Fine-Tuning of Ni/NiO over H-NbOx for Enhanced Eugenol Hydrogenation through Enhanced Oxygen Vacancies and Synergistic Participation of Active Sites.

The hydrogenation of lignin-derived phenolics to produce valuable chemicals is a promising but challenging task. This study successfully demonstrates the use of sustainable transition metal-based catalysts to hydrogenate lignin-derived phenolics. A defect-induced oxygen vacancy containing H-NbOx prepared from commercial Nb2O5 was employed as a catalyst. H-NbOx exhibited higher oxygen vacancies (158.21 µmol/g) than commercial Nb2O5 (39.01 µmol/g), evaluated from O2-TPD. Upon supporting 10 wt % Ni, a Ni/NiO interface was formed over H-NbOx, which was intrinsically active for the hydrogenation of phenolics. 10Ni/H-NbOx exhibited a two-fold increase in activity than 10Ni/Nb2O5, achieving >99% eugenol conversion and affording ∼94% 4-propyl cyclohexanol selectivity, wherein ∼63% eugenol conversion and ∼73% 4-propyl cyclohexanol selectivity were obtained over 10Ni/Nb2O5. The Ni/NiO formation was confirmed by X-ray photoelectron spectroscopy, HR-TEM, and H2-TPR analysis, while the oxygen vacancies were verified by Raman spectroscopy and O2-TPD analysis. The resulting interface enhanced the synergy between Ni and H-NbOx and facilitated hydrogen dissociation, confirmed by H2-TPD. Remarkably, 10Ni/H-NbOx maintained its catalytic activity for five tested cycles and demonstrated exceptional activity with various phenolics. Our findings highlight the potential of a sustainable transition metal catalyst for the hydrogenation of lignin-derived phenolic compounds, which could pave the path to producing valuable chemicals in an environmentally friendly manner.

Improving the Coke Resistance of Ni-Ceria Catalysts for Partial Oxidation of Methane to Syngas: Experimental and Computational Study.

The synthesis of syngas (H2 : CO=2) via catalytic partial oxidation of methane (CPOM) is studied over noble metal doped Ni-CeO2 bimetallic catalysts for CPOM reaction. The catalysts were synthesized via a controlled deposition approach and were characterized using XRD, BET-surface area analysis, H2 -TPR, TEM, Raman and TGA analysis. The catalysts were experimentally and computationally studied for their activity, selectivity, and long-term stability. Although the pure 5Ni/CeO2 catalyst showed high initial activity (∼90%) of CH4 conversion, it rapidly deactivates around 20% of its initial activity within 140 hours of TOS. Doping of Ni/CeO2 catalyst with noble metal was found to be coke resistant with the best-performing Ni-Pt/CeO2 catalyst showed ∼95% methane conversion with >90% selectivity at a temperature of 800 °C, having exceptional stability for about 300 hours of time-on-stream (TOS). DFT studies were performed to calculate the activation barrier for the C-H activation of methane over the Ni, Ni3 Pt, Ni3 Pd, and Ni3 Ru (111) surfaces showed nearly equal activation energy over all the studied surfaces. DFT studies showed high coke formation tendency of the pure Ni (111) having a very small C-C coupling activation barrier (14.2 kJ/mol). In contrast, the Ni3 Pt, Ni3 Pd, and Ni3 Ru (111) surfaces show appreciably higher C-C coupling activation barrier (∼70 kJ/mol) and hence are more resistant against coke formation as observed in the experiments. The combined experimental and DFT study showed Ni-Pt/CeO2 as a promising CPOM catalyst for producing syngas with high conversion, selectivity and long-term stability suited for future industrial applications.

Visible Light-Driven Metal-Organic Framework-Mediated Activation and Utilization of CO2 for the Thiocarboxylation of Olefins.

Visible light-mediated photoredox catalysis has emerged to be a fascinating approach for the activation of CO2 and its subsequent fixation into valuable chemicals utilizing renewable and inexhaustible solar energy. Although great progress has been made in CO2 photoreduction, visible light-assisted organic synthesis using CO2 as a reactive substrate is rarely explored. Herein, we report an efficient, facile, and economically viable photoredox-mediated approach for the synthesis of important ß-thioacids via carboxylation of olefins with CO2 and thiols over a porous functionalized metal-organic framework (MOF), Fe-MIL-101-NH2, as a photocatalyst under ambient conditions. This multicomponent reaction offers wide substrate scope, mild reaction conditions, easy work-up, cost-effective and reusable photocatalysts, and higher product selectivity. Computational studies suggested that CO2 interacts with the thiophenol-styrene adduct to facilitate the synthesis of ß-thioacids in almost quantitative yields.

TiO2 supported cobalt oxide for olefin epoxidation reaction - characterization, catalytic activities and mechanism - using a DFT model.

Metal oxide catalysts are known to trigger C-H bond activation selectively, indicating their suitability for olefin epoxidation. Nano-structured Co3O4 supported on TiO2 was prepared for selective epoxidation of a number of olefins under optimized reaction conditions. An appropriate synthetic procedure yielded a catalytic material (Co-Ti (NP)HT) with desired crystal size and interface conditions. Incorporation of Co into the Ti matrix resulted in an enhancement in the specific surface of Ti-Co nanoparticles (77.93 m2 g-1). XPS measurements evaluated the surface cobalt atom concentration (5.77%) in Ti-Co(NP)HT, indicating more dispersion of cobalt oxide species. Catalytic application of the material, using various olefins (under optimized reaction conditions) shows higher conversion (>85%) in a 6-h time interval. The substrate : oxidant (H2O2) concentration in an optimized molar ratio of 1 : 2 shows high olefin conversion for the formation of olefin oxide. The reactivity of olefins was found to be in the order: cyclohexene > methylstyrene > styrene > chlorostyrene > p-nitrostyrene. A DFT model compared the HOMO-LUMO energies of styrene and its substituted forms. The reusability of Ti-Co (NP)HT tested up to four continuous cycles of batch operations indicates a negligible loss (0.25-0.30%) of catalytic activity.

Thermal and photocatalytic cascade one-pot synthesis of secondary amine using multifunctional Pd decorated MOF-derived CeO2.

The use of a single catalyst to perform thermal and photochemical N-alkylation of amine is challenging work. Herein, Pd decorated MOF-derived CeO2 was prepared for the cascade one-pot synthesis of secondary amine by thermal and photocatalytic routes. Among the designed catalysts, Pd(0.5%)/CeO2-300 exhibited the best activity for thermal and photocatalytic one-pot secondary amine synthesis involving benzyl alcohol and aniline. The physicochemical characteristics of Pd(0.5%)/CeO2-300 suited for the oxidation of benzyl alcohol followed by condensation with aniline to form an imine. Further, reduction of imine over Pd NPs decorated on CeO2-300 took place to form secondary amine. An excellent conversion of benzyl alcohol and secondary amine selectivity was observed thermally at 100 °C in 26 h. The Pd(0.5%)/CeO2-300 exhibited excellent activity in white LED. Interestingly, more activity was achieved in sunlight. The Pd(0.5%)/CeO2-300 demonstrated excellent stability under thermal and photocatalytic conditions and was recycled 5 times without losing any significant activity. The surface area, acidity, and elemental compositions were characterized by various physicochemical techniques. The light absorption property, bandgap, charge carrier separation, and photocurrent measurements were carried out by photoelectrochemical and optoelectronic analysis. The reaction mechanism and structural activity relationship correlated with control experiments, catalytic activity data, physicochemical, and optoelectronic characterization. One catalyst affording efficient activity in conventional thermal and photocatalytic conditions, especially sunlight, would be exciting to researchers and industrial practitioners.

Nickel Nanoparticles Immobilized over Mesoporous SBA-15 for Efficient Carbonylative Coupling Reactions Utilizing CO2: A Spotlight.

Ecofriendly routes for the synthesis of carbamates and carbonylative coupling products such as benzyl formate derivatives are very demanding for both academia and industries. Foreseeing a sustainable green future, we systematically analyzed the synthesis history of both these chemicals, mentioning their pros and cons. As a step towards green chemistry, here we have optimized the reaction conditions for the synthesis of various benzyl formates from corresponding benzyl halides and carbamates from substituted anilines and alkyl halides catalyzed by Ni(0) nanoparticles (NPs) immobilized over amine-functionalized ordered mesoporous SBA-15 material in the presence of CO2 as C1 source. This spotlight on applications is aimed to provide a clear outlook to date regarding the gradual progress in the synthesis of both these aforementioned chemicals and finally addresses further efforts for overcoming the current challenges.

Influence of Indium as a Promoter on the Stability and Selectivity of the Nanocrystalline Cu/CeO2 Catalyst for CO2 Hydrogenation to Methanol.

Stable catalyst development for CO2 hydrogenation to methanol is a challenge in catalysis. In this study, indium (In)-promoted Cu nanoparticles supported on nanocrystalline CeO2 catalysts were prepared and explored for methanol production from CO2. In-promoted Cu catalysts with ∼1 wt % In loading showed a methanol production rate of 0.016 mol gCu-1 h-1 with 95% methanol selectivity and no loss of activity for 100 h. It is found that the addition of indium remarkably increases Cu dispersion and decreases Cu particle size. In addition led to an increased metal-support interaction, which stabilizes Cu particles against sintering during the reaction, leading to high stability and activity. In addition, density functional theory calculations suggested that the reaction is proceeding via reverse water gas shift (RWGS) mechanism where the presence of In stabilized intermediate species and lowered CO2 activation energy barriers.

Morphologically controlled cobalt oxide nanoparticles for efficient oxygen evolution reaction.

Electrochemical water oxidation is one of the thrust areas of research today in solving energy and environmental issues. The morphological control in the synthesis of nanomaterials plays a crucial role in designing efficient electrocatalyst. In general, various synthetic parameters can direct the morphology of nanomaterials and often this is the main driving force for the electrocatalyst in tuning the rate of the oxygen evolution reaction (OER) for the electrochemical water-splitting. Here, a facile and cost-effective synthesis of spinel cobalt oxides (Co3O4) via a one-pot hydrothermal pathway with tunable morphology has been demonstrated. Different kinds of morphologies have been obtained by systematically varying the reaction time i.e. nanospheres, hexagon and nanocubes. Their catalytic activity has been explored towards OER in 1.0 M alkaline KOH solution. The catalyst Co3O4-24 h nanoparticles synthesized in 24 h reaction time shows the lowest overpotential (η) value of 296 mV at 10 mA cm-2 current density, in comparison to that of other as-prepared catalysts i.e. Co3O4-pH9 (311 mV), Co3O4-12 h (337 mV), and Co3O4-6 h (342 mV) with reference to commercially available IrO2 (415 mV). Moreover, Co3O4-24 h sample shows the outstanding electrochemical stability up to 25 h time.

Renewable Aromatics from Tree-Borne Oils over Zeolite Catalysts Promoted by Transition Metals.

Despite the ever-growing demand for benzene-toluene-xylene (BTX), the alternative route of production from tree-borne oils is rarely investigated and poorly understood. Here, we have synthesized a Zn-loaded Y-zeolite catalyst for the continuous production of bio-BTX from tree-borne oils (nonedible seed oil), e.g., neem oil. Our approach involves low-temperature selective cracking-dehydrogenation-aromatization of neem oil over metal-supported catalysts to xylene-rich aromatics. The physicochemical properties of the prepared catalyst were characterized using powder XRD, N2 physisorption, TEM, NH3-TPD, XPS, Py-FTIR, solid-NMR, and TG analyses. Mesoporous Y-zeolites with a pore diameter of 7.4 Šshowed better selectivity toward aromatics and were found to be the most effective catalyst for the aromatization process, especially for BTX. The aromatic yield was found to increase with the addition of Zn, and the highest conversion of 90-94% with an ∼75% BTX yield was achieved with the ZnY catalyst. During aromatization, a sizable number of short alkanes and olefins were also obtained on acidic Y-zeolites. The off-gas composition shows the presence of ∼45% C2-C4 olefins with 8.9% H2. The incorporation of Zn species can promote the dehydrogenation activity, and the subsequent aromatization required a suitable pore network. The optimized ZnY catalyst inspires the formation of toluene and xylenes, inhibiting the formation of benzene and gaseous alkanes.

Peptide generated anisotropic gold nanoparticles as efficient siRNA vectors.

Based on the cell penetrating ability of tryptophan-containing peptides, eight linear hexapeptides have been designed, synthesized and explored their efficiency toward the synthesis of gold nanoparticles under sunlight. The peptide generated gold nanoparticles (LP-GNPs) have been characterized by UV-visible spectroscopy, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. The binding ability of LP-GNPs toward siRNA, evaluated by gel electrophoresis indicates that sequence-selective-GNPs without any surface modifications exhibit strong affinity toward negatively charged biomolecules. Cellular uptake studies suggest that LP-GNPs exhibit significant uptake of fluorescence-labeled siRNA inside the cells as evidenced from Fluorescence Microscopy. In vitro gene silencing efficiency using newly generated GNPs revealed that above mentioned LP-GNPs efficiently down-regulate the level of GAPGH gene in colon cancer cells. Comparative gene silencing efficiency results indicate that anisotropic LP7-GNPs exhibit comparable efficacy to other existing carrier systems, such as Lipofectamine 2000 in presence of serum, mimicking in-vivo system. In conclusion, our results demonstrate that peptide-GNPs based delivery system for siRNA emerges to be effective to deliver RNAi therapeutics, uncovering new avenue in oncotherapy.

Functionalized graphene oxide as a nanocarrier for dual drug delivery applications: The synergistic effect of quercetin and gefitinib against ovarian cancer cells.

Graphene Oxide (GO) has been extensively studied in the field of biomedical sciences as one of the most promising biomaterials due to its exceptional physiochemical properties. Experts have long favored anticancer drug cocktails over single drugs, given that the former may provide a more balanced molecular basis for novel chemotherapeutic strategies. Here, we investigated a combinatorial anticancer drug treatment involving the well-proven anticancer drugs quercetin and gefitinib and compared it with gefitinib and quercetin loaded separately onto polyvinylpyrrolidone (PVP)-functionalized graphene oxide (GO-PVP). The loading and cancer cell cytotoxicity of the individual drug systems and their combined loading onto GO-PVP nanovehicles were investigated in PA-1 ovarian cancer cells and compared to their effects on IOSE-364 ovarian epithelial cells. In this report, the combined drug system loaded on the GO-PVP nanovehicle was found to be significantly more toxic than the individual drug loaded systems, as well as the free drugs, toward PA-1 cells compared to the toxicity toward IOSE-364 cells. The combined drug system loaded on the GO-PVP nanovehicle is likely to be more successful than individual drug therapy, given the stronger impact of the combinatorial approach and the efficiency of chemotherapeutic delivery.

Functionalized graphene oxides for drug loading, release and delivery of poorly water soluble anticancer drug: A comparative study.

In this work, the modification of graphene oxides (GOs) have been done with hydrophilic and biodegradable polymer, polyvinylpyrrolidone (PVP) and other excipient ß -cyclodextrin (ß-CD) through covalent functionalization for efficient loading and compatible release of sparingly water soluble aromatic anticancer drug SN-38 (7-ethyl-10-hydroxy camptothecin). The drug was loaded onto both GO-PVP and GO-ß-CD through the π-π interactions.The release of drug from both the nanocarriers were analyzed in different pH medium of pH 7 (water, neutral medium), pH 5 (acidic buffer) and pH 12 (basic buffer). The loading capacity and the cell killing activity of SN-38 loaded on functionalized GO were investigated comprehensively in human breast cancer cells MCF-7.Our findings shown that the cytotoxicity of SN-38 loaded to the polymer modified GO was comparatively higher than free SN-38. In particular, SN-38 loaded GO-PVP nanocarrier has more cytotoxic effect than GO-ß-CD nanocarrier against MCF-7 cells, indicating that SN-38 loaded GO-PVP nanocarrier can be used as promising material for drug delivery and biological applications.

Selective Oxidation of n-Hexane by Cu (II) Nanoclusters Supported on Nanocrystalline Zirconia Catalyst.

Cu (II) nanoclusters supported on nanocrystalline zirconia catalyst (with size ~15 nm), was prepared by using cationic surfactant cetyltrimethylammonium in a hydrothermal synthesis method. The catalyst was characterized by XRD, XPS, TGA, SEM, TEM, FTIR and ICP-AES. The catalyst was found to be efficient in selective oxidation of n-hexane to 2-hexanol. An n-hexane conversion of 55%, with a 2-hexanol selectivity of 70% was achieved over this catalyst in liquid phase, without the use of any solvent. The catalyst can be reused several times without any significant activity loss.

Chloride promoted room temperature preparation of silver nanoparticles on two dimensional tungsten oxide nanoarchitectures for the catalytic oxidation of tertiary N-compounds to N-oxides.

A halide ion promoted two dimensional silver tungsten-based nanomaterial was synthesized by a facile one-pot synthesis protocol at room temperature. The 2D morphology features high activity and selectivity for the oxidation of a wide range of tertiary N-compounds to their corresponding N-oxides. The morphology of Ag/WO3 materials can be varied by changing the synthesis parameters. The unique 2D plate like morphology of tungsten oxide increases adsorption sites of the support, leading to less sintering and higher dispersion of silver nanoparticles, resulting in significantly enhanced activity for the reaction. The influence of reaction parameters such as temperature, substrate to oxidant molar ratio, reaction time, etc. was investigated in detail. The catalyst was characterized by XRD, XPS, ICP-AES, TGA, FT-IR, UV-vis, Raman, SEM, TEM and STEM. Raman studies further provide mechanistic insight which proves that the formation of peroxo tungsten species is responsible for the N-oxidation reaction. High stability and recyclability of the 2D Ag/WO3 nanoplates are also observed under the investigated conditions.

Fabrication of three dimensional (3D) hierarchical Ag/WO3 flower-like catalyst materials for the selective oxidation of m-xylene to isophthalic acid.

A three dimensional (3D) hierarchical silver supported tungsten oxide flower-like microsphere catalyst has been fabricated using a cationic surfactant CTAB. It was found that the crystal-splitting mechanism plays a key role in the formation of this flower-like structure. This catalyst was proved to be highly effective in the liquid phase selective oxidation of m-xylene to isophthalic acid.

Fabrication of three-dimensional (3D) raspberry-like copper chromite spinel catalyst in a facile hydrothermal route and its activity in selective hydroxylation of benzene to phenol.

Three-dimensional (3D) raspberry-like CuCr2O4 spinel nanoparticles were prepared hydrothermally in the presence of cationic surfactant, cetyltrimethylammonium bromide (CTAB). Detailed characterization of the material was carried out by X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). XRD revealed the formation of CuCr2O4 spinel phase, and SEM showed the formation of a 3D raspberry-like structure, composed of 20-50 nm nanoparticles. The raspberry-like particles exhibited excellent catalytic behavior for the hydroxylation of benzene to phenol with H2O2. The influence of reaction parameters were investigated in detail. A benzene conversion of 68.5% with 95% phenol selectivity was achieved at 80 °C. The catalyst did not show any leaching up to 10 reuses, showing the true heterogeneity of the catalyst. However, significant H2O2 decomposition occurs on the catalyst necessitating its use in 5-fold excess.

Direct catalytic oxyamination of benzene to aniline over Cu(II) nanoclusters supported on CuCr2O4 spinel nanoparticles via simultaneous activation of C-H and N-H bonds.

We report the facile synthesis of a highly efficient, reusable catalyst comprising Cu(II) nanoclusters supported on CuCr2O4 spinel nanoparticles for the oxyamination of benzene to aniline (H2O2 + NH3) under mild aqueous reaction conditions. The synergy between the Cu(II) nanoclusters and CuCr2O4 spinel nanoparticles plays the most vital role towards its high catalytic activity.

Cu nanoclusters supported on nanocrystalline SiO2-MnO2: a bifunctional catalyst for the one-step conversion of glycerol to acrylic acid.

A material consisting of highly dispersed Cu nanoclusters anchored on nanocrystalline SiO2-MnO2 has been prepared, and was found to act as a bifunctional catalyst for the one-step conversion of glycerol to acrylic acid using H2O2. Under optimized conditions a glycerol conversion of 77.1%, with 74.7% selectivity for acrylic acid, was achieved after 30 h reaction time.

In situ time-resolved DXAFS for the determination of kinetics of structural changes of H-ZSM-5-supported active Re-cluster catalyst in the direct phenol synthesis from benzene and O2.

Dynamic structural changes and their kinetics of a Re(10)-cluster catalyst in the direct phenol synthesis from benzene and O(2) were investigated by in situ time-resolved Re L(III)-edge energy-dispersive XAFS (DXAFS). We have successfully monitored the structural transformation of active Re(10) clusters to inactive Re monomers in the course of the selective oxidation of benzene with O(2) on the catalyst by the DXAFS technique in a real time. The results obtained suggested that the Re(10) cluster transformed directly to the Re monomers, which showed first order kinetics with respect to the quantity of Re(10) clusters. The absence of undesirable intermediate structures with low phenol selectivity during the structural transformation may be an advantageous issue for the high phenol selectivity of 93.9% at 9.9% conversion in a pulse reaction and 87.7% at 5.8% conversion in a steady-state reaction on the Re(10)-cluster catalyst. The reactant benzene inhibited the unfavorable structural transformation of the Re(10) cluster to the Re monomers during the selective benzene oxidation to phenol.

Low-temperature PROX (preferential oxidation) on novel CeO(2)-supported Cu-cluster catalysts under fuel-cell operating conditions.

Cu(1+)-clusters on a CeO(2) support, which were prepared by hydrothermal synthesis using cetyltrimethylammonium bromide (CTAB), were found to be highly active and selective for preferential oxidation (PROX) of CO in excess H(2) with H(2)O and CO(2) under practical fuel-cell operating conditions.