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 of the fundamental building blocks of growth and/or intermediate phases is thus of profound interest, but appears to be a great experimental challenge. In this article we studied the competitive formation of two porous iron carboxylates by using X-ray absorption and Mössbauer spectroscopies. By detailed investigation of different stages of synthesis from solution to the formation of final crystalline products, we succeeded to demonstrate how the presence of aprotic solvent changed the formation mechanism from the very beginning of the synthesis (type and structure of primary building blocks, oxidation state of iron at elevated temperatures). It is the first study that evaluates the role of the solvent in the MOF formation process by analyzing the local structure of species that are present in the precursor solution and gel. The study was published in Angewandte Chemie International Edition (impact factor 13.5).
COBISS.SI-ID: 36300805
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. In this paper we proposed a model that predicts the heat storage potential of numerous known or new microporous aluminophosphates. A comparative thermogravimetric and calorimetric study of water sorption in small-pore SAPO-34, AlPO4-18 and APO-Tric materials revealed 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. The formation of clusters is enabled by rapid and reversible changes in the framework Al 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
We showed that solid-state nuclear magnetic resonance offers valuable information about the drug molecules that had been incorporated into the mesoporous materials. We were able to very precisely determine the average number of drug molecules within the unit cells and found out that in the channels of the porous materials the drug molecules interact one with another through hydrogen bonds, whereas in the spherical cavities such interactions among the molecules were not detected. In both cases the drug molecules interacted only weakly with the framework. Nuclear magnetic resonance was used also for studying dynamcis of the drug molecules. Such detailed information about drug molecules within the delivery systems could not be obtained by other experimental techniques.
COBISS.SI-ID: 4893978
We presented clear evidence that the macroscopic transport from/to mesoporous materials is significantly affected by the interactions between the mesoporous host and the guest molecules. The problem was considered in a most general way so the solutions apply for a variety of cases such as the release of a guest from porous matrices, catalysis occurring in porous materials or processes taking place in separation techniques. The concept was proved by the experimentally determined release profiles of a model drug (indomethacin) from accurately designed SBA-15 and MCM-41 mesoporous silicates. We showed that the host-guest interactions change the effective cross-section of pores through which the transport of guest occurs. In addition, the interactions lower the efficiency of utilization of the guest. In drug release this is observed as a decrease of released matter at long times, in catalysis this would correspond to a decrease of global turnover efficiency etc. However, it is not only the final outcome that is affected but also the transport pattern (e.g. the shape of release curves). Our finding might have a profound influence on the design of various devices based on mesoporous or macroporous materials.
COBISS.SI-ID: 4837914