We developed a new method for the investigation of spatial distribution of various organic linkers or functional groups within metal-organic materials. The method is based on nuclear magnetic resonance measurement of spin-diffusion rates and modeling of distributions of organic linkers within metal-organic frameworks. It can distinguish between the cases, in which different linkers form domains, and cases, in which different linkers are uniformly distributed throughout the materials. This unique tool can be employed also for studying other heterogeneous or spatially disordered materials.
COBISS.SI-ID: 5735962
We investigated the preferential adsorption of water from gaseous water–ethanol mixtures on porous metal-organic material MIL-100, and developed a successful new characterization approach based on coupling of infrared spectroscopy and in-situ gravimetry. Infrared spectroscopy is a powerful and recognized technique for studying the species adsorbed on materials' surfaces, which allows one to quantify the adsorbates and to characterize the active sites. In-situ gravimetry permits one to determine the mass adsorbed under different relative pressures. Coupling of the two techniques is essential for the determination of the molar absorbance coefficients for the characteristic vibration bands of adsorbates. The presented approach allows one to study the material's performance not only for water/ethanol separation, but also to study the adsorption of other vapor mixtures onto porous materials.
COBISS.SI-ID: 5760026
Microporous zeolite-like aluminophosphate AlPO4-34 is a very promising material for water-adsorption-based thermal energy storage. To obtain better understanding of the dehydration of this material, we carried out a detailed variable-temperature nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and first-principles calculation study. We detected three distinct steps (phase transitions) during the dehydration. XRD and NMR were complementary to one another, not only in the sense that XRD yielded information on the average periodic long-range structure and that NMR offered an insight into the local environment of atomic nuclei and on the dynamics within the material, they also worked with very differently packed samples and because of that detected very different dynamics of dehydration. And whereas sensitivity to sample packing may had complicated the comparison of the experimental results obtained by NMR and XRD, the manifestation of this sensitivity also pointed out the very important role that packing of material will have in the potential large-scale applications of AlPO4-34 for energy conversion or heat storage.
COBISS.SI-ID: 5835546