Carbon dioxide capture enhanced by pre-adsorption of water and methanol in UiO-66

The rapidly rising level of carbon dioxide in the atmosphere resulting from human activity is one of the greatest environmental problems facing our civilization today. Most technologies are not yet sufficiently developed to move existing infrastructure to cleaner alternatives. Therefore, techniques for capturing carbon dioxide from emission sources may play a key role at the moment. The structure of the UiO‐66 material not only meets the requirement of high stability in contact with water vapor but through the water pre‐adsorbed in the pores, the selectivity of carbon dioxide adsorption is increased. We successfully applied the recently developed methodology for water adsorption modelling. It allowed to elucidate the influence of water on CO(2) adsorption and study the mechanism of this effect. We showed that water is adsorbed in octahedral cage and stands for promotor for CO(2) adsorption in less favorable space than tetrahedral cages. Water plays a role of a mediator of adsorption, what is a general idea of improving affinity of adsorbate. On the basis of pre‐adsorption of methanol as another polar solvent, we have shown that the adsorption sites play a key role here, and not, as previously thought, only the interaction between the solvent and quadrupole carbon dioxide. Overall, we explained the mechanism of increased CO(2) adsorption in the presence of water and methanol, as polar solvents, in the UiO‐66 pores for a potential post‐combustion carbon dioxide capture application

The application of distributed optical fiber sensors (BOTDA) to sinkhole monitoring. Review and the case of a damaging sinkhole in the Ebro Valley evaporite karst (NE Spain)

Distributed optical fiber sensors (DOFS) have been postulated as a suitable technique for long-range monitoring of sinkhole-related subsidence, and possibly for the anticipation of catastrophic collapse (early-warning systems). The strain data published in previous works refer to artificial experiments considering real and virtual cover collapse sinkholes characterized by rapid subsidence and sharp lateral deformation gradients. The influence of the subsidence mechanism (sagging, collapse, suffosion) on the capability of DOFS to satisfactorily detect active subsidence is discussed. Sagging sinkholes with poorly-defined lateral edges, low lateral deformation gradients and slow subsidence are identified as the most challenging scenario. The performance of BOTDA optical fiber for monitoring such type of sagging sinkholes is evaluated in the active Alcalá sinkhole, which affects a flood-control dike creating a high-risk and -uncertainty scenario. This sinkhole shows active subsidence in sections tens of meters long with maximum subsidence rates ranging between 5 and 35 mm/yr. The comparison of vertical displacement data measured by high-precision leveling and the strain recorded by two types of fiber optic cables shows good spatial and temporal correlation. The subsidence sections are captured in the strain profiles by: (1) troughs of negative strain (contraction) in the area affected by subsidence, with the maximum strain associated with the point of most rapid settlement; and (2) lateral ridges of positive values (extension) in the marginal zones. A subsidence acceleration phase associated with a flood is also captured by substantial increments in the strain values. In this challenging scenario, despite the reasonably good spatial and temporal correlation between the displacement and strain data, the unambiguous identification of the active subsidence area with the fiber optic data alone might be difficult. Better results could be obtained improving the monitoring system (e.g., tighter cable-ground coupling) and testing other types of sinkholes with more localized deformation zones and higher subsidence rates

Governmental Context Determines Institutional Value: Independently Certified Performance and Failure in the Spanish Newspaper Industry

Many societies demand that independent professionals (e.g. auditors) certify the performance of firms. The value placed on such certification (i.e. the public perception of reliability/unreliability that may impact on an organization's success/failure) is not uniform, however, but contingent upon changing political contexts. This study presents and analyses data on the entire population of newspapers in Spain from 1966 to 1993, a time of peaceful transition from military dictatorship to capitalist democracy. Our results highlight the contingent nature of institutional life, demonstrating how changes in political contexts are associated with varying understandings of institutions. In particular, our findings support the prediction that, under a dictatorship, independently certified performance is not instrumental in organizational success or failure whereas, in a modern democracy, the certification process has a positive effect on the survival chances of firms.Publicad

Enantioselective adsorption of ibuprofen and lysine in metal–organic frameworks

This study reveals the efficient enantiomeric separation of bioactive molecules in the liquid phase. Chiral structure HMOF-1 separates racemic mixtures whereas heteroselectivity is observed for scalemic mixtures of ibuprofen using non-chiral MIL-47 and MIL-53. Lysine enantiomers are only separated by HMOF-1. These separations are controlled by the tight confinement of the molecules

A Simulation Study of Hydrogen in Metal–Organic Frameworks

Molecular simulations have been used to evaluate the effect exerted by metal centres on the adsorption and diffusion of hydrogen in metal–organic frameworks. Simulations were carried out for the MIL-53 (Cr and Al) structures and the isostructural vanadium analogue MIL-47 at room temperature. To validate the models and force fields used in this work, the adsorption isotherms, energies and entropies, and self-diffusivities in Cu–BTC and IRMOF-1 metal–organic frameworks were computed. Using the validated force fields and models, a detailed analysis of the preferential adsorption sites is reported, allowing the energetic contribution in the low-coverage regime (Henry constants and adsorption energies and entropies) to be determined as a function of loading (adsorption isotherms). The influence of each energetic contribution to the charged and uncharged models of hydrogen has also been analyzed

Water adsorption in ideal and defective UiO-66 structures

We combine experiments and simulations to study the adsorption of water in several UiO-66 frameworks (ideal and defect-containing structures). We propose a new set of charges for the frameworks that accurately provides the water-structure interaction at the molecular level. The new set is suitable for predicting water adsorption in the ideal UiO-66 structure, providing for the first time, good agreement between experimental and calculated isotherms. The proposed procedure for tuning the point charges of the framework to achieve agreement with experiments is universal and can easily be extended to other MOFs. We explore the structural characteristics in terms of adsorption of water and the potential application of these materials to water harvesting from air. Our results show that the number of introduced defects significantly affect water sorption properties, which results in shifting steep water uptake and increasing saturation loading. Additional performed experiments, such as Ar sorption and the use of the QE-TPDA method allow for a broad characterization of structure-containing defects and the impact that these defects exert on the properties of the materials

Vertical Displacement Measurement in a Slow-Moving Sinkhole Using BOTDA

Abstract The effectiveness of monitoring and early-warning systems for ground deformation phenomena, such as sinkholes, depends on their ability to accurately resolve the ongoing ground displacement and detect the subtle deformation preceding catastrophic failures. Sagging sinkholes with a slow subsidence rate and diffuse edges pose a significant challenge for subsidence monitoring due to the low deformation rates and limited lateral strain gradients. In this work, we satisfactorily illustrate the practicality of the Brillouin optical time domain analysis (BOTDA) to measure the spatial-temporal patterns of the vertical displacement in such challenging slow-moving sagging sinkholes. To assess the performance of the approach, we compare the strain recorded by the distributed optical fiber sensor with the vertical displacement measured by high-precision leveling. The results show a good spatial correlation with the ability to identify the maximum subsidence point. There is also a good temporal correlation with the detection of an acceleration phase in the subsidence associated with a flood event