Showing papers in "New Journal of Chemistry in 2016"

Nitrogen-doped titanium dioxide (N-doped TiO2) for visible light photocatalysis

Abstract: TiO2 is an effective and well-known photocatalyst for water and air purification, but its practical applications in visible light-assisted chemical reactions are hindered mainly by its poor visible light absorption capacity. Nitrogen-doped TiO2 (N-doped TiO2) has attracted considerable attention as a photocatalyst, and rapid progress has been made in enhancing the photocatalytic efficiency of TiO2 under visible light irradiation. N-doped TiO2 exhibits broad absorption in the visible region, which can allow the utilization of a large part of the solar spectrum. This might be useful for environmental and energy applications, such as the photocatalytic degradation of organic pollutants, solar cells, sensors, and water splitting reactions. This review focuses on the major developments in the synthesis of N-doped TiO2 and its possible applications in the photocatalytic degradation of organic pollutants and environmental remediation under visible light irradiation.

Perspectives on zeolite-encapsulated metal nanoparticles and their applications in catalysis

Abstract: Microporous cavities and channels of zeolites frameworks have been used for decades for the encapsulation of cations, complexes and metals. In the particular case of metals, nanoparticles are usually formed after post-synthesis modifications such as ion-exchange or wetness impregnation. Tough encapsulation can provide a strict control of the nanoparticle size as well as a limitation of aggregation at high temperature; encapsulated nanoparticles are often hardly accessible due to diffusion limitations of reactants in sub-nanometric micropores. Recent developments in zeolite synthesis have offered a new class of materials with hierarchical structures or unusual morphologies in which the mean diffusion path is considerably reduced. Those zeolites with inter-crystalline and/or intra-crystalline mesopore systems are particularly adapted for supporting nanoparticles both in microporous cavities of the framework and in mesoporous channels. More sophisticated architectures such as yolk/core–shell materials, in which nanoparticles are protected against poisoning or sintering by a thin zeolite shell, are particularly attractive. In contrast to nanometric intrinsic cavities of zeolite frameworks, a large internal void is available for chemical reactions and such catalysts can be considered as nanoreactors in which the reaction is essentially governed by the permeability of the shell. This review focuses on the most recent progress as well as perspectives in the design of zeolite-containing metal nanoparticles, which differ from traditional materials by the originality of the synthesis method or the morphology of the support.

Diffusion in nanoporous materials: fundamental principles, insights and challenges

Abstract: Following a brief review of Fick's laws and the theory of diffusion in a homogeneous medium, we consider the application of the Fickian model to diffusion in nanoporous materials. If the pore system is statistically uniform the simple Fickian model is directly applicable. Inhomogeneities such as surface or internal barriers require some adjustments to the model but Fick's equations still provide a valid approach. Hierarchical pore systems present a more serious challenge. When there is rapid exchange between the different regions such systems conform to the simple Fickian model, with a diffusivity corresponding to the mean of the diffusivities in the different regions. In contrast, when the condition of rapid exchange is not fulfilled the simple Fickian model is not applicable and the situation becomes more complicated. Simple hierarchical pore structures such as the micropore/macropore system typically found in commercial adsorbents and catalysts can still be described by a dual resistance Fickian model but for more complex hierarchical pore structures Monte Carlo or MD simulations offer the only realistic approach. The measurement of self-diffusion by PFG NMR and by microimaging (notably by interference microscopy) is also reviewed and selected examples are presented to show the detailed information that can be extracted from such measurements, especially when accompanied by molecular simulations. Examples highlighting the relevance of a detailed knowledge of the various steps of mass transfer for a transport-optimized technological application of nanoporous materials, notably for molecular separations and mass conversions, are provided.

Green synthesis of stable and biocompatible fluorescent carbon dots from peanut shells for multicolor living cell imaging

Abstract: A green approach for the synthesis of fluorescent carbon dots (C-dots) with a quantum yield of about 9.91% has been developed using peanut shells as a precursor. The C-dots were prepared via a simple pyrolysis of peanut shells. The obtained C-dots exhibit an excitation-dependent manner, excellent stability, high photostability, and good tolerance for pH, ionic strength and photobleaching. The cytotoxicity of the C-dots was also evaluated using HepG2 cells, and the cell viabilities were estimated to be greater than 90% upon addition of the C-dots over a wide concentration range from 0 to 1.2 mg mL−1. Based on the abovementioned merits, we also applied the prepared C-dots as an effective fluorescent probe for multicolor living cell imaging.

Application of Ni/Co-based metal–organic frameworks (MOFs) as an advanced electrode material for supercapacitors

Abstract: A Ni/Co-based bimetallic metal–organic framework (Ni/Co–MOF) [CoNi(μ3-tp)2(μ2-pyz)2] (tp = terephthalic acid and pyz = pyrazine) was synthesized through a hydrothermal method. Structural characterization revealed that metal centers are equally occupied by Co2+ and Ni2+ ions. The supercapacitive behavior of the synthesized Ni/Co–MOF was evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) measurements in 3 M KOH as electrolyte. The Ni/Co–MOF exhibited an outstanding specific capacitance of 1049 F g−1 at a discharge current density of 1 A g−1, good rate capability (642 F g−1 at 10 A g−1), and 97.4% capacitance retention after 5000 cycles. To the best of our knowledge, this is the first bimetallic MOF that is used in supercapacitors and its encouraging properties indicate that Ni/Co–MOF can be a promising candidate as an advanced electrode material for supercapacitors.

Facilely synthesized N-doped carbon quantum dots with high fluorescent yield for sensing Fe3+

Abstract: Nitrogen doped carbon quantum dots (NCQDs) were synthesized using L-glutamic acid as raw material through a facile, effective and green hydrothermal method in one pot. Without any chemical reagents and further surface modifications, the NCQDs emit bright blue fluorescence with a high quantum yield of 17.8% due to the fluorescence enhancement effect of N dopant atoms on a surface of carbon quantum dots. Moreover, the NCQDs present a sensitive response to Fe3+ ions with a detection limit of 4.67 μM (S/N = 3) through the variation in fluorescence with respect to the target concentration and based on electron transfer from the NCQDs to Fe3+ ions.

Impact of water on the melting temperature of urea + choline chloride deep eutectic solvent

Abstract: Deep eutectic mixtures are considered as promising green, cheap and easy-to-prepare solvents for applications in catalysis, extraction or material design. In the present work we focus on the urea:choline chloride system. Our aim was to establish its phase diagram and to quantify the impact of naturally present water on the melting temperature for this highly hygroscopic system. The phase diagram of dried urea:choline chloride was established using three complementary apparatuses: a thermostated bath, an optical microscope and a differential scanning calorimeter. Due to limited thermal stability, only mixtures with urea mole fractions between 0.50 and 0.80 were studied. The eutectic point was found for a urea mole fraction of 0.67 at 25 °C and its enthalpy of melting is 93 J g−1. Water can be easily absorbed from the atmosphere, which decreases the melting temperature of eutectic compositions below room temperature. This is quantified in this paper by a systematic study of the melting temperature of a eutectic mixture containing different quantities of water up to 10 wt%. The presence of water should be taken into account for any physico-chemical characterization as well as for applications of this type of eutectic system.

Synergetic effect of MoS2–RGO doping to enhance the photocatalytic performance of ZnO nanoparticles

Abstract: The sunlight driven photocatalytic activity of semiconductor based nanostructures has attracted widespread attention in recent years for environmental remediation and energy applications. Numerous good semiconductors, including ZnO, have wide bandgaps and are active only under ultraviolet light, which comprises only 5% of sunlight. Several strategies, such as noble metal doping, non-metal doping, etc., have been adapted to make ZnO heterostructures active in the visible light region. One other strategy is to dope ZnO with narrow bandgap semiconductors like MoS2. In addition, co-doping with graphene as a support material can enhance pollutant adsorption and can aid in electron transport, thereby leading to pollutant degradation. In this work, we report our investigations on the synergetic role played by MoS2–RGO doping to enhance the photocatalytic activity of ZnO nanoparticles, and especially to utilize both the UV and visible light regions of the solar spectrum. The ZnO–MoS2–RGO heterostructures, having different levels of doping, were prepared by a facile hydrothermal method and were characterized thoroughly using different spectroscopy and microscopy techniques. The photocatalytic performance was evaluated by studying the degradation of methylene blue, a model dye pollutant, and carbendazim, a colorless hazardous fungicide, under natural sunlight irradiation. The results reveal that doping of ZnO nanoparticles with 1 wt% MoS2–RGO was optimal and possessed the highest photocatalytic activity among all the investigated samples. A possible mechanism is proposed and discussed in detail.

Recent advances in iron complexes as potential anticancer agents

Abstract: The revelation of the anticancer properties of cisplatin has inspired research into metal complexes for the treatment of cancer. Several second and third generation cisplatin analogues were developed with claims of good anticancer properties and reduced side effects. However, the persistence of some side effects and the resistance of cancer cells have tempted scientists to explore new metal complexes as anticancer drugs. Therefore, the approach of rational drug design has been extended to the development of non-platinum anticancer drugs, and a large number of such complexes have been developed. Iron complexes are of interest to inorganic medicinal chemists for the development of anticancer agents. The anticancer potency of iron complexes was first reported in ferrocenium picrate and ferrocenium trichloroacetate salts, and was attributed to their ability to form reactive oxygen species, leading to oxidative DNA damage. This review discusses the advances in iron complexes as anticancer agents. The aspects of the photocytotoxicity, redox activity and multinuclearity of anticancer iron complexes are discussed, in addition to discussing ferrocenyl derivatives and salen complexes. The legacy of nanotechnology and synergism in harnessing the potential of iron complexes is highlighted. Finally, the current challenges and future perspectives of iron complexes as anticancer agents are outlined.

Graphene oxide: a promising carbocatalyst for the regioselective thiocyanation of aromatic amines, phenols, anisols and enolizable ketones by hydrogen peroxide/KSCN in water

Abstract: Graphene oxide (GO), as a heterogeneous carbocatalyst, catalyzes the direct thiocyanation of a variety of arenes including aromatic amines, phenols, anisols and carbonyl compounds that possessing α-hydrogen in the presence of hydrogen peroxide and KSCN in water as a green media. This procedure is chemoselective, avoids the use of precious metals and toxic solvents and has a broad substrate scope. Easy removal from the reaction mixture and recyclability with no loss of activity are the key features of graphene oxide in this catalytic system.

Synthesis and molecular structure of arene ruthenium(II) benzhydrazone complexes: impact of substitution at the chelating ligand and arene moiety on antiproliferative activity

Abstract: A convenient method for the synthesis of ruthenium(II) arene benzhydrazone complexes (1–6) of the general formula [(η6-arene)Ru(L)Cl] (arene-benzene or p-cymene; L-monobasic bidentate substituted indole-3-carboxaldehye benzhydrazone derivatives) has been described. The complexes have been fully characterized via elemental analysis, IR, UV-vis, NMR and ESI-MS spectral methods. The solid-state molecular structures of the representative complexes were determined using a single-crystal X-ray diffraction study and the results indicated the presence of a pseudo octahedral (piano stool) geometry. All the complexes were thoroughly screened for their cytotoxicity against human cervical cancer cells (HeLa), human breast cancer cell line (MDA-MB-231) and human liver carcinoma cells (Hep G2) under in vitro conditions. Interestingly, the cytotoxic activity of complexes 3, 4 and 6 is much more potent than cis-platin with low IC50 values against all the cancer cell lines tested. Furthermore, the mode of cell death in the MDA-MB-231 cells was assessed via AO–EB staining, Hoechst 33258 staining, flow cytometry and comet assay. Furthermore, the results of Western blot analyses suggest that complexes 3 and 6 accumulate preferentially in the mitochondria of MDA-MB-231 cells and induce apoptosis via mitochondrial pathways by up-regulating p53 and Bax, and down-regulating Bcl-2.

Biosynthesis, characterization and catalytic activity of an Ag/zeolite nanocomposite for base- and ligand-free oxidative hydroxylation of phenylboronic acid and reduction of a variety of dyes at room temperature

Abstract: This paper reports on the synthesis and use of an Ag/zeolite nanocomposite as a separable catalyst for the ligand-free hydroxylation of phenylboronic acid to phenol and the reduction of 4-nitrophenol (4-NP), methyl orange (MO), congo red (CR), methylene blue (MB) and rhodamine B (RhB) at room temperature. The Ag/zeolite nanocomposite was prepared using the extract of a leaf of Euphorbia prolifera and characterized by FT-IR, XRD, FE-SEM, EDS and TEM analyses. The catalyst was quantitatively recovered and reused without significant loss in the catalytic activity.

Zeolitic imidazole framework-67 as an efficient heterogeneous catalyst for the conversion of CO2 to cyclic carbonates

Abstract: Zeolitic imidazole framework (ZIF)-67 is an efficient heterogeneous catalyst for the cycloaddition of carbon dioxide to epoxides to afford cyclic carbonates. In this work, ZIF-67 was synthesized by a simple and straightforward method at room temperature. The coupling reaction in the presence of ZIF-67 without any co-catalyst or solvent was studied under different conditions. The reaction conversion was more than 99% and the selectivity toward chloropropene carbonate was considerably higher (>99%) than the previously reported ZIF-8. Moreover, the ZIF-67 catalyst could be recycled at least four times without noticeable loss of catalytic activity.

Design and construction of the sandwich-like Z-scheme multicomponent CdS/Ag/Bi2MoO6 heterostructure with enhanced photocatalytic performance in RhB photodegradation

Abstract: A sandwich-like Z-scheme tricomponent CdS/Ag/Bi2MoO6 photocatalytic system was rationally designed and successfully fabricated, in which Ag was loaded onto Bi2MoO6 microspheres by a facile photoreduction method and CdS was subsequently deposited onto the surface of Bi2MoO6 and Ag/Bi2MoO6 through a deposition–precipitation method. During this process, a series of Ag/Bi2MoO6 and CdS/Bi2MoO6 were also prepared. All the composites were characterized by XRD, TEM, SEM, EDX, XPS, UV-vis DRS, and IR spectra to confirm the successful integration of Ag or (and) CdS with Bi2MoO6, the alteration of morphology and the formation of a new phase before and after Ag or (and) CdS loading. The degradation of rhodamine B (RhB) dye under visible light irradiation (>420 nm) revealed that the CdS/Ag/Bi2MoO6 composite exhibited a highly visible-light-responsive photocatalytic performance compared to single Bi2MoO6 or CdS and dual Ag/Bi2MoO6 or CdS/Bi2MoO6. The enhanced photocatalytic performance of CdS/Ag/Bi2MoO6 was ascribed to its special structure – a typical Z-scheme photocatalytic system, in which Ag nanoparticles directly connected to the surface of CdS and Bi2MoO6 to form a solid–solid interface (ohmic contact), acting as a conductor that greatly shortened the distance for photogenerated electron transfer and combined photogenerated electrons from the CB of Bi2MoO6 with the photogenerated holes from the VB of CdS through ohmic contact, and thereby led to the efficient separation of photogenerated electrons and holes and showed stable and strong reducibility and oxidizability. Moreover, the surface plasmon resonance effect of metallic Ag nanoparticles also played an important role in the enhanced photocatalytic performance of RhB degradation under visible light irradiation. Furthermore, investigations on photoluminescence and photoelectrochemical properties also demonstrated indirectly the highly efficient separation of photogenerated electrons and holes in the Z-scheme CdS/Ag/Bi2MoO6 photocatalytic system. This new Z-scheme photocatalytic system will be applied to more photoreactions in further exploration.

A thermally activated manganese 1,4-benzenedicarboxylate metal organic framework with high anodic capability for Li-ion batteries

Abstract: Metal organic frameworks (MOFs) with considerable structural versatility are considered to be potential materials for energy storage. In this work, a Mn-1,4-benzenedicarboxylate (Mn-1,4-BDC) MOF was synthesized by reaction of 1,4-benzenedicarboxylic acid (1,4-BDC) with manganese(II) chloride (MnCl2) using a solvothermal method. When applied as an anode for lithium-ion batteries, the activated Mn-1,4-BDC@200 electrode delivered a high reversible lithium storage capacity of 974 mA h g−1 after 100 cycles at a current density of 100 mA g−1, exhibiting one of the best lithium storage properties among the reported metal organic frameworks (MOFs), also known as coordination polymer (CP) anodes. The excellent electrochemical performance of the Mn-1,4-BDC electrode is also comparable with those reported for Mn2O3 and Mn3O4 nanostructures calcined from Mn-based MOF templates.

Facile synthesis of Ag/ZnO micro-flowers and their improved ultraviolet and visible light photocatalytic activity

Abstract: Three-dimensional (3D) flower-like Ag/ZnO heterostructures with different Ag content were prepared using a facile two-step method. The samples structure, morphology and optical properties were well-characterized using XRD, SEM, EDS, XPS, DRS, PL and ICP-AES techniques. The results demonstrated the successful deposition of Ag nanoparticles on a flower-like ZnO surface. The photocatalytic performance was evaluated by the photocatalytic degradation of rhodamine B (RhB) under ultraviolet and visible light. The results showed that the Ag/ZnO heterostructures had superior photocatalytic activity compared to the pure ZnO samples and the commercial photocatalyst TiO2 (Degussa, P25). The enhanced photocatalytic activity was attributed to the effective separation of electron/hole pairs on flower-like ZnO by employing Ag nanoparticles as a conductor. Furthermore, 3D flower-like Ag/ZnO microspheres exhibited good recycling stabilities over several separation cycles photodegradation.

Nine self-assembled nickel(II)–lanthanide(III) heterometallic complexes constructed from a Salamo-type bisoxime and bearing a N- or O-donor auxiliary ligand: syntheses, structures and magnetic properties

Abstract: Through the self-assembly of a Salamo-type ligand H2L (H2L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane) with Ni(OAc)2·4H2O, Ln(NO3)3·6H2O (Ln(III) = La(III), Gd(III), Tb(III) and Dy(III)) and Py (Py = pyridine) or 4,4′-bipy (4,4′-bipy = 4,4′-bipyridine) or H2bdc (H2bdc = terephthalic acid), nine new Ni(II)–Ln(III) heterometallic complexes [Ni(L)La(OAc)(NO3)2(Py)(CH3OH)]·CH3OH (1), [Ni(L)Dy(OAc)(NO3)2(Py)] (2), 1∞[Ni(L)La(NO3)3(4,4′-bipy)(CH3OH)] (3), 1∞[Ni(L)Tb(NO3)3(4,4′-bipy)] (4), [Ni(L)Dy(OAc)(NO3)2(4,4′-bipy)] (5), [{Ni(L)Ln(NO3)2(DMF)(CH3OH)}2(bdc)] (Ln = La (6) and Gd (7)) and [{Ni(L)Ln(NO3)2(DMF)}2(bdc)] (Ln = Tb (8) and Dy (9)) were obtained, respectively. The acetato ligand bridges the Ni(II) and Ln(III) (Ln = La (1) and Dy (2)) atoms in a μ2 fashion and the Py coordinates to the apical position by a nitrogen atom in the heterobimetallic complexes 1 and 2. Complexes 3 and 4 are 1D coordination polymers constructed from heterobimetallic [Ni(L)Ln] (Ln = La (3) and Tb (4)) units which are connected by the exo-dentate ligand 4,4′-bipy bearing nitrogen-donor atoms, but complex 5 is a heterobimetallic Ni(II)–Dy(III) complex which is prepared under the same reaction conditions as complexes 3 and 4. Four heterotetranuclear dimers were constructed from heterobimetallic [Ni(L)Ln] (Ln = La (6), Gd (7)), Tb (8) and Dy (9) units which are connected by the exo-dentate H2bdc ligand with oxygen-donor atoms. Magnetic measurements were performed on the Gd(III), Tb(III) and Dy(III) complexes.

Silicon carbide foam as a porous support platform for catalytic applications

Abstract: This review provides an overview of the use of foam-structured SiC as a porous support platform in some typical catalytic processes both for gas-phase and liquid-phase reactions, such as H2S selective oxidation, Friedel–Crafts benzoylation and Fischer–Tropsch synthesis, where traditional catalysts have shown their weaknesses. The macroscopic thermally conductive SiC material could be efficiently employed as a support for controlling the active phase, i.e. metal and zeolite, and anchoring the powder-foam nanocarbons in the field of catalysis. In light of the results, one can state that silicon carbide foam could be regarded as an ideal alternative support, which provides a great enhancement of both the catalytic performance and the catalytic stability compared to that of the traditional catalysts, in several gas- and liquid-phase catalytic processes.

Selective glucose conversion to 5-hydroxymethylfurfural (5-HMF) instead of levulinic acid with MIL-101Cr MOF-derivatives

Abstract: The catalytic conversion of glucose to 5-hydroxymethylfurfural (5-HMF) is highly desirable, but the 5-HMF yield obtained using heterogeneous catalysts is still low compared to homogeneous catalysts, and the mechanism is not elucidated completely. In addition, the isolation and purification of 5-HMF still present a challenge as degradation reactions take place and side products form. The formation of 5-HMF from glucose has been reported using several solid acid catalysts; still metal–organic framework (MOF) catalysts could, so far, catalyze the cascade reaction of glucose to 5-HMF only in low yields of less than 16%. Glucose conversion using MOFs is little investigated and here sulfonated MIL-101Cr (MIL-SO3H) was found to achieve 29% conversion of glucose to 5-HMF after 24 h in a THF : H2O (v : v 39 : 1) mixture. The conversion of maltose resulted in 50% 5-HMF yield (saccharide solutions were 5 wt%). When the reaction was carried out in pure THF using MIL catalysts no product was formed, revealing the indispensability of water for the glucose-to-5-HMF conversion. Importantly, MIL-SO3H preferentially leads to 5-HMF over levulinic acid (molar ratio 1 : 0.3), while the catalysts Amberlyst-15 and sulfuric acid form mostly levulinic acid in 5-HMF to levulinic acids ratios of 1 : 3 and 1 : 10, respectively. At the same time, MIL-NO2 is the most selective, yielding only 5-HMF and showing no formation of levulinic acid. Using 5-HMF as a substrate did not result in any conversion to levulinic acid in the presence of MIL-SO3H, thereby ruling out the catalytic formation of levulinic acid from 5-HMF. Catalyst recycle experiments showed that MIL-SO3H stays porous and crystalline, but becomes deactivated through fouling by humin formation. With the use of ethanol as an alternative reaction medium, the formation of insoluble humins could be prevented, but the yield of 5-HMF and 5-ethyl-HMF decreased.

Structured catalysts for dry reforming of methane

Abstract: A major scientific challenge in the recent epoch has been to develop practical processes that can convert greenhouse gases (CO2, CH4) into value added commodity chemicals or fuels. Dry (CO2) reforming of methane (DRM) can be considered as an excellent option in this regard. DRM often requires heterogeneous catalysts such as supported noble metals to efficiently convert CH4 and CO2 into synthesis gas (CO + H2) which is extensively used in numerous industrial processes. Nickel based catalysts are considered as excellent low cost alternatives. However, these catalysts undergo severe deactivation due to sintering of the active phase and/or coke (carbon) deposition on the surface. Significant control over the catalyst sintering along with enhanced coke resistance can be achieved if well defined structures (perovskites, spinels, etc.) are used as catalyst precursors or catalysts. Also, well controlled structured catalysts can be obtained by embedding the active phase into the pore channels of mesostructured materials (typically silica). This review is an attempt to summarize the recent progress in designing structured catalysts for the dry reforming of methane. Merits and demerits of these materials as provided by various authors will be discussed. It is believed that such a single platform will aid the scientific community to understand what is lacking for the fruitful development of sintering free, coke resistant catalysts to convert hydrocarbons into chemical feedstock by consuming these two hazardous greenhouse gases.

Nano-zirconia as an excellent nano support for immobilization of sulfonic acid: a new, efficient and highly recyclable heterogeneous solid acid nanocatalyst for multicomponent reactions

Abstract: Nano-zirconia-supported sulfonic acid [nano-ZrO2-SO3H (n-ZrSA)] is synthesized by immobilizing sulfonic acid groups on the surface of nano zirconium dioxide to produce a novel heterogeneous reusable solid acid nanocatalyst. This new nanocatalyst is characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), the Hammett acidity function and pH analysis. The introduced nano-zirconia-supported sulfonic acid is used as an efficient and recyclable catalyst for different heterocyclic multicomponent reactions such as the synthesis of hexahydroquinoline, 1,8-dioxo-decahydroacridine, polyhydroquinoline and 1,8-dioxo-octahydroxanthene derivatives. Optimization of the reaction conditions was studied using a central composite design (CCD) which is one of the most widely used response surface methodologies. The newly prepared heterogeneous solid acid nanocatalyst is easily separated and reusable for five cycles without any apparent loss of its catalytic activity, which confirmed the stability of the covalent bonding of the sulfonic acid groups. n-ZrSA has advantages such as its low cost, low toxicity, ease of preparation, good stability, high reusability and operational simplicity.

Multiscale adsorption and transport in hierarchical porous materials

Abstract: This review presents the state-of-the-art of multiscale adsorption and transport in hierarchical porous materials, i.e. solids combining different porosity scales (from nm to > μm). Adsorption and desorption phenomena that can be observed in ordered and disordered porous materials are first discussed (including a discussion of the effect of pore size/confinement on the critical behavior of confined fluids). The general behavior of adsorption in hierarchical porous materials is then presented with a special emphasis on characterization techniques to probe the morphology (pore disorder) and topology (connectivity) of the pore network. As for transport, after a presentation of the different diffusion mechanisms that can be observed in porous solids depending on the pore scale, a brief discussion of the theoretical frameworks available to describe multiscale transport is provided. The results obtained for transport in hierarchical porous solids are then reviewed together with some upscaling strategies that can be used to build a bottom-up description of multiscale transport in hierarchical porous media.

DFT investigation of Ni-doped graphene: catalytic ability to CO oxidation

Abstract: Herein, CO oxidation on Ni-doped graphene (Ni-Gr) is investigated by first-principle calculations. The strong binding energy (−7.57 eV) of the Ni atom at a single vacancy in graphene and high energy barrier (3.41 eV) for Ni atom mobility in graphene suggest that graphene is stable even after Ni doping, which avoids the problem of metal clustering. The stronger binding interaction between Ni-Gr and O2 than that between Ni-Gr and CO can prevent CO poisoning to Ni-Gr. To explore the catalytic effect of CO oxidation on Ni-Gr, both the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms are investigated. The overall energy barrier at 0 K for the LH and ER mechanisms is 0.63 and 0.77 eV, respectively. At 298.15 K, the overall energy barrier for the LH mechanism decreases to 0.58 eV, whereas that for the ER mechanism increases to 0.88 eV, which implies that CO oxidation on Ni-Gr prefers to proceed via the LH mechanism kinetically. Our results show that the studied system, Ni-Gr, has chemical stability against metal clustering and CO poisoning, and it is a promising catalyst for CO oxidation at mild temperatures. This study provides a good theoretical guideline for the development of Ni-Gr based CO oxidation catalysts.

Ln3+ post-functionalized metal–organic frameworks for color tunable emission and highly sensitive sensing of toxic anions and small molecules

Abstract: A facile strategy was put forward to fabricate highly luminescent metal–organic frameworks (MOFs) with tunable and white-light emission by incorporating lanthanide cations (Ln3+) into the channels of MIL-121 (Al(OH)(H2btec)·H2O) whose uncoordinated carboxyl groups can act as post-synthetic modification sites. The intense luminescence of Ln3+ doped MIL-121 indicates that the framework with rigid, permanently porous structure and non-coordinated carboxyl can serve as both a scaffold and an antenna for hosting and sensitizing the luminescence of Ln3+ cations. Moreover, a fine-tuning of the emitted color luminescence can be easily achieved by simply modulating the doping ratio or adjusting the excitation wavelength. Notably, the red–green–blue-based white light emitting Ln-MOFs can be realized by simultaneously doping Eu3+ and Tb3+ into the host framework. In addition, because of the excellent luminescence and the structural stability of Ln3+ functionalized MIL-121 (Ln3+@MIL-121) in water or solvents, the Eu3+@MIL-121 was developed as a luminescent probe for sensing of anions in aqueous solutions and small organic molecules. Luminescent studies reveal that Eu3+@MIL-121 not only display a high-sensitivity sensing function with respect to fluoride and dichromate ions but also exhibit significant solvent-dependent luminescent response to small-molecule pollutants, such as chloroform and acetone.

The first report on the preparation of boehmite silica sulfuric acid and its applications in some multicomponent organic reactions

Abstract: Boehmite silica sulfuric acid (boehmite-SSA) has been prepared for the first time via an efficient sequential synthetic procedure. Initially, boehmite nanoparticles were prepared, coated by silica, and then reacted with chlorosulfonic acid to obtain boehmite-SSA. A simple, inexpensive, environmentally friendly and efficient procedure for the synthesis of polyhydroquinoline and 2,3-dihydroquinazolin-4(1H)-one derivatives using this compound as an efficient and novel nanocatalyst has been described. Boehmite-SSA is a stable, heterogeneous, cost-effective, easy to handle, and recoverable catalyst and can be reused for several consecutive runs without a significant loss of catalytic activity. Its structure was characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Hydrothermal formation of graphene aerogel for oil sorption: the role of reducing agent, reaction time and temperature

Abstract: Graphene aerogels (GAs) are widely studied in the oil contamination field in recent years. Among the preparation approaches, hydrothermal treatment employing a certain reducing agent has attracted much attention owing to the environmentally friendly and facile synthesis process. In this work, we systematically investigate the effects of various reducing agents including ammonia, ethanediamine (EDA) and vitamin C (VC) at different hydrothermal temperatures (80, 100, 120, 140, 160 and 180 °C) and reaction times (4, 8, 12, 16, 20 and 24 h) on the density, specific surface area (SSA), strength, morphology and adsorption performance of GAs. The results reveal that GAs reduced by VC possess the most outstanding performance for mechanical strength and re-utilization but have poor adsorption capacity (Qwt), whereas the sample obtained with ammonia exhibits the highest Qwt for both lube (160 g g−1) and n-hexane (105 g g−1). However, this sample not only reveals the worst mechanical strength which leads to a sharp decrease of the Qwt during the adsorption–squeezing experiments, but GA reduced by ammonia is also very sensitive to the reaction time and temperature. Therefore, EDA is a very promising reducing agent for the hydrothermal process as the resulting GA can maintain a high Qwt and reveals a wide hydrothermal preparation window.

The removal of organophosphorus pesticides from water using a new amino-substituted calixarene-based magnetic sporopollenin

Abstract: This study describes the synthesis, characterization and application of a new amino-substituted p-tert-butylcalix[4]arene-based magnetic sporopollenin, Calix-EPPTMS-MS (4), for the removal of two toxic organophosphorus pesticides, namely chlorpyrifos and diazinon, from contaminated water. The synthesized Calix-EPPTMS-MS (4) was characterized using FT-IR spectroscopy, a UV-Vis spectrophotometer, an elemental analyzer, scanning electron microscopy and energy dispersive spectroscopy. The pesticide removal efficiency of Calix-EPPTMS-MS (4) was evaluated through a batch-wise method and gas chromatography using a micro-electron capture detector (GC-μECD). Experimental parameterssuch as adsorbent dosage, pesticide concentration, solution pH and contact time were optimized. Excellent removal efficiencies of 96% for chlorpyrifos and 88% for diazinon were achieved at pH 7 within 10 min of contact time. Kinetic studies showed that both pesticides followed the pseudo-second-order rate model with a coefficient of determination (R2) of 0.999. The Langmuir and Dubinin–Radushkevich isotherms with high values of R2 revealed that chlorpyrifos and diazinon adsorption on the Calix-EPPTMS-MS (4) adsorbent follows the chemisorption mechanism. Pesticide contaminated wastewater samples were used to assess the field applicability of the Calix-EPPTMS-MS (4) adsorbent. The results obtained showed that the newly fabricated adsorbent material Calix-EPPTMS-MS (4) is an efficient adsorbent and exhibits great potential as an alternative adsorbent for pesticide removal.

One-pot, efficient and green synthesis of acridinedione derivatives using highly monodisperse platinum nanoparticles supported with reduced graphene oxide

Abstract: An efficient, high yielding, quick method has been developed for the synthesis of acridinedione derivatives via a one-pot, multi-component condensation of dimedone (1), various aromatic aldehydes (2a–i), and various aromatic amines (3a,b) using highly monodisperse platinum nanoparticles supported with reduced graphene oxide (Pt NPs@rGO) as a recyclable heterogeneous catalyst. This method takes advantage of the fact that water/ethanol (a green solvent) is used in combination with Pt NPs@rGO nanoparticles as a catalyst which can be easily recovered and reused for further runs. This highly monodisperse catalyst has been used for the first time as a highly stable, exceptionally reusable, isolable, bottleable, long-lived and highly efficient catalyst for the synthesis of acridinedione derivatives from dimedone, aromatic aldehydes and various amines with great catalytic performance. The synthesized catalyst was characterized using transmission electron microscopy, high resolution electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopy techniques. The results of these analyses show the formation of highly crystalline and colloidally stable highly monodisperse Pt NPs@rGO. This highly monodisperse catalyst is a most efficient catalyst which gives the high yield of products in a short time.

Kinetics of nitrogen-doped carbon dot formation via hydrothermal synthesis

Abstract: Carbon dots (CDs) have attracted great attention because of their unique luminescence properties, chemical inertness, thermal stability, high water solubility, low toxicity, and ease of functionalization. Here, the kinetics of nitrogen-doped CD (N-CD) formation by hydrothermal synthesis were evaluated in an attempt to realize the rapid and efficient production of N-CDs. A series of N-CDs was synthesized using various heating rates, reaction times, reaction temperatures, and precursor concentrations. Characterization of the series of N-CDs indicated that N-CD formation is a first-order reaction with a reaction rate constant of 0.634 min−1. In addition, systematic investigation revealed that synthesis temperature is a more important factor to obtain highly fluorescent N-CDs than reaction time. Citric acid amides are formed by the reaction between citric acid and urea at 130 °C and N-CDs consisting of two or three citric acid amide molecules are formed through dehydration, deammoniation and dehydrogenation of citric acid at 150 °C. By adjusting the operating conditions, N-CDs with a highest quantum yield of 39.7% could be produced at a production rate of 50 g h−1 with a reaction time of 16 min. The N-CDs were then embedded in polyvinyl alcohol (PVA) nanofibers. The luminescence intensity of the N-CD–PVA composite nanofibers was more than twice that of the N-CDs in solution.

A rapid, facile and green synthesis of Ag@AgCl nanoparticles for the effective reduction of 2,4-dinitrophenyl hydrazine

Abstract: In this study, we have developed a green and single-step process for the fabrication of Ag@AgCl nanoparticles (NPs) using the leaf extract of Momordica charantia. This method does not require the utilization of any surfactant/halide source or external energy. The uniqueness of the developed method lies in its fast synthesis rates (1 min for Ag@AgCl NPs). The phytochemicals present in the leaf extract act as a reducing as well as stabilizing agent and are responsible for the formation of Ag@AgCl NPs. The synthesized Ag@AgCl NPs exhibited a catalytic activity for the reduction of 2,4-dinitrophenyl hydrazine (DNPH). It followed the pseudo-first order reaction and the rate constant (k) for the reduction of 2,4-DNPH was found to be 5.2 × 10−2 min−1. For the first time, the reduction of 2,4-dinitrophenyl hydrazine was reported using Ag@AgCl nanoparticles as a catalyst.