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On the general water harvesting capability of metal-organic frameworks under well-defined climatic conditions

: Trapani, F.; Polyzoidis, Angelos; Löbbecke, Stefan; Piscopo, Calogero Giancarlo


Microporous and mesoporous materials 230 (2016), S.20-24
ISSN: 1387-1811
Fraunhofer ICT ()

The ability of some highly porous materials to adsorb and desorb water vapor under atmospheric conditions without the use of external power sources could become a promising methodology for the capture and release of water in arid or desert regions of the world.
Here, the use of some readily available metal-organic frameworks as water harvesting materials has been tested and compared with other porous materials. Water adsorption experiments were conducted at 25 °C and at a relative humidity (RH) of 40%, while the desorption process took place at 45 °C with a RH of 10%. These experimental conditions are in good accordance with the climatic conditions being present in the Sahara desert during the summer season.
In all experiments, UiO-66 derived MOFs showed the best water harvesting efficiency, releasing up to 89% of the adsorbed water at 45 °C and 99% at 60 °C. Though, the adsorption capacity of UiO-66 is noticeably lower than that of more hydrophilic materials such as the MOF compound HKUST-1 and the zeolite A3. The latter, however, are only able to release water when they are heated up to at least 60 °C.
Finally, the stability of the investigated MOFs after adsorption-desorption cycles have been confirmed through XRD and FT-IR analyses.