The understanding of crystallization mechanism is crucial for a rational design of new metal-organic (MOF) porous materials with desired properties for specific applications, like heat and gas storage, gas separations, drug delivery, catalysis, etc. The detection the fundamental building blocks of growth and/or intermediate phases is thus of profound interest, but appears to be a great experimental challenge. Authors of the paper have studied the competitive formation of two porous iron carboxylates by using X-ray absorption (XAS) and Mössbauer spectroscopies. By detailed investigation of different stages of synthesis from solution to the formation of final crystalline products, they succeeded to demonstrate how the presence of aprotic solvent (acetone) changed the formation mechanism from the very first beginning of the synthesis (type and structure of primary building blocks, oxidation state of iron at elevated temperatures) if compared with pure water solution. It is the first study that evaluates the role of the solvent in the MOF formation process by analysing the local structure of species that are present in the precursor solution and gel.
COBISS.SI-ID: 36300805
The authors have developed a mechanism that predicts the heat storage potential of numerous known or new microporous aluminophosphates. The utilisation of the reversible chemical and physical sorption of water on solids provides a new long-term thermal energy storage concept, also in combination with solar thermal collectors. However, up to now there have been no systematic studies of the possible mechanisms for heat storage enhancement concerning materials optimisation. Based on a comparative thermogravimetric and calorimetric study of water sorption in small-pore aluminophosphate materials (SAPO34, AlPO418and APOTric) the authors proposed that the formation of highly ordered water clusters in the pores is a driving force for a sudden water uptake in a narrow relative pressure range, which is a prerequisite for their use in storage systems and crucially determines their sorption efficiency. The formation of clusters is enabled by rapid and reversible changes in the framework aluminium coordination and optimal pore diameters.
COBISS.SI-ID: 4910618
Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most promising industrially applicable advanced oxidation processes for the decomposition of organic pollutants in water. In this article we presented a novel and environmentally friendly, cost-effective as well as highly efficient catalyst for catalytic wastewater purification. We demonstrated that manganese functionalized silicate nanoparticles act as a superior catalyst in WHPCO, since they can completely decompose and convert to carbon dioxide 80 % of a test organic compound in 30 minutes at neutral pH and room temperature. By performing structural characterization of the material using X-ray absorption spectroscopic techniques and catalytic tests, it was also proven that the superior activity of the catalyst can be attributed uniquely to the manganese incorporated into silicate framework of nanoparticles, and not to manganese in the form of manganese oxides (Mn3O4, Mn2O3). The presented material thus introduces a new family of catalysts, which possess superior efficiency for the decomposition of organic pollutants dissolved in water.
COBISS.SI-ID: 4863514
Iron-functionalized silica nanoparticles with inter-particle porosity (FeKIL-2) do act as a highly efficient adsorbent and catalyst for the oxidation of toluene in the gas phase. By using UV/Vis, FTIR, and Mössbauer spectroscopic techniques, we proved that the enhanced activity of the catalyst is attributed to the iron incorporated into the silica matrix and depends on the iron content. The iron content with Fe/Si≤0.01 leads to the formation of stable Fe3+ ions in the silica matrix, which ensures easier oxygen release from the catalyst (Fe3+/Fe2+ redox cycles). The increase in the iron content with Fe/Si)0.01 leads to the formation of oligonuclear iron complexes. The material thus introduces a promising, environmentally friendly, cost-effective, and highly efficient catalyst with combined adsorption and catalytic properties for the removal of low concentrations of VOCs from polluted air.
COBISS.SI-ID: 5150746
Based on the results of carefully designed experiments upgraded with appropriate theoretical modeling, we present clear evidence that the release curves from mesoporous materials are significantly affected by drug-matrix interactions. In experimental curves, these interactions are manifested as a non-convergence at long times and an inverse dependence of release kinetics onpore size. Neither of these phenomena is expected in non-interacting systems. Although both phenomena have, rather sporadically, been observed in previous research, they have not been explained in terms of a general and consistent theoretical model. The concept is demonstrated on a model drug indomethacin embedded into SBA-15 and MCM-41 porous silicates. The experimental release curves agree exceptionally well with theoretical predictions in the case of significant drug-wall attractions. The latter are described using a 2D Fokker-Planck equation. One could say that the interactions affect the relative cross-section of pores where the local flux has a non-vanishing axial component and in turn control the effective transferof drug into bulk solution. Finally, we identify the critical parameters determining the pore size dependence of release kinetics and construct a dynamic phase diagram of the various resulting transport regimes.
COBISS.SI-ID: 4727578