The work presented in this article is aimed to assess the performances of 4763 Metal−Organic Frameworks (MOFs) for separation of hexane isomers using computer simulation methods. These MOFs, taken from the Computational Ready Experimental (CoRE) MOF database, are ranked on the basis of various performance metrics, namely, adsorption selectivity, working capacity, and regenerability. We investigated six binary mixtures, one three-component equimolar mixture, and one five-component equimolar mixture of hexane isomers at temperatures of 383, 433, 483, and 533 K. The MOFs were ranked separately for separation of each of these mixtures. The rankings with respect to these three metrics were found to be mostly different with only a few MOFs in common. We also carried out the rankings at different temperatures close to the typical isomerization reactor temperature. It is observed that the orders of the rankings at different temperatures are different. However, the majority of the MOFs are found to be common in the rankings at different temperatures. MOFs BIMDOR and WAMRIN01 perform the best with high adsorption selectivity for all the mixtures. It is observed that the MOFs with very high adsorption selectivity do not have high working capacity and regenerability. However, MOFs VEHJOJ, VEHJUP, and NAYGUR are found to be potential candidates for practical application of separation of the hexane isomers as they have regenerability >80% and reasonably high working capacity and adsorption selectivity. Further, we looked at various structures' property correlations. These correlations reveal that the largest cavity diameter and pore volume are crucial structural properties to be adjusted for obtaining the best performing MOF structure with high selectivity, high working capacity, and high regenerability. MOFs with a largest cavity diameter close to 10 Å show high values of selectivity, working capacity, and regenerability.

An oxide semiconductor changes its resistance with exposure of water molecules and is accepted to be governed by electronic and protonic conduction in low and high humid atmosphere, respectively, without any experimental evidences. Here, we report on the experimental evidence of a relative humidity (RH) dependent crossover, from an electronic to protonic conduction and its oscillatory behaviour in mesoporous SnO2. Interestingly, oscillatory conduction observed in the intermediate humidity range (70%–90% RH) lies in between two monotonic variations that substantiate the competitive adsorption and desorption processes of oxygen species and water molecules. In addition, we have shown that the conduction process can be tuned predominantly electronic or protonic by pre- and post-UV treatment. The conductance increases by 2–3 orders as the conduction changes from pure electronic to protonic, suggesting an insulator-to-metal like transition.

Highly porous materials, with large surface area and accessible space, variable chemical compositions, and porosity at different length scales, have captivated the attention of researchers in recent years as an important family of functional materials. Here, we report a novel approach to grow porous metal oxides (PMOs) by sequential elemental dealloying in which a highly mobile element gets dealloyed first under the thermal treatment (annealing) and facilitates the formation of PMOs. Subsequently, a chemiresistive sensor based on porous SnO was fabricated for humidity sensing at room temperature which shows a high sensitivity of 348 in a fully humid [>99% relative humidity (RH)] atmosphere with an accuracy of 1% RH change. In addition, the sensor is highly durable and reproducible. Eventually, the chemiresistive sensor has been exploited for electronic listening toward speaking, whistling, and breath monitoring. Overall, the results advocate the fabrication of PMOs and the development of resistive humidity sensors for electronic listening as well as for biomedical applications.

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Molecular modelling and computational science tools were employed to select a number of metal−organic frameworks (MOFs) from a pool of 4764 structures to investigate and assess their kinetic and adsorption-based separation performances in separating hexane isomers. The self-diffusivities of all single-component isomers were obtained from molecular dynamics simulations at infinite dilution and at a loading of 4 molecules/unit cell and at several temperatures. The self-diffusivities of the binary mixtures of the hexane isomers were also computed to obtain the kinetic separation metrics. The diffusivities at infinite dilution and at 298 K show a variety of trends as a degree of branching in the chosen MOFs. The linear hexane diffuses faster than other isomers in majority of the MOFs. On the other hand, the MOFs considered here show reverse adsorption selectivity, with the dibranched isomers adsorbing more than the linear one. The diffusivities at infinite dilution, as a function of temperature, of all isomers in the MOFs considered in the present study show Arrhenius behavior. The activation energies calculated from the Arrhenius plots complement the diffusivities. Further, the performances of these chosen MOFs were assessed in separating the linear hexane from the two dibranched ones as well as the dibranched ones from each other. MOF IYIHUU shows the highest membrane selectivity of the dibranched hexanes over the linear one at 433 K and at a pressure of 10 bar. Several MOFs show membrane selectivity of 22DMB over 23DMB, close to two or more indicating their ability to distinguish the two dibranched isomers kinetically.

Crystalline TiO 2 nanodots have been formed on single crystal rutile TiO 2 ͑110͒ surfaces via ion beam sputtering method by utilizing Ar ion beams from electron cyclotron resonance source. Nearly five times enhancement in absorbance of visible light, ϳ5 times increase in luminescence, and ϳ0.1 eV narrowing of bandgap are observed for nanodot-patterned surfaces, in the absence of any dopant material. Formation of crystalline rutile TiO 2 nanodots and development of Ti interstitials on the TiO 2 ͑110͒ surface, after ion beam sputtering, are responsible for these observations. Results suggest that these nanodot-patterned rutile TiO 2 surfaces can become effective photocatalysts.

Water dissociation, in general, requires external stimuli such as light energy or electricity. Here, we present a stimuli-free water dissociation using mesoporous SnO 2 -based hydroelectric cell that can directly be exploited to generate electric power for portable applications. The device configuration is almost identical to metal-air batteries but follows altogether a different reaction pathway. The mesoporous SnO 2 -based hydroelectric cell dissociates water molecule into hydroxyl ions (OH -) and hydronium ion without any stimuli, transports hydronium ions to the opposite end, and simultaneously acts as the separator. The OHreact with Al electrode to release the electrons, whereas hydronium ions get reduced at the Ag electrode to produce a potential difference as high as 1000 ± 20 mV between the electrodes that is stable over 3500 hours. The device also shows its potential toward electric power generation from atmospheric moisture with the help of CuO layer that acts as moisture pump.

Two dimensional nanostructures have been created on the rutile TiO2 (110) surfaces via ion irradiation technique. Enhanced anomalous photo- absorption response is displayed, where nanostructures of 15 nm diameter with 0.5 nm height, and not the smaller nanostructures with larger surface area, delineate highest absorbance. Comprehensive investigations of oxygen vacancy states, on ion- irradiated surfaces, display a remarkable result that the number of vacancies saturates for higher fluences. A competition between the number of vacancy sites on the nanostructure in conjunction with its size is responsible for the observed anomalous photo-absorption.