Morphology control in modulated synthesis of metal-organic framework CPO-27

Under embargo until: 2020-08-27The CPO-27/MOF-74 series is among the most investigated metal-organic frameworks because of their usefulness in a diverse range of applications. For specific applications, it will be important to control the shape and size of the particles or crystallites of the material. The modulation approach has been successfully used to direct these parameters in the synthesis of MOFs. Here, we report the synthesis of CPO-27-Ni in the presence of different ratios of benzoic acid and acetic acid as modulators. Yields, powder X-ray diffraction data, scanning electron microscopy results, and elemental, thermogravimetric, and gas sorption analyses are compared to study the influence of the modulator on the product. The results show that we have successfully synthesized pure CPO-27-Ni independent of the amount of modulator. The modulator affects the resulting morphology of the crystalline product with a defined variation of particle sizes and shapes. In addition, ESI-MS has been employed in probing the reaction solutions. It shows the preferred formation of complexes between the metal cation and the modulator, thus indicating that the ligand substitution plays a major role in the crystal growth.acceptedVersio

Design and syntheses of Mn-Anderson based compounds as functional hybrid materials

This thesis focuses on the synthesis of hybrid organic-inorganic polyoxometales (POMs), more precisely Mn-Anderson based complexes; {MnMo6O18((OCH2)3-R)2}. A modular synthetic approach has been designed, resulting in an asymmetrically grafted Mn Anderson compound (compound 3a). Electrospray ionisation mass spectrometry (ESI-MS) was used to screen the batches from fractional crystallisation, identifying the pure material of the desired compound. Two additional symmetrically grafted Mn-Anderson compounds were synthesised containing the same organic ligands (compounds 1a and 2a). The Langmuir-Blodgett (LB) technique was used to deposit monomolecular films of the three isolated compounds on to solid substrates, and subsequently scanning force microscopy (SFM) was used to investigate the resulting architectures. Two of the compounds formed defined anisotropic fibre like structures, and it was found that the resulting surface architectures depend on the nature of the organic ligands employed. For the Mn-Anderson complex which previously did not result in the formation of any defined structures cation exchange from tertbutylammonium (TBA) to dimethyldioctadecylammonium (DMDOA) was successfully performed (compound 1b). SFM investigations of LB deposited films showed perfectly shaped hexagonal nanocrystals. The nanocrystals are of high stability, although by thermal treatment self patterning occurs. Scanning capacitance microscopy (SCM) was carried out, and the hexagonal nanocrystals were found to exhibit fascinating capacitance behaviour. The aforementioned work led to the design and syntheses of a range of organic ligands, along with the corresponding symmetrically grafted Mn Anderson complexes (compounds 1 12), with a diverse range of cations. Systematic SFM studies of LB deposited films of the resulting hybrid organic inorganic Mn-Anderson compounds were carried out with the results described and discussed. Furthermore, the syntheses of three β-octamolybdate salts, along with their ESI-MS analyses, led to the proposal that the fragmentation of β-octamolybdate in solution is similar to that of α-octamolybdate, the traditional starting material for hybrid Mn Anderson compounds. Accordingly, three hybrid organic-inorganic Mn-Anderson compounds were successfully synthesised from the β-octamolybdate isomers (compounds C-J). These syntheses increase the understanding of the one-pot reaction mechanism, and might allow for the syntheses of Mn-Anderson compounds with new cations

Morphology control in modulated synthesis of metal-organic framework CPO-27

The CPO-27/MOF-74 series is among the most investigated metal-organic frameworks because of their usefulness in a diverse range of applications. For specific applications, it will be important to control the shape and size of the particles or crystallites of the material. The modulation approach has been successfully used to direct these parameters in the synthesis of MOFs. Here, we report the synthesis of CPO-27-Ni in the presence of different ratios of benzoic acid and acetic acid as modulators. Yields, powder X-ray diffraction data, scanning electron microscopy results, and elemental, thermogravimetric, and gas sorption analyses are compared to study the influence of the modulator on the product. The results show that we have successfully synthesized pure CPO-27-Ni independent of the amount of modulator. The modulator affects the resulting morphology of the crystalline product with a defined variation of particle sizes and shapes. In addition, ESI-MS has been employed in probing the reaction solutions. It shows the preferred formation of complexes between the metal cation and the modulator, thus indicating that the ligand substitution plays a major role in the crystal growth