under mild conditions

A dual-functional urea-linked conjugated porous polymer (UCPP) assembled by enol-imine with ordered unit arrays that act as potential anchoring sites in the networks was fabricated, and was further applied as a support for Ag nanoparticles by the coordinate interaction between them. The UCPP not only can well confine the Ag particle size and facilitate high dispersion, but also can afford special CO₂-philic moieties to enhance the adsorption properties. The resulting Ag@UCPP as a heterogeneous catalyst exhibited excellent activity for the carboxylative cyclization of propargyl alcohols with CO₂ under mild conditions, together with good recyclability, which is probably attributed to the synergistic effect of the UCPP on the adsorption and activation of CO₂ and the immobilization of Ag nanoparticles. This work affords possible opportunities for the design and synthesis of a heterogeneous catalyst toward CO₂ conversion.

Porous Organic Polymers with Thiourea Linkages (POP-TUs): Effective and Recyclable Organocatalysts for the Michael Reaction

As novel porous organic polymers with thiourea linkages, POP-TUs were successfully synthesized with tris(4-aminophenyl) amine (TAA) and 1,4-phenylene diisothiocyanate (PDT) under different conditions. The as-synthesized POP-TUs possess distinctly different morphological characteristics and can effectively catalyze the Michael reaction of trans-β-nitrostyrenes to diethyl malonate. Particularly, the POP-TU-2-catalyzed Michael reaction can proceed smoothly even using an ultralow catalyst dosage of 0.03 mol %, whose turnover number (TON) and turnover frequency (TOF) can reach up to 2700 and 25 h^-1, respectively. Besides, POP-TU-2 also exhibits excellent recyclability and reusability. Only 2% decline in the isolated yield was found after five consecutive runs. This work shows a significant improvement over previously reported thiourea-based catalysts and can offer an effective strategy for developing highly efficient heterogeneous organocatalysts.

Primary Amine-Functionalized Mesoporous Phenolic Resin-Supported Palladium Nanoparticles as an Effective and Stable Catalyst for Water-Medium Suzuki-Miyaura Coupling Reactions

Metal nanoparticles have been recognized and widely explored as unique catalysts for carbon-carbon coupling reactions. However, due to their extreme tendency to agglomeration, the generation and stabilization of metal nanoparticles in a porous matrix is an important research field. Herein, novel mesoporous phenolic resin-supported palladium nanoparticles (Pd@NH₂-MPRNs) were prepared via direct anionic exchange followed by gentle reduction by using primary amine-functionalized ordered mesoporous phenolic resin as the support. The obtained Pd@NH₂-MPRN material still possessed large surface area and ordered two-dimensional hexagonal mesoporous structure. Meanwhile, uniform and well-dispersed palladium nanoparticles were formed in the mesoporous channels, which could be attributed to an efficient complexation and stabilization effect derived from the primary amine groups. As a result, it can promote Suzuki coupling of less activated aromatic bromides to various biaryls in water with high conversion and selectivity. This excellent performance was attributed to small particle sizes, ordered mesopores, and a hydrophobic pore surface, which resulted in the decreased diffusion limitation and the increased active site accessibility. It is noted that it is competitive with the best palladium catalysts known for water-medium Suzuki coupling reaction, and it can be reused at least seven times without significant reduction in the catalytic efficiency, showing a good recyclability. Therefore, this work provides a new potential platform for designing and fabricating robust ordered mesoporous-polymer-supported metal nanoparticles for various catalytic applications.

Ultrafine and highly dispersed platinum nanoparticles confined in a triazinyl-containing porous organic polymer for catalytic applications

The fabrication of stable porous organic polymers (POPs) with heteroatoms that can firmly anchor noble metal nanoparticles (NPs) is a challenging and significant task for heterogeneous catalysis. In the current work, we used piperazine and cyanuric chloride as precursors and successfully fabricated a PC-POP material. Then, through the impregnation method and subsequently the reduction method, ultrafine Pt NPs were confined in the PC-POP with a high dispersion. The Pt NP active sites are accessible due to the uniform mesopores of the PC-POP that facilitate diffusion and mass transfer. The organic cages and nitrogen atoms in the PC-POP frameworks can make the Pt NPs stably anchored in the PC-POP during the catalytic process. The obtained Pt@PC-POP nanocatalyst showed excellent catalytic activity and good recyclability in the selective hydrogenation of halogenated nitrobenzenes and catalytic hydrolysis of ammonia borane as compared with many other reported noble metal catalysts.