This study is aimed to elucidate the deep intuitive understanding of whether carboxyl groups of graphene oxide (GO) are worth modifying for the selective oxidation of benzyl alcohol (BzA) to benzaldehyde (BzH). In this work, for the first time, Cu-salen complex (Where Salen = N,N'-bis(4-hydroxysalicylaldehyde)ethylenediamine) was grafted on chloro- modified GO nanosheets forming a heterogeneous catalyst (Cu-f-GO). First principles-based density functional theory (DFT) has been performed to inspect structural and electronic properties, binding mechanism of SOCl2 with each available functional group of GO. Besides, other parameters like HOMO, LUMO, energy bandgap (Eg), adsorption energy (E-ad), electronegativity (chi), chemical potential (mu), and global electrophilicity were also calculated. The catalytic results show that the as-prepared catalyst demonstrated petite performance. This poor performance might be due to lesser acidic sites available on the surface of the catalyst. Hence, it was decided to substantiate the hypothesis, we have conducted the catalytic reaction using a few drops of concentrated H2SO4 as a precursor. The use of precursor had resulted in optimal activity with 100% conversion and 98.64% selectivity to BzH within 1 h. (C) 2021 Elsevier B.V. All rights reserved.

Here in this article, we report an eco-friendly approach for in situ synthesis of MNPs implanted on reduced graphene oxide (MNPs@rGO) [where MNPs = Metal nanoparticles such as vanadium oxide (VO), Nickel (Ni) and Copper (Cu)] nanocatalysts. These composite materials were well corroborated through diverse physicochemical techniques. Noticeably, MNPs@rGO promoted hydrogenolysis of benzyl alcohol (BzA) with triethylsilane (Et3SiH) as a reductant bestowing exceptional activity to provide synthetically valuable hydrocarbon product i.e. toluene. The impact of discrete experimental variables like mole ratio, catalyst amount, reaction time and solvents have also been examined. Under the optimized conditions, CuNPs@rGO exclusively promoted the preceding reaction leading to 81.2% conversion of BzA with 99.9% toluene selectivity. Additionally, it could be recycled and reused without consequential loss of activity in the fifth cycle tests.

Abstract Carbon, being a material of the era, has vast usefulness in the synthesis of many novel compounds. One of them is graphene quantum dots (GQDs) have drawn a great deal of attention to the scientific community owing to their low cytotoxicity, higher optical stability, and tremendous photoluminescence (PL) property, which show a new insight in the field of bio-sensing and bio-imaging. Herein, we have demonstrated a facile method to synthesise N-doped GQDs from graphene oxide (GO) using solvothermal treatment with aprotic solvent. GO was synthesised using a modified Hummers’ method. The as-prepared N-GQDs showed stronger green emission with 326 nm wavelength. PL study showed that PL characteristics of as-synthesised N-GQDs are mainly due to the surface π→π* and n→π* transitions of N containing functional groups with skeletal carbons of the graphene oxide sheet. The N-GQDs were also examined for bio-imaging of microbial cells including E. coli and Saccharomyces cescerevisiae yeast. The results (blue and green emissions under a fluorescence microscope) of this study showed biocompatibility and the photostability of N-GQDs for their application in the fields ranging from energy to biomedicine.

In these days, conservation of the environment is the vital theme of the globe. For that green materials are being discovered to a greater extent. By dint of exclusive properties like optical and electronic properties, water solubility, exceptional biocompatibility, low toxicity and influential chemical inertness of carbon nanodots (CDs) have been extensively investigated systematically and applied in many fields. One can increase the applicability of photostable and biocompatible CDs by doping of nitrogen, sulfur and/or other organic or inorganic materials. In particular, CDs are at present intensifying as a class of potential fluorescent explore in account of their low photobleaching and versatile surfaces. In this review article, we discuss a range of "green" sources along with diverse synthetic routes and photo- and electron properties of this unique material and also provide further insight for improvement in their functionality using various dopants and arouse further research into their potential applications, such as photovoltaics, bioimaging, nanodots-sensitized solar cells, energy conversion, optoelectronics, supercapacitor and light-emitting devices. For each topic, the most relevant end results reported in the literature are accessed with some considerations on the future perspectives.

Novel hybrid bifunctional FeNPs/PPD@rGO for Knoevenagel condensation reaction with 100% conversion and yield.

Oxidation of norbornene was carried out over oxovanadium Schiff base complex grafted on –OH and –COOH modified graphene oxide (GO) as heterogeneous catalysts using 30% H2O2 as an oxidant and ethylene glycol as a solvent. Amongst them, the carboxylic acid group modified GO was found to be better for this transformation. The lower conversion with –OH modified catalyst was ascribed to the higher acidic nature of the catalyst. NH3-TPD study confirmed the less acidic sites on the –COOH modified catalyst and this less acidic nature and controlled addition of 30% H2O2 became the centre of action for this catalytic transformation. Absolute conversion of norbornene (100%) with 98.8% 2,3-epoxy norbornane was achieved at 60 °C in 1 h. This catalyst was recycled four times without significant loss of activity. This durability of the catalyst was believed to be due to strong π–π stacking interaction of GO sheet and an unsaturated ring of ligand and cyclic structure of ligand which protect the metal to leach out.

Graphene oxide (GO) supported transition metal complexes are apprised as sturdy and everlasting heterogeneous catalysts. GO surface was functionalized with 3-triethoxysilylpropylamine (TSPA) and this amino functionalized GO (A-f-GO) nanocomposite with vanadyl Schiff base complex (VO-f-GO) was prepared and to give credence of its potentiality, it was chosen for the selective epoxidation of styrene using environmentally benign 30% H2O2 to styrene oxide (SO). To evade the detrimental exposure of "inborn" water, a selective high boiling and potent hygroscopic solvent, ethylene glycol was chosen to make this transformation productively successful. With the assistance of theoretical studies, we have probed the effect of H2O2 on to structural properties, binding mechanism and electronic properties of the catalyst and substrate. Adsorption energy (E-ad), energy band gap (E-g) and HOMO-LUMO were also calculated. Based on DFT calculations, resonance Raman and UV/Vis studies, we confirmed the formation of metal-peroxo species and propose the plausible catalytic pathway. The influence of the diverse experimental parameters, like substrate to oxidant mole ratio, catalyst concentration, type of solvents, solvent amount, time, temperature and oxidant were tested. A clear relationship was found between different reaction parameters like solvent amount, oxidant, catalyst concentration and temperature etc. and product distribution. This heterogeneous catalyst yielded styrene oxide as nearly the sole product (selectivity = 98.7%) with a conversion value of 99.2% in the oxidation of styrene with hydrogen peroxide in ethylene glycol.

Nowadays, green materials are being discovered to a greater extent to conserve the environment.

A chemo-selective oxidation of benzyl alcohol (BzA) to benzaldehyde (BzH) was built up using transition metal immobilized amino functionalized graphene oxide [ML-f-GO (M = VO4+, Co2+, Cu2+)] as heterogeneous catalysts. Surface hydroxyl groups on GO are engaged fundamentally in the fabrication of ML-f-GO, was confirmed by density functional theory (DFT), Fourier-Transform Infrared (FTIR), electronic spectra and X-ray photoelectron spectroscopy (XPS) results, besides these X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brauner-Emmett-Teller (BET) results, Raman, scanning electron microscope (SEM) and transmission electron microscopy (TEM) were employed to corroborate the successful fabrication. DFT study was executed in an attempt to elucidate the replacement of hydroxyl groups by amino groups. The propensity of binding energy was COOH > COC>NH2 > OH which very well corroborate the belief developed from different characterization techniques that the amino groups of substituted amino functionalized moiety replace only surface hydroxyl groups of GO. Energy gap, global hardness and softness were also calculated. Catalytic aptitude of the as-prepared catalysts was weigh-up against oxidation of BzA using 30% H2O2 as a greener oxidant. The impact of distinct parameters influencing catalytic activity has also been studied. Under the optimized conditions, CuL-f-GO exclusively promoted this transformation with excellent activity to yield 99.5% BzH.

Transition metal (M = VO(IV) and/or Co(Il)] complexes with Schiff base ligand (2)-3-methyl-1-pheny1-4-(2,2,2-trifluoro-1-(2-hydroxyphenyl)imino)ethyl)-1H-pyrazol-5-ol (H2L) have been entrapped in the super cages of zeolite-Y by Flexible Ligand Method. These nanohybrid materials have been characterized by preferential physico-chemical techniques such as ICP-OES, elemental analyses, (FT-IR, H-1 and C-13-NMR and electronic) spectral studies, BET, scanning electron micrographs (SEMs), AAS, X-ray diffraction patterns (XRD) and thermogravimetric analysis. The density functional theory calculations are performed to find optimized structures together with the bond angles, bond lengths, dihedral angles and electronic properties of ligand and neat complexes. The catalytic competence of zeolite-Y entrapped metallo-pyrazole complexes was examined by the oxidation of olefins viz. limonene, cyclohexene, styrene, and a-pinene using H2O2 as an oxidant. So as to ensure the shielding effect of the nanohybrid over the active center on the catalytic properties, the performance of the entrapped complexes (heterogeneous system) was weighing up against the neat complexes (homogeneous system). The effect of experimental variables (such as solvents, mole ratio of substrate and oxidant, the amount of catalyst and reaction time) with their probable justification on the conversion of limonene was discussed. Under the optimized reaction conditions, [VO(L)center dot H2O]center dot Y was found to be potential candidate, achieving 87.44%, 90.01%, 82.01%, and 85.44% conversions of limonene, cyclohexene, styrene, and a-pinene oxidation reactions, respectively.

We demonstrate the infiltration of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) skeleton within robust Co metal loaded mesoporous zeolites viz. Co/ZSM-5 and/or Co/HY to prepare the ([BMIM]BF4@Co/ZSM-5) and/or ([BMIM]BF4@Co/HY) host–guest systems and characterized by various physico–chemical techniques. The catalytic activity of these catalysts was investigated in the liquid phase Baeyer–Villiger (BV) oxidation of cyclohexanone under solvent-free condition. Amongst them, [BMIM]BF4@Co/HY was found to be potential candidate by showing excellent performance with 54.88% conversion of cyclohexanone and 86.36% ε-caprolactone selectivity with elevated TOF and TON values of 4312.43 h−1 and 25874.58, respectively. In addition to this, the host–guest system could be successfully recycled six times without significant loss of activity.

Transition metal [M = VO (IV) and/or Cu (II)] complexes with Schiff base ligand, (Z)-2-((2-hydroxybenzylideneamino)phenol (H 2 L) have been entrapped in the super cages of zeolite-Y by Flexible Ligand Method. Synthesized materials have been characterized by preferential physico-chemical techniques such as inductively coupled plasma optical emission spectroscopy (ICP-OES), elemental analyses (CHN), fourier transmission infrared spectroscopy (FTIR), electronic and UV-reflectance spectra, Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron micrographs (SEMs), X-ray diffraction patterns (XRD) and thermogravimetric analysis (TGA). The catalytic competence of zeolite-Y entrapped transition metal complexes was examined in Baeyer-Villiger (BV) oxidation of cyclopentanone using 30% H 2 O 2 as an oxidant beside neat complexes to check the aptitude of heterogeneous catalysis over the homogeneous system. The effect of experimental variables such as mole ratio of substrate to an oxidant, amount of catalyst, reaction time, varying oxidants and solvents on the conversion of cyclopentanone was also tested. Under the optimized reaction conditions, one of the zeolite-Y entrapped transition metal complex viz. [VO(L)H 2 O]-Y [where L = (Z)-2-((2-hydroxybenzylideneamino)phenol] was found to be a potential contender by providing 80.22% conversion of cyclopentanone (TON: 10479.42), and the selectivity towards δ-valerolactone was 83.56%.