Search

Covalent organic frameworks (COFs), newly developed materials, exhibit considerable promise in the field of catalysis. COFs exhibit captivating catalytic characteristics, including thermal and chemical stability, customizable porosities, and the ability to place active sites flexibly with tunable functions. To establish a connection between structure and activity, this paper provides a thorough justification of the planned creation of covalent organic frameworks for photocatalysis, encompassing H2 production, carbon dioxide reduction, pollutants reduction and transformation of organic substances. We have investigated the catalytic sites that are active within covalent organic frameworks, encompassing the metals, molecular catalysts, and catalyst with single atom (SACs); the reactive skeleton/linkages; and the reactive pendant groups. This exploration aims to establish the benefits of using COF‐based catalysts compared to traditional catalysts. Despite the new advantages, numerous difficulties have also been noted with regard to the future. The objective of this review is to make it easier to design COF‐based composite materials for practical uses. [ABSTRACT FROM AUTHOR]

Polyurethane coatings were synthesized through polyaddition polymerization using various polyols. These polyols included polypropylene glycol with different molecular weights, such as PPG-2000, and PPG-1200, as well as 1,4-butanediol. Additionally different contents of bisphenol F; namely 4.5, 11.5, and 24.2%, as well as methylene diphenyl diisocyanate at an NCO/OH ratio of 2.0. The prepolymer polyurethane films were analyzed to study their characteristics using techniques such as Fourier transform infrared spectroscopy, viscosity measurements, thixotropic index analysis, and mechanical property evaluations. The pot life and dry times of polyurethane coating containing 11.5% bisphenol F were 90 minutes and 10 hours (time to touch), respectively, with full hardening achieved at 28 hours. Furthermore, the coating exhibited excellent mechanical properties: tensile strength of 80 N/m², elongation of 260%, adhesion strength of 10 MPa (crosshatch), hardness of 95, and a contact angle of 118°. These properties, coupled with its strong adhesion (10 MPa) to metal surfaces, contributed to its outstanding chemical and corrosion resistance. The coatings obtained from the prepolymer polyurethane based on 11.5% bisphenol F exhibited the highest mechanical properties and water, chemical, and corrosion resistance followed by 4.5%, and 24.2%, respectively. [ABSTRACT FROM AUTHOR]

Electrocatalytic hydrogen generation in alkaline medium has become widely used in a variety of sectors. However, the possibility for additional performance improvement is hampered by slow kinetics. Because of this restriction, careful control over processes such as water dissociation, hydroxyl desorption and hydrogen recombination is required. Covalent organic frameworks (COFs) based on porphyrin and polyoxometalates (POMs) show encouraging electrocatalytic performance, offering a viable route for effective and sustainable hydrogen generation. Their specific architectures lead to increased electrocatalytic activity, which makes them excellent choices for developing water electrolysis as a clean energy conversion method in the alkaline medium. In this regard, TTris@ZnPor and Lindqvist POM were coordinated to create a new eco-friendly and highly active covalent organic framework (TP@VL-COF). In order to describe TP@VL-COF, extensive structural and morphological investigations were carried out through FTIR, 1H NMR, elemental analysis, SEM, fluorescence, UV-visible, PXRD, CV, N2-adsorption isotherm, TGA and DSC analyses. In an alkaline medium, the electrocatalytic capability of 20%C/Pt, TTris@ZnPor, Lindqvist POM and TP@VL-COF was explored and compared for the hydrogen evolution reaction (HER). The TP@VL-COF showed the best catalytic efficiency for HER in an alkaline electrolyte, requiring just a 75 mV overpotential to drive 10 mA cm−2 and outperforming 20%C/Pt, TTris@ZnPor, Lindqvist POM and other reported catalysts. The Tafel slope value also indicates faster kinetics for TP@VL-COF (114 mV dec−1) than for 20%C/Pt (182 mV dec−1) TTris@ZnPor (116 mV dec−1) and Lindqvist POM (125 mV dec−1). [ABSTRACT FROM AUTHOR]

A simple method for the determination of paracetamol (acetaminophen) with sodium 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium using flow injection analysis (FIA) was developed and validated. The effect of variables such as flow rate, NQS concentration, reaction coil length, NaOH concentration, and detection wavelength were studied. Linear response was found over the concentration range 3–35 mg L−1(r2 = 0.9995), the relative standard deviation from replicate injections (n = 9) of 20 mg L−1of paracetamol was 0.89%. A sampling rate of 82 samples h−1was obtained. The method was applied for the determination of paracetamol in pharmaceutical tablets, and results have been compared with those obtained by the official method. [ABSTRACT FROM AUTHOR]

A mononuclear cobalt(ii) complex [C 5 H 8 N 3 ] 2 [CoCl 4 (C 5 H 7 N 3 ) 2 ] (I) was synthesized and structurally characterized. Single crystal X-ray diffraction analysis indicates that monometallic Co(ii) ions acted as coordination nodes in a distorted octahedral geometry, giving rise to a supramolecular architecture. The latter is made up of a ½ unit form composed of an anionic element [Co 0.5 Cl 2 (C 5 H 7 N 3 )] - and one 2-amino-4-methylpyrimidinium cation [C 5 H 8 N 3 ] + . The crystalline arrangement of this compound adopts the sandwich form where inorganic parts are sandwiched between the organic sheets following the [100] direction. More information regarding the structure hierarchy has been supplied based on Hirshfeld surface analysis; the X⋯H (X = N, Cl) interactions play a crucial role in stabilizing the self-assembly process of I, complemented by the intervention of π⋯π electrostatic interaction created between organic entities. Thermal analyses were carried out to study the thermal behavior process. Static magnetic measurements and ab initio calculations of compound I revealed the easy-axis anisotropy character of the central Co(ii) ion. Two-channel field-induced slow-magnetic relaxation was observed; the high-frequency channel is characterized by underbarrier relaxation with U eff = 16.5 cm -1 , and the low-frequency channel involves a direct relaxation process affected by the phonon-bottleneck effect., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Electrocatalytic hydrogen generation in alkaline medium has become widely used in a variety of sectors. However, the possibility for additional performance improvement is hampered by slow kinetics. Because of this restriction, careful control over processes such as water dissociation, hydroxyl desorption and hydrogen recombination is required. Covalent organic frameworks (COFs) based on porphyrin and polyoxometalates (POMs) show encouraging electrocatalytic performance, offering a viable route for effective and sustainable hydrogen generation. Their specific architectures lead to increased electrocatalytic activity, which makes them excellent choices for developing water electrolysis as a clean energy conversion method in the alkaline medium. In this regard, TTris@ZnPor and Lindqvist POM were coordinated to create a new eco-friendly and highly active covalent organic framework (TP@VL-COF). In order to describe TP@VL-COF, extensive structural and morphological investigations were carried out through FTIR, 1 H NMR, elemental analysis, SEM, fluorescence, UV-visible, PXRD, CV, N 2 -adsorption isotherm, TGA and DSC analyses. In an alkaline medium, the electrocatalytic capability of 20%C/Pt, TTris@ZnPor, Lindqvist POM and TP@VL-COF was explored and compared for the hydrogen evolution reaction (HER). The TP@VL-COF showed the best catalytic efficiency for HER in an alkaline electrolyte, requiring just a 75 mV overpotential to drive 10 mA cm -2 and outperforming 20%C/Pt, TTris@ZnPor, Lindqvist POM and other reported catalysts. The Tafel slope value also indicates faster kinetics for TP@VL-COF (114 mV dec -1 ) than for 20%C/Pt (182 mV dec -1 ) TTris@ZnPor (116 mV dec -1 ) and Lindqvist POM (125 mV dec -1 ).

In the title compound, C(15)H(14)N(2)O(4), the N=C double bond has an E configuration. The two benzene rings make a dihedral angle of 28.59 (6)°. In the crystal, mol-ecules are linked into a three-dimensional network by inter-molecular N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds and stabilized by weak C-H⋯π inter-actions.