Porous structures and adsorption phenomena in rare-earth element phosphates and bridged resorcinarene cages elucidated by combined experimental and computational 31P and 129Xe NMR

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Martti Ahtisaari -hall (L2) of the University of Oulu, Pentti Kaiteran katu 1

Topic of the dissertation

Porous structures and adsorption phenomena in rare-earth element phosphates and bridged resorcinarene cages elucidated by combined experimental and computational 31P and 129Xe NMR

Doctoral candidate

Master of Science Roya Khalili

Faculty and unit

University of Oulu Graduate School, Faculty of Science, NMR Research Unit

Subject of study

Physics

Opponent

Doctor of Philosophy Elina Sievänen, University of Jyväskylä

Custos

Professor Ville-Veikko Telkki, University of Oulu

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Porous structures and adsorption phenomena in rare-earth element phosphates and bridged resorcinarene cages elucidated by combined experimental and computational 31P and 129Xe NMR

The aim of the present thesis is to unravel the structure and adsorption properties of essential materials that have a broad range of applications from environmental science to technology. Studied materials are rare-earth element phosphates and resorcinarene cages. Using NMR spectroscopic techniques, we probed the structures and micro/nano scale pores of these materials. DFT computational methods were applied to interpret experimental results, as well as to provide molecular-level understanding of the investigated systems.
Firstly, we determined the configuration of water molecules in rare-earth element phosphates and characterized the surface and pore structures of the samples. Rare-earth element phosphate samples included lanthanum, samarium, lutetium and ytterbium phosphates. Here, for the first time, we studied rare-earth element phosphates applying 129Xe NMR, a technique which is highly sensitive to the chemical environment and which can provide detailed information on the structures of porous materials. 129Xe NMR analysis was complemented by 31P solid-state NMR to provide additional information on the local structures and the coordination of water molecules on surfaces. Complementary information from quantum chemical calculations enabled the identification of several surface structures and confirmed the experimentally observed bulk phases. Additional structural characterization of these materials was obtained by PXRD, TGA, LDS, FTIR and FESEM methods.
Secondly, we investigated supramolecular cage molecules based on bridged resorcinarene macrocycles, which are new, promising and affordable potential cages for 129Xe NMR biosensor applications. Computational modelling predicted unique chemical shifts of 129Xe in the cages, and chemical exchange saturation transfer and relaxation experiments revealed fast xenon exchange dynamics, which is favorable for biosensor applications.

Keywords: adsorption properties, rare-earth element phosphates, Xe biosensors, bridged resorcinarene cages, NMR, 31P, 129Xe, DFT, CEST.
Last updated: 24.11.2022