No abstract

© 2015. This manuscript version is made available under the Elsevier user license In this study, the effects of acid activation with high bentonite contents under mild synthetic conditions on textural and structural properties were explored. The alteration features after activation were fully characterized with the help of X-ray powder diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area, Barrett-Joyner-Halenda (BJH) pore size and volume analyses. The active sites were examined using volumetric titration and confirmed with a pyridine adsorbed FT-IR study. The activated bentonite (ABn) was further utilized for the removal of Cu(II) and Pb(II) ions from aqueous solutions. Batch reactor studies showed that the removal of these toxic metal ions was favored by increases in the pH, initial metal concentrations, contact time, and dose of the adsorbents. The equilibrium data obtained at various initial concentrations reasonably fit well with the Langmuir and Freundlich adsorption isotherms. The adsorption process was fast and the kinetic data fit better to the pseudo-second order kinetic model. The presence of other heavy metal ions, such as Cd(II), Fe(II), and Mn(II), did not significantly suppress the removal of both the Cu(II) and Pb(II); whereas the other cations, such as Na + , K + , Ca 2+ , and Mg 2+ , caused a notable decrease in the Pb(II) removal. In addition, the breakthrough data obtained in the column studies fit well with the non-linear Thomas equation, and high loading capacities of Cu(II) and Pb(II) were obtained. Therefore, we demonstrated in this study that the low cost 'ABn' solid can be employed as a potential adsorbent for the effective treatment of aqueous waste contaminated with Cu(II) and Pb(II).

Astute combination of basic functionality and luminescence property can pursue multifunctional metal−organic frameworks (MOFs) with assorted applications such as selective CO 2 adsorption, specific detection of explosive nitro compounds, and toxic metal ion sensing. The bifunctional ligand 4-(4-carboxyphenyl)-1,2,4-triazole (HL) is used to build the framework [Cd(L) 2 ]•(DMF) 0.92 (1) (L = L −1 , DMF = N,N′-dimethylformamide), having a free N atom decorated porous channel. The solvothermal synthesis is extended to produce three isoskeletal frameworks in diverse solvents, where pore size maximizes in 2 by employing N,N′-diethylformamide solvent. The activated framework [Cd(L) 2 ] exhibits strong CO 2 affinity with good CO 2 /N 2 selectivity, and shows minimum CO 2 loss during five adsorption−desorption cycles. Sensing studies for nitro-aromatic compounds in DMF reveal highly specific detection of 2,4,6-trinitophenol (TNP) with remarkable quenching (K SV = 9.3 × 10 4 M −1 ) and low limit of detection (LOD: 0.3 ppm). The quenching mechanism is ascribed to the combined existence of static and dynamic quenching plus resonance energy transfer. The activated framework further shows highly selective luminescent detection of Cu 2+ ions with a quenching constant of 4.4 × 10 3 M −1 and very low LOD of 3.9 ppm. The detection of Cu 2+ ions accompanies a visible color change in solution and solid phase, which validates the present system as a potential colorimetric Cu 2+ sensor. Of note is that bifunctional sensor shows excellent reusability toward TNP and Cu 2+ detection. Overall, selective and multicycle CO 2 adsorption, together with efficient sensing of both TNP and Cu 2+ ion, manifest this pore-functionalized MOF as a versatile material for sustainability.

FeII to RuIII electron transfer is initiated by the inclusion of saturated bridging ligands into the β‐cyclodextrin (CD) cavity of [2]rotaxane complexes and is observed as an intervalence charge transfer (IVCT) band in the electronic spectra (see picture). The rotaxanes are synthesized by using RuIII and FeII complexes as stoppers, β‐CD as the cyclic molecular head, and 4,4′‐bipyridine derivatives with interrupted π‐electron system as the bridging ligand between the metal centers.

Herein, we report the synthesis, characterization, and application of uniformly dispersed palladium nanoparticles supported on cucurbit[6]uril. The 2.56 wt% Pd was loaded on cucurbit[6]uril by impregnation method. Cucurbit[6]uril is a macrocyclic compound in which six glycoluril units are joined with twelve methylene bridges which not only act as support but also helped in stabilizing Pd nanoparticles. The synthesized catalyst was thoroughly characterized by various physicochemical methods. The high resolution transmission electron microscopic analysis revealed the uniform distribution of Pd nanoparticles with average size of ∼3 nm over the cucurbit[6]uril surface. Furthermore, the synthesized catalyst was used for the chemoselective hydrogenation of various reducible (epoxide, olefin, carbonyls, nitrile, azo, imines and nitroarenes) groups with excellent conversion, selectivity (> 99%) and high turnover frequency (up to 2,05,882 h−1) in aqueous and in some cases with water‐THF mixture. Also, the catalyst was successfully recycled several times (>10 times) without losing any significant conversion and selectivity. Moreover, the leaching results were confirmed by analyzing reaction mixture by inductively coupled plasma atomic emission spectroscopy. Furthermore, the kinetic studies reveal the reaction rate depends on substrate concentration. The reaction mechanism was investigated by studying the reaction through drift FTIR studies.