Synthesis of modified Metal-Organic Frameworks (MOFs) for gas storage

Details

Supervisors

Hermans, Sophie ; Filinchuk, Yaroslav ; Steenhaut, Timothy

Faculty

Faculté des sciences

Degree label

Master [120] en sciences chimiques, à finalité spécialisée: chimie de l'industrie

Abstract

This project focused on the synthesis, modification and sorption properties of various metal-organic frameworks (MOFs). It is divided into four experimental parts covering respectively: the functionalization of MIL-101(Cr) for acidic gas sorption, synthesis strategies towards flexible manganese-based MIL-53 type MOFs, the inclusion of palladium nanoparticles in MOFs, and performing high-quality volumetric H2 sorption measurements. In the first part, MIL-101(Cr), MIL-101(Cr)-NH2, and amine-functionalized MIL-101(Cr) (amine = ethylenediamine and tris(2-aminoethyl)amine) were synthesized and characterized. Successful syntheses were confirmed through X-ray diffraction, spectroscopic techniques, elemental and nitrogen sorption analyses. Amine-functionalized MIL-101(Cr) showed improved CO2 sorption compared to pristine MIL-101(Cr), both in terms of capacity, but also in terms of very high adsorption enthalpy at low loadings (-50 kJ/mol). Structural integrity was maintained for MIL-101(Cr) and amine-functionalized MIL-101(Cr) during H2S and SO2 sorption, although some deterioration of the MOF structure occurred with SO2. This functionalization approach demonstrates potential for reversible H2S adsorption. The second part addresses structural modification strategies of a Mn-based MIL-53 derivative containing methoxy ligands, with the aim to explore its flexibility. Changing the synthesis solvent to ethanol leads to a phase-pure sample with a new structure, showing flexibility upon heating. The use of 2,6-naphthalenedicarboxylate as an extended (larger) linker was shown effective, leading to a MIL-69 type structure. Finally, the synthesis of multivariate MIL-53(Mn) MOFs with 2-nitroterephthalate linkers were investigated, leading to progressive pore opening with increased substitution by the functionalized linker. In the third part, we investigated the incorporation of palladium in MIL-100(Fe) and MIL-101(Cr). The reaction of MIL-100(Fe) in water/EtOH mixtures resulted in the formation of Pd0 particles, with the solvent composition influencing their size and distribution. Concerning MIL-101(Cr), successful impregnation of (CF3COO)2Pd was realized on the amine-functionalized MOF while maintaining its structure. Finally, in the fourth part, challenges related to volumetric measurements were addressed, including reactor calibration, thermostat partitioning, and determination of displacer density. A clear protocol was developed for simple gas sorption measurements, and its effectiveness shown by conducting hydrogen sorption measurements on four MOF samples in a reliable fashion. H2 adsorption enthalpies were reliably determined from these data.