An Investigation on the Production of Water-Stable, Porous Metal-Organic Materials

Abstract

Two mechanisms of increasing the water and structural stability of metal-organic frameworks (MOFs) were investigated. Two carboxylate MOFs, Mg-MOF-74 and HKUST-1, were post-synthetically modified with silica to increase structural stability while retaining the originally high zero-loading heats of adsorption, 65.4 kJ/mol and 32.2 kJ/mol, respectively. The modified materials were characterized by NMR, IR, SEM/EDX, PXRD, TGA, and adsorption of CO2 and N2. The silicated HKUST-1 showed remarkably high water stability, whereas the silicated Mg-MOF-74 did not. A second approach to stability was investigated using a novel phosphonate ligand, 2,7-bis(ethylphosphono)fluorene, yielding hollow microspheres upon hydrothermal reaction with cobalt (II) nitrate. The microspheres were thermally stable to 450°C, and were stable to sonication in water. The mechanism of formation, structure and chemical stability were investigated and will be discussed.