Synthesis and characterization of cobalt-supported catalysts on modified magnetic nanoparticle: Green and highly efficient heterogeneous nanocatalyst for selective oxidation of ethylbenzene, cyclohexene and oximes with molecular oxygen

Green and efficient catalytic oxidation of ethylbenzene to acetophenone over cobalt oxide supported on a carbon material derived from sugar

The use of biomass as a carbon source to support metal oxides has significant advantages in environmental protection and reducing the cost of the catalyst. The critical point lies on the development of highly active and recyclable catalysts. In this study, sugar was used as a carbon source, and cobalt oxide was loaded via an in situ method and an impregnation method to prepare the catalyst, respectively. The catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, Raman, in situ electron paramagnetic resonance (in situ EPR) and N2 adsorption-desorption. The characterization results show that the macroporous carbon-supported cobalt oxide catalyst prepared by the in situ method contains CoOx nanoparticles on the support, but the dispersion of cobalt oxide on the support is more uniform compared with the catalyst prepared by the impregnation method. The catalytic performance of the prepared catalyst was evaluated through the oxidation of ethylbenzene (EB) to acetophenone (AP) as a probe reaction. Under the optimized reaction conditions, temperature (T) = 80 °C, m(catalyst) : m(EB) = 0.15, n(H2O2) : n(EB) : n(KBr) = 14.4 : 1 : 0.1, t = 8 h, and V(EB) : V(CH3COOH) = 1 : 10, the conversion of EB and the selectivity of AP were 84.1% and 81.3%, respectively. CoOx/SC-10-in situ exhibits improved reactivity of EB oxidation owing to cobalt ions on the carbon support that promote the free radical and acid catalytic reaction pathway. The cobalt oxide catalyst supported by biomass carbon has decent recycling and regeneration ability, which provides a new idea for the application of biomass.

Nanoarchitectonics of vanadium nanoparticles decorated mesoporous carbon nitride in photocatalytic systems: A study on ethylbenzene oxidation reaction

In this work, we have described the synthesis of vanadium (V) nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (V@mpg-C3N4) and their uses in photocatalytic ethylbenzene oxidation to the respective acetophenones. The mpg-C3N4 serves as the support for the decoration of V NPs, through a simple impregnation method. Various advanced techniques, such as XRD, UV-vis spectrometry, HRTEM, HAADF-STEM, AC-STEM, elemental mapping, and BET surface area analysis, were employed for the characterization of V@mpg-C3N4. The detailed characterization studies reveal that the V@mpg-C3N4 catalyst has a medium band gap (2.78 eV), a high surface area (76.7 m2g-1), and a mesoporous nature. The V@mpg-C3N4 photocatalysts demonstrated excellent performance in the light-assisted oxidation of ethylbenzene, achieving over 99 % conversion and selectivity for acetophenone in an environmentally friendly solvent (water) using a domestic light source (50 W white light). This developed synthesis strategy will be useful for synthesizing various noble and non-noble metal-based catalysts and their applications in organic transformation and environmental remediation.

Enhanced PMS/O2 activation by self-crosslinked amine-gluteraldehyde/chitosan-Cu biocomposites for efficient degradation of HEPES as biological pollutants and selective allylic oxidation of cyclohexene

Optimization and mechanism elucidation of the catalytic degradation of HEPES and selective aerobic oxidation of cyclohexene by Cu@cross-linked magnetic chitosan.

Valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment: Approaching green chemistry and circular economy principles

Water pollution is one of the most critical issues worldwide and is a priority in all scientific agendas. Green nanotechnology presents a plethora of promising avenues for wastewater treatment. This review discusses the current trends in the valorization of zero-cost, biodegradable, and readily available agro-industrial biowaste to produce green bio-nanocatalysts and bio-nanosorbents for wastewater treatment. The promising roles of green bio-nanocatalysts and bio-nanosorbents in removing organic and inorganic water contaminants are discussed. The potent antimicrobial activity of bio-derived nanodisinfectants against water-borne pathogenic microbes is reviewed. The bioactive molecules involved in the chelation and tailoring of green synthesized nanomaterials are highlighted along with the mechanisms involved. Furthermore, this review emphasizes how the valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment adheres to the fundamental principles of green chemistry, circular economy, nexus thinking, and zero-waste manufacturing. The potential economic, environmental, and health impacts of valorizing agro-industrial biowaste to green nanomaterials are highlighted. The challenges and future outlooks for the management of agro-industrial biowaste and safe application of green nanomaterials for wastewater treatment are summarized.

Transition Metal Salts of Carboxylated Multiwalled Carbon Nanotubes in Combination with N-hydroxyphthalimide as Catalytic Systems for Hydrocarbon Oxidation

In this study, the transition metal (Co (II), Cu (II), and Mn (II)) salts of carboxylated carbon nanotubes were synthesized and characterized (the determined metal contents were in the range of 0.89-1.16%). The catalytic activity and the possibility for recovery and reuse of the obtained heterogeneous salts were then studied in the solvent-free oxidation of ethylbenzene with oxygen. The oxidation processes were carried out at 80 °C under atmospheric pressure in the presence of N-hydroxyphthalimide. The highest conversion of ethylbenzene, 27%, was obtained with a system consisting of the Cu (II) salt of the carboxylated carbon nanotubes, N-hydroxyphthalimide, and the azo initiator AIBN.

Covalent anchoring of N-hydroxyphthalimide on silica via robust imide bonds as a reusable catalyst for the selective aerobic oxidation of ethylbenzene to acetophenone

N-Hydroxyphthalimide is anchored on commercial silica by robust imide bonds, and the synthesized N-oxyl catalysts exhibit excellent activity, selectivity and reusability for the aerobic oxidation of ethylbenzene to acetophenone.

Synthetic Tuning of CoII-Doped Silica Nanoarchitecture Towards Electrochemical Sensing Ability

The present work introduces both synthesis of silica nanoparticles doped with CoII ions by means of differently modified microemulsion water-in-oil (w/o) and Stöber techniques and characterization of the hybrid nanoparticles (CoII@SiO2) by TEM, DLS, XRD, ICP-EOS, SAXS, UV-Vis, and UV-Vis/DR spectroscopy and electrochemical methods. The results reveal the lack of nanocrystalline dopants inside the hybrid nanoparticles, as well as no ligands, when CoII ions are added to the synthetic mixtures as CoII(bpy)3 complexes, thus pointing to coordination of CoII ions with Si-O- groups as main driving force of the doping. The UV-Vis/DR spectra of CoII@SiO2 in the range of d-d transitions indicate that Stöber synthesis in greater extent than the w/o one stabilizes tetrahedral CoII ions versus the octahedral ions. Both cobalt content and homogeneity of the CoII distribution within CoII@SiO2 are greatly influenced by the synthetic technique. The electrochemical behavior of CoII@SiO2 is manifested by one oxidation and two reduction steps, which provide the basis for electrochemical response on glyphosate and HP(O)(OEt)2 with the LOD = 0.1 μM and the linearity within 0.1-80 μM. The Stöber CoII@SiO2 are able to discriminate glyphosate from HP(O)(OEt)2, while the w/o nanoparticles are more efficient but nonselective sensors on the toxicants.

Hierarchical hollow nickel silicate microflowers for selective oxidation of styrene

Developing heterogeneous non-precious metal catalysts that can achieve high catalytic activity and good product selectivity at the same time is still a challenging and interesting work for the selective oxidation of styrene into valuable chemicals from environmental and industrial points of view. Herein, hierarchical hollow nickel silicate (Ni₃Si₂O₅(OH)₄) microflowers assembled from well-defined Ni₃Si₂O₅(OH)₄ nanosheets have been prepared by a facile one-pot hydrothermal method. The intriguing structure endows the hollow Ni₃Si₂O₅(OH)₄ microflowers a high surface area of 177.4 m² g^-1 and an average pore size of 3.9 nm. When employed as a catalyst for the selective oxidation of styrene in the presence of hydrogen peroxide as a ecological sustainable green oxidant, the Ni₃Si₂O₅(OH)₄ exhibits an attractive catalytic performance with a remarkably high styrene conversion of 99.3% and a high selectivity of 81.1% to benzaldehyde.

Synthesis, crystal structure and immobilization of a new cobalt(ii) complex with a 2,4,6-tris(2-pyridyl)-1,3,5-triazine ligand on modified magnetic nanoparticles as a catalyst for the oxidation of alkanes

A new Co(ii) complex with formula [Co(tptz)Cl₂]·2H₂O (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) has been synthesized and characterized, followed by being supported on modified magnetic nanoparticles as a catalyst for the oxidation of alkanes.

A 3D-honeycomb-like catalyst: a nitrogen-doped carbon material with cobalt and manganese-oxide for C–H bond oxidation

A three dimensional mesoporous honeycomb-like material that is multifunctional and easily recoverable, and shows efficient performance is described.

Organoselenium–palladium(ii) complex immobilized on functionalized magnetic nanoparticles as a promising retrievable nanocatalyst for the “phosphine-free” Heck–Mizoroki coupling reaction

An air- and moisture-stable organoselenium–palladium complex immobilized on silica-coated magnetic nanoparticles is designed, synthesized and applied as a practical and retrievable catalyst in the Heck–Mizoroki cross-coupling reaction.