Correlation between the microstructures of graphite oxides and their catalytic behaviors in air oxidation of benzyl alcohol

Chitosan-derived mesoporous N-doped carbon catalyst embedded with NiO for highly selective benzyl alcohol oxidation

MOF-derived heteroatom-doped mesoporous carbons have gained the significant consideration in heterogenous catalytic reactions because of their multipurpose features. Especially, the high Specific Surface Area (SSA) of these materials provides abundant activated sites for the catalytic reactions, while the mesoporous structure allows for the effective mass transfer, enhancing the overall capability of the catalytic process. Herein, the efficient NiO/CN-T (T referred to the pyrolysis temperature) was prepared by facile pyrolysis of MOF/CS composite (Ni-MOF (74), Chitosan) in the presence of excess amount of starch as the carbon precursor. The NiO/CN-T as heterogenous catalyst has desired SSA varied from 1094 to 491 m2.g-1. The optimized catalyst (NiO/CN-600) possesses the superior catalytic activity toward the oxidation of the BnOHs due to its high SSA (1094 m2.g-1), which can notably rectify the mass transfer proficiency. Additionally, the NiO/CN-600 heterogenous catalyst also represents the acceptable chemical stability. So, it was demonstrated that such an innovative strategy can provide several versatile tunability insights for the preparation of MOF/biopolymer-derived heterogenous catalysts.

A DFT investigation of the catalytic oxidation of benzyl alcohol using graphene oxide

CONTEXT

Metal-free heterogeneous materials have attracted great interest due to their potential to facilitate various organic transformations in line with circular economy and green chemistry principles. Among various 2D materials, graphene oxide (GO) is considered an attractive material for numerous applications in physics, chemistry, biology, material sciences, and catalysis. Furthermore, graphene-based catalysts exhibit good catalytic activity toward the selective oxidation of benzyl alcohol to benzaldehyde or benzoic acid under eco-friendly conditions. In this regard, a theoretical investigation was carried out to study both catalytic oxidation reaction pathways (i.e., benzyl alcohols to aldehyde and to benzoic acid) using GO as an eco-friendly and metal-free catalyst.

METHODS

In this study, we report a theoretical investigation at the B3LYP/6-31G level to better understand the oxidation of benzyl alcohol using GO as a metal-free catalyst. The possible bond formation was investigated using the global and local reactivity indexes derived from Fukui functions. Furthermore, we performed a non-covalent interaction (NCI) analysis to unveil the stability and the interaction nature between both reagents and GO surface. The effect of the solvent on the oxidation efficiency was also performed and the results indicate that the solvent significantly affects the decrease of reactivity by increasing the activation barriers through oxidation reactions of benzyl alcohol. Additionally, the electron localization function (ELF) analysis was performed for all intermediates showing the ionic nature of the studied epoxide structure of GO and rules out any type of covalent interaction during the oxidation reaction of benzyl alcohol. All these obtained results are in good agreement with experimental observations and reveal that the epoxide functions on the graphene surface promote an excellent catalyst turnover.

Effectiveness of Nonfunctionalized Graphene Oxide Nanolayers as Nanomedicine against Colon, Cervical, and Breast Cancer Cells

Recent studies in nanomedicine have intensively explored the prospective applications of surface-tailored graphene oxide (GO) as anticancer entity. However, the efficacy of nonfunctionalized graphene oxide nanolayers (GRO-NLs) as an anticancer agent is less explored. In this study, we report the synthesis of GRO-NLs and their in vitro anticancer potential in breast (MCF-7), colon (HT-29), and cervical (HeLa) cancer cells. GRO-NLs-treated HT-29, HeLa, and MCF-7 cells showed cytotoxicity in the MTT and NRU assays via defects in mitochondrial functions and lysosomal activity. HT-29, HeLa, and MCF-7 cells treated with GRO-NLs exhibited substantial elevations in ROS, disturbances of the mitochondrial membrane potential, an influx of Ca²⁺, and apoptosis. The qPCR quantification showed the upregulation of caspase 3, caspase 9, bax, and SOD1 genes in GRO-NLs-treated cells. Western blotting showed the depletion of P21, P53, and CDC25C proteins in the above cancer cell lines after GRO-NLs treatment, indicating its function as a mutagen to induce mutation in the P53 gene, thereby affecting P53 protein and downstream effectors P21 and CDC25C. In addition, there may be a mechanism other than P53 mutation that controls P53 dysfunction. We conclude that nonfunctionalized GRO-NLs exhibit prospective biomedical application as a putative anticancer entity against colon, cervical, and breast cancers.

Biomass-derived porous carbon with high drug adsorption capacity undergoes enzymatic and chemical degradation

Degradability is a key safety issue when choosing materials for biomedical applications and environmental protection. This factor greatly limits the application of porous carbon in these areas due to the inert and stable nature of carbon network. In this work, this conflict could be well-resolved by rational designing a mesoporous carbon (MC) with biomass as a carbon source. The retained oxygen-containing species simultaneously increase drug adsorption capacity and the degradability of MC. The maximum adsorption quantity for doxorubicin over MC can reach 395.3 mg/g, about 3-fold over carbon nanotubes. The detailed analysis reveals that the degradation of MC occurs via a radical mediated oxidation process. The high electron density feature of MC facilitates the electrophilic addition reaction in the presence of HO. During this process, the carbon network is gradually degraded into fragments, carbon nanodots and ultimately to CO₂. This work opens up a new way to fabricate degradable porous materials and provides a promising material for the practical application in biomedical and environmental field.

Wearable Crop Sensor Based on Nano-Graphene Oxide for Noninvasive Real-Time Monitoring of Plant Water

Real-time noninvasive monitoring of crop water information is an important basis for water-saving irrigation and precise management. Nano-electronic technology has the potential to enable smart plant sensors to communicate with electronic devices and promote the automatic and accurate distribution of water, fertilizer, and medicine to improve crop productivity. In this work, we present a new flexible graphene oxide (GO)-based noninvasive crop water sensor with high sensitivity, fast responsibility and good bio-interface compatibility. The humidity monitoring sensitivity of the sensor reached 7945 Ω/% RH, and the response time was 20.3 s. We first present the correlation monitoring of crop physiological characteristics by using flexible wearable sensors and photosynthesis systems, and have studied the response and synergistic effect of net photosynthetic rate and transpiration rate of maize plants under different light environments. Results show that in situ real-time sensing of plant transpiration was realized, and the internal water transportation within plants could be monitored dynamically. The synergistic effect of net photosynthetic rate and transpiration of maize plants can be jointly tested. This study provides a new technical method to carry out quantitative monitoring of crop water in the entire life cycle and build smart irrigation systems. Moreover, it holds great potential in studying individual plant biology and could provide basic support to carry out precise monitoring of crop physiological information.

Solventless Mechanochemical Fabrication of ZnO–MnCO3/N-Doped Graphene Nanocomposite: Efficacious and Recoverable Catalyst for Selective Aerobic Dehydrogenation of Alcohols under Alkali-Free Conditions

Catalytic efficacy of metal-based catalysts can be significantly enhanced by doping graphene or its derivatives in the catalytic protocol. In continuation of previous work regarding the catalytic properties of highly-reduced graphene oxide (HRG), graphene-oxide (GO) doped mixed metal oxide-based nanocomposites, herein we report a simple, straightforward and solventless mechanochemical preparation of N-doped graphene (NDG)/mixed metal oxide-based nanocomposites of ZnO–MnCO3 (i.e., ZnO–MnCO3/(X%-NDG)), wherein N-doped graphene (NDG) is employed as a dopant. The nanocomposites were prepared by physical milling of separately fabricated NDG and ZnO–MnCO3 calcined at 300 °C through eco-friendly ball mill procedure. The as-obtained samples were characterized via X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Raman, Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and surface area analysis techniques. To explore the effectiveness of the obtained materials, liquid-phase dehydrogenation of benzyl alcohol (BOH) to benzaldehyde (BH) was chosen as a benchmark reaction using eco-friendly oxidant (O2) without adding any harmful surfactants or additives. During the systematic investigation of reaction, it was revealed that the ZnO–MnCO3/NDG catalyst exhibited very distinct specific-activity (80 mmol/h.g) with a 100% BOH conversion and <99% selectivity towards BH in a very short time. The mechanochemically synthesized NDG-based nanocomposite showed remarkable enhancement in the catalytic performance and increased surface area compared with the catalyst without graphene (i.e., ZnO–MnCO3). Under the optimum catalytic conditions, the catalyst successfully transformed various aromatic, heterocyclic, allylic, primary, secondary and aliphatic alcohols to their respective ketones and aldehydes with high selectively and convertibility without over-oxidation to acids. In addition, the ZnO–MnCO3/NDG was also recycled up to six times with no apparent loss in its efficacy.

Eco-Friendly and Solvent-Less Mechanochemical Synthesis of ZrO2–MnCO3/N-Doped Graphene Nanocomposites: A Highly Efficacious Catalyst for Base-Free Aerobic Oxidation of Various Types of Alcohols

In recent years, the development of green mechanochemical processes for the synthesis of new catalysts with higher catalytic efficacy and selectivity has received manifest interest. In continuation of our previous study, in which graphene oxide (GRO) and highly reduced graphene oxide (HRG) based nanocomposites were prepared and assessed, herein, we have explored a facile and solvent-less mechanochemical approach for the synthesis of N-doped graphene (NDG)/mixed metal oxide (MnCO3–ZrO2) ((X%)NDG/MnCO3–ZrO2), as the (X%)NDG/MnCO3–ZrO2 nano-composite was synthesized using physical grinding of separately synthesized NDG and pre-calcined (300 °C) MnCO3–ZrO2 via green milling method. The structures of the prepared materials were characterized in detail using X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), Raman, Thermogravimetric analysis (TGA), and N2 adsorption-desorption isotherm analysis. Besides, the obtained nanocomposites were employed as heterogeneous oxidation catalyst for the alcohol oxidation using green oxidant O2 without involving any surfactants or bases. The reaction factors were systematically studied during the oxidation of benzyl alcohol (PhCH2OH) as the model reactant to benzaldehyde (PhCHO). The NDG/MnCO3–ZrO2 exhibits premium specific activity (66.7 mmol·g−1·h−1) with 100% conversion of PhCH2OH and > 99.9% selectivity to PhCHO after only 6 min. The mechanochemically prepared NDG based nanocomposite exhibited notable improvement in the catalytic efficacy as well as the surface area compared to the pristine MnCO3–ZrO2. Under the optimal circumstances, the NDG/MnCO3–ZrO2 catalyst could selectively catalyze the aerobic oxidation of a broad array of alcohols to carbonyls with full convertibility without over-oxidized side products like acids. The NDG/MnCO3–ZrO2 catalyst were efficiently reused for six subsequent recycling reactions with a marginal decline in performance and selectivity.

Eco-Friendly Mechanochemical Preparation of Ag2O–MnO2/Graphene Oxide Nanocomposite: An Efficient and Reusable Catalyst for the Base-Free, Aerial Oxidation of Alcohols

Recently, the development of eco-friendly mechanochemical approaches for the preparation of novel catalysts with enhanced activity and selectivity has gained considerable attention. Herein, we developed a rapid and solvent-less mechanochemical method for the preparation of mixed metal oxide (Ag2O–MnO2) decorated graphene oxide (GRO)-based nanocomposites (Ag2O–MnO2/(X wt.%)GRO), as the Ag2O–MnO2/(X wt.%)GRO nanocomposite was fabricated by the physical grinding of freshly prepared GRO and pre-annealed (300 °C) mixed metal oxide nanoparticles (NPs) (Ag2O–MnO2) using an eco-friendly milling procedure. The as-prepared nanocatalysts were characterized by using various techniques. Furthermore, the nanocomposites were applied as a heterogeneous catalyst for the oxidation of alcohol by employing gaseous O2 as an eco-friendly oxidant under base-free conditions. The mechanochemically obtained GRO-based composite exhibited noticeable enhancement in the surface area and catalytic performance compared to the pristine Ag2O–MnO2. The results revealed that (1%)Ag2O–MnO2/(5 wt.%)GRO catalyst exhibited higher specific performance (13.3 mmol·g−1·h−1) with a 100% conversion of benzyl alcohol (BnOH) and >99% selectivity towards benzaldehyde (BnH) within 30 min. The enhancement of the activity and selectivity of GRO-based nanocatalyst was attributed to the presence of various oxygen-containing functional groups, a large number of defects, and a high specific surface area of GRO. In addition, the as-prepared nanocatalyst also demonstrated excellent catalytic activity towards the conversion of a variety of other alcohols to respective carbonyls under optimal conditions. Besides, the catalyst ((1%)Ag2O–MnO2/(5 wt.%)GRO) could be efficiently recycled six times with no noticeable loss in its performance and selectivity.

A Facile Synthesis of ZrOx-MnCO3/Graphene Oxide (GRO) Nanocomposites for the Oxidation of Alcohols using Molecular Oxygen under Base Free Conditions

Graphene and its nanocomposites are showing excellent potential in improving the catalytic performances of different materials. However, the synthetic protocol and its form, such as graphene oxide (GRO) or highly reduced graphene oxide (HRG), influence the catalytic efficiencies. Here, we present, a facile synthesis of graphene oxide (GRO) and ZrOx-MnCO3-based nanocomposites [(1%)ZrOx–MnCO3/(x%)GRO] and their outcome as an oxidation catalyst for alcohol oxidation under mild conditions using O2 as a clean oxidant. The ZrOx–MnCO3/GRO catalyst prepared by incorporating GRO to pre-calcined ZrOx-MnCO3 using ball milling showed remarkable enhancement in the catalytic activities as compared to pristine ZrOx–MnCO3, ZrOx–MnCO3 supported on HRG or ZrOx–MnCO3/GRO prepared by in-situ growth of ZrOx–MnCO3 onto GRO followed by calcination. The catalyst with composition (1%)ZrOx–MnCO3/(1%)GRO exhibited superior specific activity (57.1 mmol/g·h) with complete conversion and >99% selectivity of the product within a short period of time (7 min) and at a relatively lower temperature (100 °C). The catalyst could be recycled at least five times with a negligible decrease in efficiency and selectivity. The catalytic study was extended to different aromatic as well as aliphatic alcohols under optimized conditions, which confirmed the efficiency and selectivity of the catalyst.

Study on the performance and mechanism of aerobic oxidative desulfurization based on a dual-functional material possessing catalytic and adsorptive properties

Herein, three polyoxometalates, namely K₃PW₁₂O₄₀·10H₂O, K₆[α-P₂W₁₈O₆₂]·14H₂O, and K₈H[P₂W₁₅V₃O₆₂]·9H₂O, were successfully prepared and used in the air/n-octanaloxidative desulfurization (ODS) system.

Facile synthesis of ultrafine cobalt oxides embedded into N-doped carbon with superior activity in hydrogenation of 4-nitrophenol

Design and synthesis of low-cost catalysts with high activity and stability for hydrogenation reactions is an important research area of applied catalysis. In this work, we present a kind of ultrafine cobalt oxides encapsulated by N-doped carbon (donated as CoO_x/CN) as efficient catalysts for hydrogenation of 4-nitrophenol (4-NP) process. The CoO_x/CN was fabricated through a pyrolysis strategy using an N-containing metal-organic framework (Co-MOF) as precursor followed by a fine thermal-treatment. With an optimized pyrolysis temperature of 500 °C, the CoO_x species present as ultrafine particles highly dispersed in the obtained catalyst (CoO_x/CN-500). CoO_x/CN-500 exhibits excellent activity and stability in hydrogenation of 4-NP at ambient conditions. The activity is much higher than that of not only bulk cobalt oxides, but also carbon supported CoO_x catalysts. It could be used for more than 8 times without obvious fading in activity. In addition, the concrete role of Co-MOF precursor and pyrolysis condition in the catalyst design was investigated in detail. The interaction between organic ligands and Co ions and the confinement of the crystalline structure of Co-MOF could restrain the aggregation of Co ions during pyrolysis and lead to high dispersion of ultrafine CoO_x species. Meanwhile, the N-containing ligands could be transformed into doped N species (pyridinic and pyrrolic N), endowing the CoO_x species with high electron density and promoting the formation of active sites for the hydrogenation reaction.

A highly reduced graphene oxide/ZrOx–MnCO3 or –Mn2O3 nanocomposite as an efficient catalyst for selective aerial oxidation of benzylic alcohols

ZrOx(1%)–MnCO₃/HRG(1%) based nanocomposites material as an efficient oxidation catalyst.

New photosensitive nanometric graphite oxide composites as antimicrobial material with prolonged action

A new conjugate material based on partially reduced graphite oxide (rGO), silver nanoparticles (Ag), and bis(lysinato)zirconium(IV) phthalocyanine complex (ZrPc) was obtained. Its optical properties (absorption and photoluminescence) after dispersion in solvents were examined. The antimicrobial properties were tested to determine the effect of the composite on the following bacterial strains: Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, which are responsible for many infections and are one of the pathogens the most difficult to treatment. The results obtained for rGO-ZrPc-Ag composite were compared with the properties of GO, GO-ZrPc, and rGO-Ag structures. The influence of the near-infrared irradiation on the antimicrobial activity of ZrPc- and Ag-doped materials against bacteria was observed for very low concentration (0.32mg/mL) of GO-ZrPc to stop the growth of P. aeruginosa in comparison to the nonirradiated sample (41mg/mL). The usefulness of this material in therapy, such as wound infection treatment or endodontic treatment, as antibacterial agent with sustained action was discussed.

Application of metal organic frameworks M(bdc)(ted)0.5 (M = Co, Zn, Ni, Cu) in the oxidation of benzyl alcohol

The selective oxidation of benzyl alcohol to benzaldehyde is an important process in heterogeneous catalysis and green organic chemistry.

Hierarchical porous carbon materials with high capacitance derived from Schiff-base networks

A type of hierarchical porous carbon material was prepared using a Schiff-base network as the precursor and ZnCl2 as the activation agent, and their electrochemical performances were investigated in acid and alkaline aqueous solutions, respectively. The as-prepared materials have high surface areas, appropriate distributions of hierarchical pore sizes, and various forms of nitrogen/oxygen derivatives. These structural advantages guarantee the outstanding performances of such carbon materials as electrodes for supercapacitors, which include high specific capacitances, fast current responses, and high cycling stabilities.

Rational design of carbon support to prepare ultrafine iron oxide catalysts for air oxidation of alcohols

The efficient carbon supports change not only the physical but also the chemical properties of iron oxide and create new active sites for the enhancement of catalytic activity in the oxidation of alcohols with air as an oxygen source.

Hybrid Ni–Al layered double hydroxide/graphene composite supported gold nanoparticles for aerobic selective oxidation of benzyl alcohol

A NiAl-LDH/RGO composite-supported Au catalyst was synthesized and exhibited high activity and stability in the selective oxidation of benzyl alcohol.