Water Adsorption in Porous Metal-Organic Frameworks and Related Materials

Three criteria for achieving high performing porous materials for water adsorption have been identified. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. Water adsorption properties of 23 materials were investigated, 20 of which being metal-org. frameworks (MOFs). Among the MOFs were 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcryst. powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examd. for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)4(-CO2) secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl org. linkers to make extended porous frameworks. The permanent porosity of all 23 materials was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temp. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermol. interaction between adsorbed water mols. within the pores.

Publié dans:
Journal of the American Chemical Society, 136, 4369-4381

 Notice créée le 2017-02-23, modifiée le 2018-12-03

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