Showing papers by "Asim Bhaumik published in 2015"

Mesoporous materials: versatile supports in heterogeneous catalysis for liquid phase catalytic transformations

Abstract: Due to their unprecedented intrinsic structural features, like tunable pore diameter of nanoscale dimensions, huge BET surface areas and good flexibility to recognize/accommodate various functional groups and metals onto the surface, an inevitable linkage of nanoporous materials with catalysis has been built-up over the past few decades. As a result of which, a huge number of communications and articles dealing with these materials with nanoscale porosity have come to light. In this review, our objective is to provide a comprehensive overview of mesoporous solids, the most remarkable member of the nanoporous family of materials, the general strategy for their syntheses and application of functionalized porous materials in liquid phase catalytic reactions. In the latter part, the role of catalytic centres in various organic transformations over these functionalized mesoporous materials and their economical, environmental and industrial aspects are described in detail.

Sulfonated Porous Polymeric Nanofibers as an Efficient Solid Acid Catalyst for the Production of 5‐Hydroxymethylfurfural from Biomass

Abstract: Sustainable supply of energy is one of the biggest challenges today. The conversion of energy from any abundant and renewable resources would be an ideal solution for this ever increasing demand of sustainable energy. Biomass provides a potential energy alternative through the platform chemical 5-hydroxymethylfurfural (HMF), which is considered as a sustainable source for liquid fuels and commodity chemicals. Herein, we report the synthesis of a nanoporous polytriphenylamine (PPTPA-1) having high surface area (1437 m2 g−1) by a simple one-step oxidative polymerization pathway. Upon sulfonation of PPTPA-1, the sulfonated polymer SPPTPA-1 showed very high surface acidity and it has been successfully employed as a solid acid catalyst for direct conversion of sugar to HMF. Both PPTPA-1 and SPPTPA-1 materials have distinct nanofiber morphologies and they are characterized thoroughly by using powder XRD, FTIR spectroscopy, 13C solid state magic-angle-spinning NMR spectrometry, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and N2 sorption techniques. We have optimized the HMF yields by using different carbohydrate sources and estimated the recycling efficiency of the catalyst.

Green synthesis of Pt-doped TiO2 nanocrystals with exposed (001) facets and mesoscopic void space for photo-splitting of water under solar irradiation.

Abstract: We report a non-trivial facile chemical approach using ionic liquid ([bmim][Cl]) as a porogen for the synthesis of (001) faceted TiO2 nanocrystals having mesoscopic void space. This faceted TiO2 nanomaterial has been doped with Pt nanoclusters through chemical impregnation. The resulting Pt-doped TiO2 nanomaterials are thoroughly characterized by powder X-ray diffraction (PXRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), ultra high resolution transmission electron microscopy (UHR-TEM), energy dispersive X-ray spectrometry (EDX), UV-vis diffuse reflection spectroscopy (DRS) and N2 sorption studies. These Pt/TiO2 nanocrystals with (001) exposed facets are employed as efficient and benign catalysts for hydrogen production from pure water and methanol–water systems under one AM 1.5G sunlight illumination. The effect of platinum loading and methanol–water ratio on the photocatalytic activity of the faceted TiO2 nanocrystals are investigated and it is found that hydrogen evolution rates have been enhanced significantly upon Pt loading. Under optimized reaction conditions the highest photocatalytic activity of 11.2 mmol h−1 g−1 has been achieved over ca. 1.0 wt% Pt loaded Pt/TiO2 nanocrystals with (001) exposed facets, which is one of the highest hydrogen evolution rates over the noble metal/TiO2 system reported to date in the literature.

Fabrication of Ruthenium Nanoparticles in Porous Organic Polymers: Towards Advanced Heterogeneous Catalytic Nanoreactors.

Abstract: A novel strategy has been adopted for the construction of a copolymer of benzene-benzylamine-1 (BBA-1), which is a porous organic polymer (POP) with a high BET surface area, through Friedel-Crafts alkylation of benzylamine and benzene by using formaldehyde dimethyl acetal as a cross-linker and anhydrous FeCl3 as a promoter. Ruthenium nanoparticles (Ru NPs) were successfully distributed in the interior cavities of polymers through NaBH4, ethylene glycol, and hydrothermal reduction routes, which delivered Ru-A, Ru-B, and Ru-C materials, respectively, and avoided aggregation of metal NPs. Homogeneous dispersion, the nanoconfinement effect of the polymer, and the oxidation state of Ru NPs were verified by employing TEM, energy-dispersive X-ray spectroscopy mapping, cross polarization magic-angle spinning (13)C NMR spectroscopy, and X-ray photoelectron spectroscopy analytical tools. These three new Ru-based POP materials exhibited excellent catalytic performance in the hydrogenation of nitroarenes at RT (with a reaction time of only ≈ 30 min), with high conversion, selectivity, stability, and recyclability for several catalytic cycles, compared with other traditional materials, such as Ru@C, Ru@SiO2, and Ru@TiO2, but no clear agglomeration or loss of catalytic activity was observed. The high catalytic performance of the ruthenium-based POP materials is due to the synergetic effect of nanoconfinement and electron donation offered by the 3D POP network. DFT calculations showed that hydrogenation of nitrobenzene over the Ru (0001) catalyst surface through a direct reaction pathway is more favorable than that through an indirect reaction pathway.

A triazine-based porous organic polymer: a novel heterogeneous basic organocatalyst for facile one-pot synthesis of 2-amino-4H-chromenes

Abstract: A new triazine-based porous organic polymer TPOP-2 has been synthesized through the reaction between cyanuric chloride and tris(2-aminoethyl)amine in anhydrous 1,4-dioxane under N2 atmosphere. The porous polymer has been characterized by powder X-ray diffraction, N2 sorption, HR TEM, FE SEM, 13C CPMAS NMR, CO2-TPD, TG-DTA and FT IR spectroscopic tools. Due to the high density of amine and triazine functional groups, this porous polymer is N-rich and possesses excellent surface basicity, and is utilized as a heterogeneous metal-free basic organocatalyst for the one-pot three-component condensation reaction of aromatic aldehyde, activated phenols (resorcinol and 2-naphthol) and malononitrile for the synthesis of 2-amino-chromenes under solvent-free or aqueous conditions. The ease of catalyst synthesis and its efficient use for five consecutive cycles without noticeable loss in catalytic activity suggest significant future potential of this new N-rich porous organic polymer material for a wide range of base catalyzed reactions.

Pyrene-Based Porous Organic Polymers as Efficient Catalytic Support for the Synthesis of Biodiesels at Room Temperature

Abstract: New pyrene-based microporous organic polymers PPOP-1, PPOP-2, and PPOP-3 have been synthesized via Friedel–Crafts alkylation reaction between pyrene and bis(1,4-dibromomethyl)benzene at their different molar ratios in the presence of a Lewis acid catalyst FeCl3 under refluxing conditions. Pore surfaces of PPOP-1, PPOP-2, and PPOP-3 have been functionalized by −SO3H groups via chlorosulfonic acid treatment under controlled reaction conditions to obtain sulfonated porous organic polymers, and these are designated as SPPOP-1, SPPOP-2, and SPPOP-3, respectively. Powder X-ray diffraction, N2 sorption, HR-TEM, FE-SEM, NH3-TPD, solid state 13C CP MAS-NMR, and FT-IR spectroscopic tools are employed to characterize these materials. These sulfonated porous polymers showed nanofiber-like or spherical morphology, very high surface acidity, and excellent catalytic activity for the synthesis of biodiesels via esterification/transesterification of long chain fatty acids/esters at room temperature together with very high...

Mesoporous BaTiO3@SBA-15 derived via solid state reaction and its excellent adsorption efficiency for the removal of hexavalent chromium from water

Abstract: We report the synthesis of a barium-titanate/mesoporous silica nanocomposite material BaTiO3@SBA-15 via aerosol assisted solid state reaction using SBA-15 as a hard template. Hexavalent chromium is one of the most harmful contaminants of industrial waste-water. We have used BaTiO3@SBA-15 nanocomposite as an adsorbent for the removal of chromium(VI)-contaminated water and it showed an adsorption capacity of 98.2 wt% within only 40 min contact time in a batch reactor. This mesoporous composite has retained this excellent adsorption efficiency of hexavalent chromium for several repetitive cycles, suggesting its future potential for the remediation of water contaminated with Cr(VI).

A highly efficient non-enzymatic glucose biosensor based on a nanostructured NiTiO3/NiO material

Abstract: An efficient and novel non-enzymatic glucose sensing platform composed of self-assembled crystalline NiTiO3/NiO nanoparticles is reported in this article. The mixed oxide nanoparticles have been synthesized using a facile sol–gel method mediated by evaporation induced self-assembly (EISA) in non-aqueous media. After annealing at 673 K the final product obtained was well characterized using various analytical tools like powder X-ray diffraction (PXRD) and scanning and transmission electron microscopy (SEM and TEM), along with energy dispersive X-ray spectroscopy (EDS)and UV-visible diffuse reflectance spectroscopy (DRS) studies which reveal that the nanomaterial is composed of ca. 30–35 nm sized nanocrystals that have an ilmenite NiTiO3 structural phase with some percentage of bunsenite NiO. The NiTiO3/NiO nanoparticles exhibit an outstanding electro-catalytic activity towards glucose oxidation in 0.1 M NaOH alkaline media at an applied potential of +0.55 V (vs. Ag/AgCl electrode). The glucose sensing investigation of this Ni–Ti electrode indicates a very high sensitivity and a low limit of detection (LOD) of 1454 μA mM−1 cm−2 and 0.06 μM, respectively. The glucose level in human blood serum was also tested with our sample which produced a satisfactory result. Thus, the NiTiO3/NiO electrode can be used as a highly effective, economical, stable and non-air sensitive platform for non-enzymatic glucose detection.

Mesoporous Titania-Iron(III) Oxide with Nanoscale Porosity and High Catalytic Activity for the Synthesis of β-Amino Alcohols and Benzimidazole Derivatives

Abstract: A mesoporous TiO2-Fe2O3 mixed oxide material (MTF-1E) with nanoscale porosity and a high BET surface area was synthesized using sodium dodecyl sulfate (SDS) as a structure-directing agent. The material was characterized by powder XRD, high-resolution TEM, N2 sorption, and NH3 temperature-programmed desorption studies. The catalyst shows an excellent regioselectivity for the ring-opening of epoxides with amines under solvent-free conditions at room temperature for the synthesis of a series of β-amino alcohols. It also showed a very high catalytic efficiency for the synthesis of benzimidazole derivatives in water. The catalyst can be recovered easily from the reaction medium and reused six times without a significant decrease in its catalytic activity and selectivity.

Tailored Synthesis of Porous TiO2 Nanocubes and Nanoparallelepipeds with Exposed {111} Facets and Mesoscopic Void Space: A Superior Candidate for Efficient Dye-Sensitized Solar Cells

Abstract: Anatase TiO2 nanocubes and nanoparallelepipeds, with highly reactive {111} facets exposed, were developed for the first time through a modified one pot hydrothermal method, through the hydrolysis of tetrabutyltitanate in the presence of oleylamine as the morphology-controlling capping-agent and using ammonia/hydrofluoric acid for stabilizing the {111} faceted surfaces. These nanocubes/nanoparallelepipeds were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and high angle annular dark-field scanning TEM (HAADF-STEM). Accordingly, a possible growth mechanism for the nanostructures is elucidated. The morphology, surface area and the pore size distribution of the TiO2 nanostructures can be tuned simply by altering the HF and ammonia dosage in the precursor solution. More importantly, optimization of the reaction system leads to the assembly of highly crystalline, high surface area, {111} faceted anatase TiO2 nanocubes/n...

Controlled Synthesis of a Hexagonal‐Shaped NiO Nanocatalyst with Highly Reactive Facets {1 1 0} and Its Catalytic Activity

Abstract: A new facile chemical approach has been developed to produce hexagonal-shaped NiO nanocrystals with high-energy facets {1 1 0} under hydrothermal synthesis followed by annealing in the presence of air. The phase purity, crystallinity, shape/size, and mesostructure of NiO nanocrystals were investigated by powder XRD and high-resolution transmission electron microscopy. The size, shape, and exposed crystal facets of the nanocrystals are the key factor for their physical and chemical properties. Herein, the chemical properties of hexagonal-shaped NiO nanocrystals have been tested for the reduction of carbonyl compounds in comparison with NiO nanoparticles and bulk NiO materials. The reactivity of the NiO nanocrystals is enhanced dramatically through morphology evolution. In particular, hexagonal-shaped NiO nanocrystals with highly reactive {1 1 0} facets exhibit approximately 12 and 25 % higher catalytic activity than NiO nanoparticles and bulk NiO, respectively. These hexagonal-shaped NiO nanocrystals are active over several cycles for the reduction of carbonyl compounds to their respective alcohol in the presence of 2-propanol.

Self-assembled sulfated zirconia nanocrystals with mesoscopic void space synthesized via ionic liquid as a porogen and its catalytic activity for the synthesis of biodiesels

Abstract: a b s t r a c t Self-assembled ZrO2 nanocrystals have been synthesized through a facile chemical route via steamassisted ionothermal method using 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) as a porogen. The template-free material has been sulphonated by 1(N) H2SO4 at room temperature followed by calcination in air at 723 K. Both ZrO2 and the sulfonated zirconia materials are thoroughly characterized by powder X-ray diffraction (PXRD), ultra high-resolution transmission electron microscopy (UHR-TEM), Fourier transform infrared spectroscopy (FT-IR), FE-SEM, N2 sorption, and NH3-TPD analyses. The sulfonated material has been employed as efficient and environmentally benign heterogeneous catalyst for the synthesis of biodiesels based on long chain fatty acid esters. The catalyst can be easily recovered and reused at least for five times without significant decrease in its catalytic activity. © 2015 Elsevier B.V. All rights reserved.

Cubic Ag2O nanoparticle incorporated mesoporous silica with large bottle-neck like mesopores for the aerobic oxidative synthesis of disulfide

Abstract: Highly stable, environmentally benign cubic Ag2O nanoparticles dispersed on mesoporous silica with large bottle-neck like mesopores were synthesized and characterized by BET surface area analysis, HR TEM, EDX, FTIR and powder XRD studies. The Ag2O nanoparticles were homogeneously distributed having an average size of 20–40 nm. The activity of the catalyst was probed through an efficient aerobic chemoselective oxidation of thiols to disulfides in water under atmospheric oxygen as the cheapest oxidant. Alkyl, aryl and imine containing symmetrical disulfides can be easily obtained in high yields under mild reaction conditions with no over oxidized product. The efficiency of the catalyst was further demonstrated as the highly sensitive imine bond was well sustained under these mild reaction conditions. Moreover, unlike the other literature precedents, in this present work, single crystal structures of both simple symmetrical disulphide as well as imine containing disulphides are reported for the first time. The catalyst is very much water compatible and can be recycled and reused for at least five cycles. The standard leaching experiment proved that the reaction was heterogeneous with this recyclable catalyst.

Faceted Titania Nanocrystals Doped with Indium Oxide Nanoclusters As a Superior Candidate for Sacrificial Hydrogen Evolution without Any Noble-Metal Cocatalyst under Solar Irradiation

Abstract: Development of unique nanoheterostructures consisting of indium oxide nanoclusters like species doped on the TiO2 nanocrystals surfaces with {101} and {001} exposed facets, resulted in unprecedented sacrificial hydrogen production (5.3 mmol h–1 g–1) from water using methanol as a sacrificial agent, under visible light LED source and AM 1.5G solar simulator (10.3 mmol h–1 g–1), which is the highest H2 production rate ever reported for titania based photocatalysts, without using any noble metal cocatalyst. X-ray photoelectron spectroscopy (XPS) analysis of the nanostructures reveals the presence of Ti–O–In and In–O–In like species on the surface of nanostructures. Electron energy-loss spectroscopy (EELS) elemental mapping and EDX spectroscopy techniques combined with transmission electron microscope evidenced the existence of nanoheterostructures. XPS, EELS, EDX, and HAADF-STEM tools collectively suggest the presence of indium oxide nanoclusters like species on the surface of TiO2 nanostructures. These indi...

Cubic Perovskite ZnTiO3 Nanopowder as a Recyclable Heterogeneous Catalyst for the Synthesis of 1,6-Naphthyridines in Water.

Abstract: Cubic perovskite ZnTiO3 nanopowder has been prepared by means of a sustainable sol-gel method The nanopowder (12-20 nm) has been thoroughly characterized by N2 sorption analysis, high-resolution (HR) TEM, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), SEM, and FTIR analyses The environmentally benign synthesis of highly substituted 1,6-naphthyridines catalyzed by ZnTiO3 nanopowder in aqueous media has been demonstrated It requires two different catalytic functions, that is, an acid one, which is provided by TiIV ions, and a basic one, which is provided by the oxide ion incorporated within the ZnTiO3 metal oxide framework 1,6-Naphthyridines are of tremendous biological importance, and this method is simple and environmentally friendly The greenness of the process was satisfactorily established as water was exploited as the reaction medium and there was very high atom economy

Mesoporous ZnAl2O4: an efficient adsorbent for the removal of arsenic from contaminated water

Abstract: We report, for the first time, an efficient soft-templating strategy for the synthesis of mesoporous ZnAl2O4 using the supramolecular assembly of lauric acid (surfactant) as a template under alkaline pH conditions. A 50 : 50 (v/v) mixture of water–ethanol has been found to be a very efficient synthesis medium for the dissolution of inorganic precursors, retaining the supramolecular assembly of the lauric acid surfactant and adjusting the necessary pH of the synthesis gel, which are very crucial parameters to obtain the stable mesophase of zinc aluminate. This mesoporous ZnAl2O4 material has retained the mesophase upon calcination, showed good BET surface area and electron microscopic results revealed that the material is composed of tiny spherical nanoparticles of dimensions ca. 5–7 nm size. Mesoporous ZnAl2O4 showed very good adsorption efficiency for the removal of arsenic from contaminated water. An efficient synthesis strategy, high BET surface area, stable mesophase and good adsorption efficiency for AsO43− from arsenic-contaminated water by the mesoporous ZnAl2O4 material have huge potential to be explored in the large scale purification of groundwater.

Aerobic Baeyer–Villiger oxidation of cyclic ketones over periodic mesoporous silica Cu/Fe/Ni/Co-HMS-X

Abstract: Baeyer–Villiger oxidation is important reaction in the organic synthesis for designing value added lactone/esters from the respective carbonyl compounds. Usually an active metal-containing material in the presence of peroxides catalyzes this reaction. Here highly ordered metal promoted periodic mesoporous silica with high surface area has been synthesized hydrothermally by the sol–gel method and thoroughly characterized by surface area and porosity measurements, SAXS, FESEM, HRTEM, FTIR, UV–Vis, NH 3 -TPD and XRD techniques. Liquid phase Baeyer–Villiger oxidation of ketones to the corresponding esters have been carried out using molecular oxygen as an oxidant, benzaldehyde as the sacrificing agent over Co-HMS-X and M-Co-HMS-X (metal = Ni, Fe, Cu) as catalysts. The obtained results demonstrate that among the three promoted catalyst, i.e. Ni-Co-HMS-X, Cu-Co-HMS-X and Fe-Co-HMS-X, Ni promoted catalyst is a promising and efficient catalyst with high catalytic activity (>99% cyclohexanone conversion and >99% ɛ-caprolactone selectivity) for the oxidation of cyclohexanone to ɛ-caprolactone. The high catalytic activity is attributed to the Ni on the wall of mesoporous silica along with cyclohexanone, which results in successful completion of the oxygen transfer step and generation of ɛ-caprolactone. Interesting information regarding cooperative role of cobalt and nickel towards catalytic activity is observed.

Bismuth supported SBA-15 catalyst for vapour phase Beckmann rearrangement reaction of cyclohexanone oxime to ɛ-caprolactam

Abstract: Development of environmental benign as well as low cost metal precursor based catalyst is a challenge for chemical industry. In this work we report Bi promoted SBA-15 catalyst for vapour phase Beckmann rearrangement reaction of cyclohexanone oxime. The three different Bi loaded SBA-15 catalysts are prepared and characterized by BET surface area and porosity measurement, small angle X-ray scattering, wide angle X-ray diffraction, field emission scanning electron microscope, high resolution transmission electron microscope, ultraviolet–visible spectroscope, Fourier transform infrared spectroscopy and temperature programmed desorption techniques. Further, catalytic activity is optimized by changing reaction temperature, pre-treatment temperature and pre-treatment time so that 100% cyclohexanone oxime conversion and 100% ɛ-caprolactam selectivity has been achieved. Role of solvent, silylation and time on stream has also been examined. The TPD profiles of all three bismuth loaded samples are mainly characterized by weak acidic sites or surface silanol groups. The FTIR profile shows hydroxyl rich surface in the vicinity of bismuth at Bi-SBA-15 (Bi/Si = 1/100). Based on catalyst characterization and activity data correlation, it can be suggested that protonation at oxime oxygen can be triggered by surface silanol in the vicinity of a Lewis acid centre bismuth. The high space-time-yield of caprolactum was 114.3 mol gcat−1 h−1 was obtained.

Stable room temperature magnetic ordering and excellent catalytic activity of mechanically activated high surface area nanosized Ni0.45Zn0.55Fe2O4

Abstract: Herein we report the structural, microstructural, dc magnetic and hyperfine properties along with catalytic activity of mechanosynthesized nanosized Ni0.45Zn0.55Fe2O4 (∼12 nm). The Rietveld refinement of the powder X-ray diffraction data, high resolution transmission electron microscopy and the infield Mossbauer study suggest that the sample is nanosized pure single phase cubic spinel of Fdm symmetry with good crystallinity and it possesses equilibrium cation distribution ((Fe3+0.45Zn2+0.55)A[Fe3+1.55Ni2+0.45]BO4). The sample exhibits ferrimagnetic ordering with high saturation magnetization (MSAT = 53, 72 and 76 emu g−1 at 300, 100 and 10 K, respectively), coercivity (HC = 280, 1200 and 2800 Oe at 300, 100 and 10 K, respectively), collective magnetic excitations, spin canting and memory effect in dc magnetization. The infield Mossbauer study suggests that the interior region of the particles is perfectly ferrimagnetic in nature, while the spins at the surface region are ferrimagnetically coupled but noncollinearly aligned. Despite its nanometric size, the sample does not show superparamagnetic behavior but rather retains stable magnetic order at room temperature due to enhancement of stress and surface anisotropy energy caused by high energy ball milling. We have shown that the presence of collective magnetic state along with surface spin disorder are the underlying reason for having slow dynamics and memory effect in the sample. Further, the BET (Brunauer–Emmett–Teller) surface area and the pore volume of the sample are 233 m2 g−1 and 0.475 cm3 g−1, respectively. The temperature programmed desorption (TPD) of ammonia suggests that the surface of this porous material is highly acidic (1.516 mmol g−1). Because of its high surface acidity and BET surface area the material acts as an efficient heterogeneous catalyst in the one pot synthesis of 3,4-dihydropyrimidine-2(1H)-ones (DHPMs) by Biginelli condensation reaction. This sample can be used in magnetic data storage devices, coding, storing and retrieving of binary numbers through magnetic field change and also as a very efficient heterogeneous, magnetically separable and recyclable catalyst.

N-rich porous organic polymer with suitable donor–donor–acceptor functionality for the sensing of nucleic acid bases and CO2 storage application

Abstract: A new high surface area porous organic polymer PDVTD-1 (poly-divinylbenzene-co-tartardiamide) has been synthesized via radical copolymerization of divinylbenzene and (+)-N,N′-diallyltartardiamide using AIBN initiator under solvothermal conditions. A detailed characterization of this functionalized porous polymer is performed using N2 sorption, solid state 13C CP MAS NMR, FT-IR and UV-Vis spectroscopy, HR-TEM, FE-SEM, TGA/DTA and CHN analysis. Photoluminescence study of the material is carried out to investigate the sensing behaviour of PDVTD-1 towards different nucleic acid bases. It is observed that at very low concentration of base (i.e. 10−6 to 10−7 M) PDVTD-1 can selectively sense cytosine, whereas in the concentration range 10−3 to 10−5 M adenine, thymine and uracil also shows quenching of its fluorescence intensity. Moreover, this N-rich porous polymer PDVTD-1 showed excellent CO2 uptake capacity of 8.76 mmol g−1 (38.54 wt%) at 273 K and 3 bar pressure with an initial isosteric heat of adsorption (Qst) of 72 kJ mol−1.