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Visible light assisted photocatalytic transformations have been considered as an efficient and sustainable approach for the production of high-value chemicals. The present paper describes the synthesis of plasmonic silver nanoparticle incorporated reduced graphene oxide and its photocatalytic performance for the selective oxidation of various benzylamines to the corresponding imines using molecular oxygen as an oxidant under ambient temperature conditions. The developed photocatalyst was found to be highly stable and exhibited excellent photoactivity with a consistent recycling ability for several runs without a loss in activity. Moreover, to the best of our knowledge, the developed photocatalyst represents the first example of a graphene-based photocatalyst for the oxidative coupling of amines. [ABSTRACT FROM AUTHOR]

Abstract: We describe a simple, cost‐effective, efficient, and high‐yielding photocatalytic approach for the oxidative self‐dimerization of 2‐naphthols using a semiconductor–metal hybrid that consists of intercalated manganese dioxide nanoparticles in reduced graphene oxide (rGO/MnO2) under visible‐light irradiation. The desired photocatalyst was synthesized in a single step by mixing MnO2 nanoparticles with rGO ultrasonically. The hybrid photocatalyst exhibited a significantly higher activity than neat MnO2 nanoparticles and rGO, which is believed to be because of the synergistic effect of its components. To our knowledge, this hybrid rGO/MnO2 nanocomposite is the first heterogeneous, green photocatalyst for the oxidative coupling of 2‐naphthols under mild conditions. [ABSTRACT FROM AUTHOR]

Nitrogen doped reduced graphene oxide (N-rGO), 5.8% N readily synthesized from the thermal annealing of graphene oxide (GO) in ammonium hydroxide at 453 K, was demonstrated to be a superior metal-free non-acidic carbo-catalyst for the esterification of fatty acids with different alcohols. The effect of various reaction parameters such as reaction temperature, reaction time, catalyst amount etc. has been studied. The developed catalyst was found to be highly stable and exhibited consistent reusability for seven cycles without any significant decrease in the product yields. [ABSTRACT FROM AUTHOR]

A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation [ABSTRACT FROM AUTHOR]

The octahedral molybdenum cluster-based compound, Cs2Mo6Bri8Bra6 was immobilized on graphene oxide (GO) by using a facile approach. High resolution transmission electron microscopy results revealed that molybdenum clusters were uniformly distributed on the GO nanosheets. Cs2Mo6Bri8Bra6 was attached to the GO support via chemical interaction between apical ligands of Mo6Bri8Bra6 cluster units and oxygen functionalities of GO, as revealed by XPS studies. The developed material was used for the synthesis of dimethyl carbonate by reduction of carbon dioxide. The synthesized catalyst, that is, GO-Cs2Mo6Bri8Bra x, exhibited higher catalytic efficiency than its homogeneous analogue without using dehydrating agent. The catalyst was found to be efficiently recyclable without significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

A rhenium-oxo complex such as methyltrioxorhenium (MTO) has been homogeneously immobilized on a Schiff base modified graphene oxide (GrO) support via covalent bonding. The loading of MTO on GrO nanosheets was monitored by FTIR, TG-DTA, and elemental analyses. The developed heterogeneous catalyst is found to be efficient for the oxidation of various amines to the corresponding N-oxides using hydrogen peroxide as an oxidant in high to excellent yields. At the end of the reaction, the catalyst is readily recovered by filtration and reused for subsequent runs. After the third run, the catalyst showed a marginal decrease in catalytic activity owing to the leaching of the MTO complex from the support. [ABSTRACT FROM AUTHOR]

New graphene oxide (GO)-tethered-CoII phthalocyanine complex [CoPc-GO] was synthesized by a stepwise procedure and demonstrated to be an efficient, cost-effective and recyclable photocatalyst for the reduction of carbon dioxide to produce methanol as the main product. The developed GO-immobilized CoPc was characterized by X-ray diffraction (XRD), FTIR, XPS, Raman, diffusion reflection UV/Vis spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). FTIR, XPS, Raman, UV/Vis and ICP-AES along with elemental analysis data showed that CoII-Pc complex was successfully grafted on GO. The prepared catalyst was used for the photocatalytic reduction of carbon dioxide by using water as a solvent and triethylamine as the sacrificial donor. Methanol was obtained as the major reaction product along with the formation of minor amount of CO (0.82 %). It was found that GO-grafted CoPc exhibited higher photocatalytic activity than homogeneous CoPc, as well as GO, and showed good recoverability without significant leaching during the reaction. Quantitative determination of methanol was done by GC flame-ionization detector (FID), and verification of product was done by NMR spectroscopy. The yield of methanol after 48 h of reaction by using GO-CoPc catalyst in the presence of sacrificial donor triethylamine was found to be 3781.8881 μmol g−1 cat., and the conversion rate was found to be 78.7893 μmol g−1cat. h−1. After the photoreduction experiment, the catalyst was easily recovered by filtration and reused for the subsequent recycling experiment without significant change in the catalytic efficiency. [ABSTRACT FROM AUTHOR]

Well-dispersed iron nanoparticles supported on chemically derived graphene oxide containing uniform distribution of iron nanoparticles (FeNPs) throughout the surface was synthesized and was used as a heterogeneous catalyst for oxidative cyanation of tertiary amines to the corresponding α-aminonitriles in high to excellent yields using hydrogen peroxide with sodium cyanide in acetic acid. After the reaction the catalyst could easily be separated by the influence of an external magnet and reused for several runs without any significant change in the catalytic activity and without leaching of the metal during the reaction. [ABSTRACT FROM AUTHOR]

Photocatalytic conversion of carbon dioxide to valuable chemicals by using semiconductor materials is one of the major challenges in materials science. Higher efficiency and product yield can be achieved by designing of a suitable photocatalyst with retarded recombination of photogenerated electron-hole pair and sufficient potential for the reduction of CO 2. In this work, unique composite architecture of graphene-oxide wrapped TiO 2 nanotubes for the photocatalytic reduction of CO 2 has been developed. The TiO 2 nanotubes formed by electrochemical anodization are wrapped with graphene oxide/reduced graphene oxide (GO/rGO) layers which also form interconnecting bridges between the adjacent nanotubes. Such a unique nanostructure helped the separation of photogenerated electron-hole pairs with better charge transfer to perform the reduction of adsorbed CO 2 molecules. The rGO/TiO 2 multi-leg nanotubes (MLNTs) have shown the highest photocatalytic activity with maximum yield of CO c.a. 1348 μmol g−1 within the first 20 min, which stabilize to about 760 μmol g−1 after 2 h of UV-A irradiation. More importantly, the CO formation rate is about an order of magnitude higher than that from graphene supported TiO 2 nanocrystals. Unlabelled Image • A unique nanostructure in the form of graphene oxide wrapped TiO 2 nanotubes have been used to carry out photocatalytic CO 2 reduction • Detailed 'blank' experiments confirmed the product formation is solely from feed gas CO 2 and not due to decomposition of graphene oxide • Selective CO formation is obtained with values about an order of magnitude higher that the previously reported data. [ABSTRACT FROM AUTHOR]

A highly efficient, recyclable and magnetically separable core-shell structured CuZnO@Fe 3 O 4 microsphere wrapped with reduced graphene oxide (rGO@CuZnO@Fe 3 O 4 ) photocatalyst has been developed and used for the photoreduction of carbon dioxide with water to produce methanol under visible light irradiation. Owing to the synergistic effect of the components and to the presence of a thin Fe 2 O 3 layer on Fe 3 O 4 , rGO@CuZnO@Fe 3 O 4 4 exhibited higher catalytic activity as compared to the other possible combinations such as CuZnO@Fe 3 O 4 2 and GO@CuZnO@Fe 3 O 4 3 microspheres. The yield of methanol in case of using 2 and 3 as photocatalyst was found to be 858 and 1749 μmol g −1 cat, respectively. However, the yield was increased to 2656 μmol g −1 cat when rGO@CuZnO@Fe 3 O 4 4 was used as photocatalyst under similar experimental conditions. This superior photocatalytic activity of 4 was assumed to be due to the restoration of the sp 2 hybridized aromatic system in rGO, which facilitated the movement of electrons and resulted in better charge separation. The synthesized heterogeneous photocatalyst could readily be recovered by external magnet and successfully reused for six subsequent cycles without significant loss in the product yield. [ABSTRACT FROM AUTHOR]

Nickel oxide nanoparticles were grafted on reduced graphene oxide via simultaneous reduction of graphene oxide and nickel salt in a single step reaction. The synthesized material (rGO/NiO) was found to be efficient visible light active photocatalyst for the reduction of nitroaromatic derivatives to their corresponding amino compounds. Hydrazine monohydrate provided necessary protons and electrons for the targeted reaction. After completion of the reaction, the photocatalyst could readily be recovered by simple external magnet and could be reused for six runs without any significant loss of its activity. More importantly, the photocatalyst did not show any leaching during the reaction as confirmed by ICP-AES analysis of the recovered catalyst. [ABSTRACT FROM AUTHOR]

Visible-light-induced photocatalytic reduction of aromatic nitrobenzenes to the corresponding anilines at room temperature using reduced graphene oxide (rGO) immobilized iron(II) bipyridine complex as photocatalyst is described. The rGO-immobilized iron catalyst exhibited superior catalytic activity than homogeneous iron(II) bipyridine complex and much higher than metal free rGO photocatalysts. The heterogeneous photocatalyst was found to be robust and could easily be recovered and reused for several runs without any significant loss in photocatalytic activity. [ABSTRACT FROM AUTHOR]

A novel graphene oxide (GO)-immobilized heteroleptic iridium complex was synthesized and demonstrated as a first heterogenized homogeneous catalyst for the production of dimethylformamide (DMF) from carbon dioxide, hydrogen, and dimethylamine. The synthesized hybrid catalyst showed comparable activity as homogeneous heteroleptic iridium complex with additional benefits such as facile recovery and recycling of the catalyst. After completion of the reaction, the heterogeneous catalyst was easily recovered by filtration, and reused for subsequent recycling processes without any significant change in the catalytic efficiency. [ABSTRACT FROM AUTHOR]

A ternary hybrid of graphene oxide-titania-polystyrene (GO-TiO 2 -PS) nanocomposite is developed where polystyrene composition is regulated by controlling growth of polymer chains and nanoarchitectonics is discussed. Graphene Oxide-TiO 2 (GO-TiO 2 ) nanocomposite is prepared by in-situ hydrothermal method and the surface is anchored with α-bromoisobutyryl bromide to activate GO-TiO 2 as initiator for polymerization. In-situ grafting of polystyrene through surface initiated atom transfer radical polymerization (SI- ATRP) on this Br-functionalized nano-composite initiator yields GO-TiO 2 -PS ternary hybrid. Varying the monomer amount and keeping the concentration of initiator constant, polystyrene chain growth is regulated with narrow poly-dispersivity to achieve desired composition. This composite is well characterized by various analytical techniques like FTIR, XRD, DSC, SEM, TEM, and TGA. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuO nanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probed by FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is explored for reduction of CO 2 into the methanol under the visible light irradiation. The breadth of CuO nanorods and the oxidation state of Cu in the rGO–CuO/Cu 2 O nanocomposites are systematically varied to investigate their photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owing to fast recombination of charge carriers and yielded 175 μmol g −1 methanol, whereas rGO–Cu 2 O and rGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 μmol g −1 ) and seven (1228 μmol g −1 ) folds methanol, respectively. The superior photocatalytic activity of CuO in the rGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transfer of photo-generated electrons through the rGO skeleton. This study further excludes the use of scavenging donor. [ABSTRACT FROM AUTHOR]

A well dispersed magnetically separable palladium complex immobilized to magnetite–graphene oxide nanocomposite has been synthesized via solvothermal route. The successfully decorated graphene oxide sheets with the homogeneously dispersed iron nanoparticles and palladium(II) complex were proved by transmission electron microscopy. X-ray diffraction pattern of the synthesized catalyst revealed that palladium(II) complex was successfully immobilized to the support. Further, X-ray photoelectron spectroscopy confirmed that palladium is present in +2 oxidation state. The synthesized heterogeneous material was found to be an efficient catalyst for the oxidative esterification of alcohols with methanol by using molecular oxygen as oxidant. The developed catalyst was found to be more reactive than its homogeneous analog, i.e. PdCl 2 (CH 3 CN) 2 . Similarly, no reaction occurred in the presence of Pd(0)/magnetite–graphene nanocomposite catalyst. These studies confirmed that the palladium(II) ions are the main catalyst and superior reactivity of heterogeneous palladium catalyst is attributed to the promotion role of graphene support in the adsorption of reactant alcohol and oxygen. After the reaction, the catalyst was easily separated by external magnetic effect and reused for several runs with consistent catalytic activity without any detectable leaching. [ABSTRACT FROM AUTHOR]

Photoelectrochemical conversion of CO 2 to chemicals has been acknowledged as an advanced and promising approach for the mitigation of carbon dioxide that is a greenhouse gas. However, so far it has mainly been confined to the generation of C1 products like formate, CO, methanol etc. and very few reports are known on the generation of ethanol or higher alcohols. The present work described an efficient PEC reduction of CO 2 to ethanol selectively by using a photocathode consisting of a ternary composite containing CuxO/GO and a copper-based metal-organic framework (Cu-MOF). The maximum ethanol yield was found to be 162 uM cm−2 after 4 h at an applied potential of -0.5 V vs Ag/AgCl. The better charge separation, higher mobility and density of photogenerated charge carriers on the interface of nanocomposite led to the higher availability of photo-electrons for CO 2 reduction that is further confirmed by the DFT studies. Furthermore, DFT calculations suggested the binding of CO 2 over GO/Cu x O/Cu-BTC surface via Cu-atoms through the vertical orientation that brought the CO 2 molecules closer to the composite and therefore is considered as the most favourable adsorption configuration. [ABSTRACT FROM AUTHOR]