Search

In the present work, a one-dimensional metal-organic framework, {[Zn3(TBIB)2(Cl)6]11H2O}n (1), has been synthesized under high temperature and acidic conditions by utilizing the tripodal ligand 1,...

A two-dimensional, tetragonal porous metal organic framework {[Zn2(TBIB)2(HTCPB)2]·9DMF·19H2O}n (1) has been synthesized under hydrothermal conditions by employing 1,3,5-tri(1H-benzo[d]imidazol-1-y...

Biodiesel engines produce several intermediate species, which can potentially harm the human health. The concentration of these species and their health risk potential varies depending on engine technology, fuel, and engine operating condition. In this study, experiments were performed on a large number of engines having different configurations (emissions norms/fuel used), which were operated at part load/full load using B20 (20% v/v biodiesel blended with mineral diesel) and mineral diesel. Experiments included measurement of gaseous emissions, and physical, chemical, and biological characterization of exhaust particulate matter (PM). Chemical characterization of PM was carried out for detecting polycyclic aromatic hydrocarbons (PAH's) and PM bound trace metals. The biological toxicity associated with PM was assessed using human embryonic kidney 293T cells (HEK 293T). The mutagenic potential of the PM was tested at three different concentrations (500, 100, and 50 μg/mL) using two different Salmonella strains, TA98 and TA100, with and without liver S9 metabolic enzyme fraction. PM samples exhibited cytotoxic effect on HEK 293T cells (IC

Despite intensive research carried out on particulates, correlation between engine-out particulate emissions and adverse health effects is not well understood yet. Particulate emissions hold enormous significance for mega-cities like Delhi that have immense traffic diversity. Entire public transportation system involving taxis, three-wheelers, and buses has been switched from conventional liquid fuels to compressed natural gas (CNG) in the Mega-city of Delhi. In this study, the particulate characterization was carried out on variety of engines including three diesel engines complying with Euro-II, Euro-III and Euro-IV emission norms, one Euro-II gasoline engine and one Euro-IV CNG engine. Physical, chemical and biological characterizations of particulates were performed to assess the particulate toxicity. The mutagenic potential of particulate samples was investigated at different concentrations using two different Salmonella strains, TA98 and TA100 in presence and absence of liver S9 metabolic enzyme fraction. Particulates emitted from diesel and gasoline engines showed higher mutagenicity, while those from CNG engine showed negligible mutagenicity compared to other test fuels and engine configurations. Polycyclic aromatic hydrocarbons (PAHs) adsorbed onto CNG engine particulates were also relatively fewer compared to those from equivalent diesel and gasoline engines. Taken together, our findings indicate that CNG is comparatively safer fuel compared to diesel and gasoline and can offer a cleaner transport energy solution for mega-cities with mixed-traffic conditions, especially in developing countries.

A simple synthesis for the integration of different nanoparticles (NPs) including Ag, Au, Pd, Cr and mixed (Cu/Fe), has been demonstrated within the nanopores of a non-activated one dimensional porous coordination polymer (PCP) of Cd(II) due to its high flexible structure. There are two different mechanisms (acid formation (HCl/HNO 3 ) and redox activity of the framework) elucidated by electron paramagnetic resonance (EPR). Presence of –NO 2 groups of the ligand act as anchoring sites for metal ions of metal precursors leading to NPs growth within the PCP explained by FTIR. High resolution transmission electron microscopy (HRTEM) images provided insight of the chemical and physical characteristics of the NPs within the framework. Ag/AgO NPs exhibit excellent antibacterial properties at extremely low concentrations. The polymer shows potential for sequestration and reduction of hexavalent Cr (highly toxic) to elemental, trivalent and tetravalent Cr (non toxic). This framework is also an excellent template for fabrication and dry storage of nanoparticles synthesized by mixed metal precursors. Ferromagnetic properties have been shown by Ag and Au NPs integrated frameworks while Cu/Fe@Cd-PCP behaves as a paramagnet material at room temperature.

In this study, the spray and combustion phenomena of biodiesels were investigated in a constant volume combustion chamber (CVCC). Mineral diesel was used as a baseline fuel and biodiesels derived from waste cooking oil, Karanja oil, and Jatropha oil were utilized to investigate the effect of fuel properties on spray and combustion processes. Experiments were performed at high temperature and pressure conditions in order to simulate the atmospheric environment of a diesel engines. Test fuels were injected at an injection pressure of 80 MPa using a common-rail equipped solenoid injector. Macroscopic evaporation characteristics were analyzed by high-speed shadowgraphy technique under evaporating conditions. The representative droplet size distribution and Sauter mean diameter (SMD) were measured using the Phase Doppler Interferometry (PDI) technique, which was applied to study the spray atomization characteristics of the fuels. The air-fuel equivalence ratio in the spray was calculated using mathematical correlations. The quantitative estimations of soot generation in the spray flames were compared using Hue number analysis. From the shadowgraphy images, the biodiesels showed slower air-fuel mixing characteristics than the baseline diesel due to their inferior volatility. While diesel evaporated abruptly after the fuel injection, the biodiesels showed dense liquid regions in the center of the spray plume. Biodiesels also exhibited larger SMD than the baseline mineral diesel in the fuel spray because of their higher density, viscosity, and surface tension. Despite having poor spray atomization characteristics, the calculated equivalence ratio of biodiesels was lower than that of the baseline diesel. This trend was attributed to the oxygen content of biodiesel. The flame luminosity and visible spray flame duration of biodiesels were lower than those of diesel, while the biodiesel spray flames exhibited lower sooting tendency than the baseline diesel.

Immobilization of the nanoparticles (NPs) in a two dimensional porous coordination polymer (PCP) is currently an emerging field for a number of applications. But still it is a great challenge to fabricate any specified metal NPs in a single network. Herein the synthesis of Au, Pd, Mn, Fe, Cu, Zn, Mg, Li, Fe/Cu, Zn/Mg etc, NPs in a highly flexible PCP of Ni(II); {[Ni3(TBIB)2(BTC)2(H2O)6]·5C2H5OH·9H2O}n [TBIB = 1,3,5-tri(1H-benzo[d]imidazol-1-yl)benzene, H3BTC = 1,3,5-benzenetricarboxylic acid] have been reported. This universal host is able to grow mixed metal NPs from mixed metal precursors. Monodentate carboxylate groups of BTC linker act as anchoring sites for the metal ions of the metal precursors. This is the main driving force to grow NPs within the cavities along with the high flexibility of this polymer at room temperature. Mechanism involves acid formation followed by redox reaction to synthesize metal NPs explained by EPR and FTIR. Paramagnetic properties have been shown by as-synthesized Fe NPs integrated framework at room temperature under applied magnetic field up to 17,500 Oe.

A variety of nanoparticles (NPs) including Ag, Au, Pd, Cr and mixed Cu/Fe have been synthesized in a non-activated (without solvent removal) one dimensional coordination polymer (CP) of Zn(II) via two different mechanisms, acid formation and redox activity of the framework. Main driving force to grow these NPs within the cavities of CP is the presence of free oxygens of one of the monodentate carboxylate groups of BDC ligand. These free oxygens act as anchoring sites for the metal ions of the metal precursors. Chemical and physical characteristics of the NPs within the framework have been evaluated by the high resolution transmission electron microscopic (HRTEM) images. Excluding Ag(0) and Pd(0) other NPs are present as combinations of their elemental as well as oxide forms (Au/Au2O3, Cr/Cr2O3/CrO2 and Cu/Cu2O, Fe/FeO). Synthesized Ag NPs within the framework show remarkable antibacterial efficacy at extremely low concentrations. Ag, Au and Cu/Fe NPs show ferromagnetic properties within the framework at room temperature. This polymer has potential to sequester highly toxic Cr(VI) to non toxic Cr(0), Cr(III) and Cr(IV) species.

Herein, a one step in situ co-synthesis of porous coordination polymers of Ni(II), Co(II) and Mn(II) encapsulating Ag/Ag2O and Au/Au2O3 nanoparticle clusters (spheres and rods) is reported by employing precursors of metal and PCPs, under hydrothermal conditions. No surfactant and reductant have been used. After synthesis of these clusters at high temperature they come out from the cavities of polymers and nucleation process continues inside the cavities. These Ag/Ag2O and Au/Au2O3 nanoclusters encapsulated frameworks show strong paramagnetic and ferromagnetic (soft) properties respectively at room temperature. While electrical characterization data shows that Ag/Ag2O/PCP displays very high conductivity in the range of 1.80×104 S/m which represents the higher end of semiconductance in comparison to Au/Au2O3/PCP which has conductance of 5.9×10−4 S/m representing semiconductivity in the lower mid range at room temperature.

Non corrosive gas, such as CO 2 , is an environment greenhouse pollutant, but at the same time it is a reusable material with a highly attractive application profile and potential as a building block to create added value for the chemical industry. Current technologies for carbon capture are cumbersome, energy intensive and expensive. However, amongst new developments, porous coordination polymers (PCPs) are being viewed as materials with great potential for CO 2 capture. The ability to flexibly design and tune properties of such materials results in different levels of affinity for CO 2 sorption/desorption. Imidazole/benzimidazole and benzoic acid based coordination polymers are of interest from the view point that various architectures such as rigid, flexible, interpenetrating, etc., can be designed to influence cavity pore size and different types of supramolecular interactions existing within the pores. CO 2 sorption, in these structures, not only depends on surface area and void volume but is also influenced by the electronic environment, i.e., functionalization of the pores with either coordinatively unsaturated metal ions or Lewis base groups. In this review, other important influencing factors including strong non-covalent interactions (π-π bonding, anion-π bonding, CH-π bonding, and H-bonding) present on the pore walls, facilitating selective adsorption of CO 2 molecules in substantial quantities (even if Langmuir surface area is very low) are discussed. These interaction potentials in the pores decide quantitatively the sorption of CO 2 as function of temperature and pressure.

Diesel engine emissions consist of several harmful gaseous species, some of which are regulated by stringent emission norms, while many others are not. These unregulated emission species are responsible for adverse environmental impact and serious health hazards upon prolonged exposure. In this study, a four-cylinder, 1.4 l, compression ignition (CI) engine was used for characterization of unregulated gaseous exhaust emissions measured at 2500 rpm at varying engine loads (0, 25, 50, 75 and 100%). The test fuels investigated were Karanja biodiesel blended with diesel (KB5, KB20), methanol blended with diesel (M5) and baseline mineral diesel. Fourier transform infrared (FTIR) emission analyzer was used to measure unregulated emission species and raw exhaust gas emission analyzer was used to measure regulated emission species in exhaust. Results show an increasing trend for some of the unregulated species from blends of biodiesel such as formaldehyde, acetaldehyde, ethanol, n-butane however methane reduced upon using these oxygenated fuel blends except methanol, compared to baseline mineral diesel. Nevertheless, no significant changes were observed for sulfur dioxide, iso-butane, n-octane, n-pentane, formic acid, benzene, acetylene and ethylene upon using biodiesel and methanol blends.

In this study, spark ignition of hydrogen enriched natural gas (HCNG), a fast emerging alternative gaseous fuel, was experimentally investigated in a suitably modified single cylinder spark ignition (SI) engine. Port fuel injection of the HCNG engine using a high volume flow rate solenoid injector, controlled by a customized injector control unit and electronic control unit (ECU) was done and the fuel injection timings and duration were controlled for each load. Fuels with different H/C ratios in the final HCNG mixture were investigated for their engine performance, emissions and combustion characteristics. Engine investigations were carried out at constant engine speed of 1500 rpm for different H/C ratios (4, 4.22, 4.5, 4.85, 5.33 and ∞). Spark timing was kept constant (32° bTDC) for all test blends. Relative air–fuel ratio (RAFR) was kept constant for all loads during the experiments in order to avoid misfire at lower engine load. Hydrogen exhibited higher pressure peak (Pmax) but lower maximum brake torque (MBT) compared to other test fuels due to lower knocking limit. Brake thermal efficiency (BTE) was superior for test fuel with H/C: 4.5. NOx emissions were higher for test fuel with H/C: 4.22 and relatively lower for hydrogen compared to baseline natural gas.

Ag, Au and Cu NPs have been encapsulated within as-synthesized 2D flexible porous coordination polymer {[Zn(TBIB)(HTCPB)]∙2DMF·H2O}n [TBIB = 1,3,5-tri(1H-benzo[d]imidazol-1-yl)benzene, H3TCPB = 1,3,5-Tris(4′-carboxyphenyl-)benzene] 1 at room temperature without employing any reducing agent. Presence of monodentate carboxylate along with the non-coordinated carboxylic acid groups (−COOH) are the main driving forces towards the synthesis of NPs from the polymer. Ag and Cu NPs synthesis takes place through acid formation (HNO3/HCl) while Au NPs have been synthesized by the redox activity of the polymer, elucidated by the electron paramagnetic resonance (EPR). Chemical and physical characteristics of the NPs have been provided by HRTEM. The coordination polymer not only synthesizes the NPs but also prevents them from agglomeration acting as a protective membrane to store fabricated NPs. Magnetic measurements show that all of the NPs integrated polymers reveal ferromagnetic properties at room temperature.

A two-fold interpenetrated, three dimensional Zn-based porous MOF, {[Zn(BPBA)Cl]⋅5H2O}n (1) [BPBA = 3,5-bis-(4-oxo-4H-pyridin-1-yl)-benzoate], has been synthesized at high temperature under solvothermal conditions by the in situ acidic hydrolysis of the tripodal ligand 3,5-bis-(4-oxo-4H-pyridin-1-yl)-benzonitrile (BPBN). The de-solvated MOF exhibited selective CO2 adsorption at a temperature of 195 K and 1 bar pressure over N2 and H2. Interestingly, the four coordinated Zn(II) sites in the MOF exhibited high Lewis acidic heterogeneous catalytic activity for the synthesis of naphthimidazole in excellent yield without pre-activation of the MOF. The Zn(II) sites could directly coordinate to the substrate to catalyze the chemical transformation by an expansion of the coordination number. The π-π supramolecular interactions between the aromatic rings of the framework and the substrate molecule might help in the substrate activation.

A novel two dimensional (2D) porous coordination polymer {[Ni3(TBIB)2(BTC)2(H2O)6]·5C2H5OH·9H2O}n (1) [TBIB = 1,3,5-tri(1H-benzo[d]imidazol-1-yl)benzene, H3BTC = 1,3,5-benzenetricarboxylic acid] has been synthesized solvothermally. In 1, layers are stacked in ABAB⋯ fashion by virtue of strong intermolecular hydrogen bonding interactions, to generate an overall 3D supramolecular framework consisting of isolated pockets accommodated solvent molecules inside. These lattice-constituent solvent molecules are replaced by dichloromethane (DCM), after immersing complex 1 in DCM for seven days at room temperature, yielding {[Ni3(TBIB)2(BTC)2(H2O)6]·6CH2Cl2·6H2O}n (2). Arrangement of layers is slightly changed in compound 2 wherein, small pockets are completely absent. Characterization of these two compounds 1 and 2 has been performed employing, single crystal X-ray diffraction, IR spectroscopy, thermogravimetry and elemental analysis. Importantly, complex 1 shows selective sorption of CO2 gas at low temperature and pressure, and simultaneously displays high heterogeneous catalytic activity for Knoevenagel condensation at high temperature.

Two one dimensional coordination polymers of Cd(II) and Zn(II), {[Cd(NPBI)(BDC)(H2O)]·2H2O}n (1) and {[Zn(NPBI)(BDC)]·H2O}n (2), [NPBI = 1,1′-(4-nitro-1,3-phenylene)bis(1H-benzo[d]imidazole), BDC = 1,3-benzenedicarboxylate] have been synthesized under solvothermal conditions. Both compounds have been characterized by single X-ray crystallography, IR spectroscopy, TGA and elemental analysis. These one dimensional (1D) structures are further stacked to three dimensional (3D) supramolecular framework through polar packing which arises through intensive hydrogen bonding interactions giving rise to 1D dumbbell shaped small cavities which accommodate lattice water molecules. After removal of solvent molecules, permanent porosity in complex 1 with 13.6% void volume was verified by CO2 sorption isotherm that shows selective CO2 gas uptake at low temperature (195 K) as well as at ambient temperature conditions (273 K and 298 K). Topological analysis shows that coordination polymer 1 possesses uninodal 4-connected SP1-periodic net with point symbol {33.42.5} and compound 2 assumes 3-connected SP1-periodic net with point symbol {42.6}.

Proton conductivity is shown for a previously reported, porous coordination polymer {[Mn 2 (DBIBA) 3 ]·(NO 3 )·3DMF·4H 2 O} n , [DBIBAH = 3,5-di(1H-benzo[ d ]imidazol-1-yl)benzoic acid] consisting of hexagonal cavities. Nitrate ions and water molecules are present in the central part of the cavity forming a well defined one dimensional extended hydrogen-bonding network. This framework was revealed to be a proton conductor by temperature dependent study at 100% relative humidity (RH). The proton conductivity was 1.64 × 10 − 4 S·cm − 1 , 2.36 × 10 − 4 S·cm − 1 and 3.09 × 10 − 4 S·cm − 1 at 30%, 50% and 70% RH respectively.

Through in situ basic hydrolysis of cyanide functional group of 3-(1H-benzo[d]imidazol-1-yl)-5-(1H-imidazol-1-yl)benzonitrile a new three dimensional porous coordination polymer {[Co2(BIIBA)3]·(NO3)·5H2O}n (1) (BIIBA = 3-(1H-benzo[d]imidazol-1-yl)-5-(1H-imidazol-1-yl)benzoate) have been isolated under hydrothermal conditions and characterized by single crystal X-ray diffraction. Topological analysis of 1 revealed a (3,3,4,5)-connected 4-nodal unprecedented pkb8 net with point symbol {4.62}2{42.66.82}{63}{65.8}.

By using the tripodal ligand 1,3,5-tri(1H-benzo[d]imidazol-1-yl)benzene (TBIB) and the carboxylate donor ligand 1,3,5-benzenetricarboxylic acid (H 3 BTC), two new coordination polymers, {[Cd 3 (TBIB) 4 (BTC) 2 ]·2C 2 H 5 OH·11H 2 O} n ( 1 ) and {[Zn(TBIB)(HBTC)]·3H 2 O} n ( 2 ), have been obtained under solvothermal conditions. Characterization has been done through X-ray crystallography, IR spectroscopy, thermogravimetry and elemental analysis. Complex 1 displays a novel three dimensional (3D) (3,3,3,3,4,5,5)-connected 7-nodal net with a unique {4.5.6.7 2 .8 3 .9 2 }{4.5.7}{4.5 2 .8 3 }{4.6.7}{4.8 2 } 2 {4 2 .5 2 .8 3 .9 3 } topology while compound 2 reveals a 1D ladder structure which is further extended into a 3D supramolecular architecture through non-covalent hydrogen bonding, C–H⋯π and O–H⋯π interactions, consisting of a 3-connected SP1 -periodic net with the point symbol {4 2 .6}. The metal-free ligand TBIB exhibits strong fluorescence, while this is quenched in both coordination polymers.

The bifurcated ligand 5-di(1H-benzo[d]imidazol-1-yl) benzonitrile (DBIBN) under solvothermal condition, undergoes basic as well as acid hydrolysis to the corresponding carboxylic acid (DBIBA). Four new coordination polymers; {[Cd(DBIBA)(CH3COO)]} n (1), {[Zn(DBIBA)(CH3COO)]⋅H2O} n (2), {[Zn(DBIBA)(OC2H5)]⋅H2O} n (3) and {[Co(DBIBA)(CH3COO)]⋅H2O} n (4) have been synthesized under solvothermal conditions. Compound 1 has a 3D structure with uninodal 4-connected crb/BCT topology with point symbol of {4.65}. In contrast, compounds 2–4 are 2D layered structures having uninodal 3-connected hcb net with a vertex symbol of {63}. The 2D layers are further assembled to an overall 3D supramolecular architecture with strong π–π interactions between layers. Further reinforcement of the 3D assembly occurs due to an array of H-bonding interactions with lattice water molecules present within the layers. All the compounds have been characterized by single X-ray crystallography, IR spectroscopy, TGA, PXRD measurements and elemental analysis. Although the metal-free DBIBN ligand exhibits fluorescence, it is quenched in the coordination polymers.