Researchers at the University of Tsukuba have discovered a phenomenon—applying pressure to a copper-chromium Prussian blue analog, which is a compound featuring crystal voids, causes the discharge of water retained within these voids. This material is expected to serve as a novel onsite water production platform for the extraction of water solely through pressure application, without temperature or humidity control, even in arid regions.
Copper-chromium Prussian blue analogs are crystalline compounds containing voids (pores). The researchers found that the water retained in these pores can be expelled by applying pressure to these crystals. Previously reported onsite water production technologies rely on variations in temperature and humidity, and are thus strongly dependent on changes in environmental conditions, thereby often involving long waiting periods.
This material is expected to serve as a novel onsite water production platform for the extraction of water solely through pressure application, without temperature or humidity control, even in arid regions.
In this study, published in the Journal of Materials Chemistry A, the application of 1 GPa of pressure to a copper-chromium Prussian blue analog resulted in the expulsion of water stored in the crystal's pores, leading to the formation of droplets visible to the naked eye. The researchers also determined that approximately 240 g of water could be obtained per 1 kg of the crystal.
Infrared spectroscopy, X-ray absorption, and fluorescence spectroscopy measurements, performed before and after pressurization, revealed changes in the electronic states of both the water molecules and copper within the pores of the crystal. These findings show that pressure alters the originally hydrophilic pores into hydrophobic ones, thereby providing insights into the water-discharge mechanism.
This achievement is anticipated to the advancement of pressure-induced onsite water production technologies for use in arid and other harsh environments as well as provides a new perspective for developing water resource reuse technologies.