New MOF produces water from the air for Water Quality Month

Today marks the beginning of Water Quality Month, which focuses on, as the name implies, the quality of water. In many regions around the world, people do not have access to clean drinking water, and it is only becoming scarcer. Even if you don’t live nearby a lake, river, however, there is still a source of fresh water nearby: in the air. Researchers at MIT and the University of California at Berkeley developed a metal organic formwork (MOF) that has a sponge-like configuration and pulls water from even very dry air. The only source of energy it needs is a little heat, from the sun or otherwise.

According to the researchers, the new method has potential for widespread use in virtually any location, regardless of humidity levels. The system is a passive one, based on a foam-like MOF material that draws moisture into its pores. The material does not need any outside energy, only heat. This can come from the sun, but also, for instance, from a wood fire.

The key to the new system lies in the porous material itself. MOFs are sponge-like configurations with large internal surface areas. The chemical compositions of MOFs can be tweaked to make them hydrophilic (water-attracting).

When the material is placed between a black painted top surface, which absorbs solar heat, and a lower surface at the same temperature as the outside air, water is released from the pores as vapour. Naturally driven by the temperature and concentration difference, it drips down as liquid and collects on the cooler lower surface.

1 kilogram (2.2 pounds) of the material can collect 2.8 litres (5.9 liquid pint) from dry air with a humidity of just 20 per cent per day, which is more than enough for one person to drink.

MOFs can be tuned easily, which means that each material can be made suitable to different conditions, such as lower or higher humidity.

The present version can collect water up to about 25 per cent of its own weight, but with further tuning the researchers think that proportion could be at least doubled.

Other methods to collect water include fog-harvesting, which, as the name implies, requires fog, while methods to pull water from dry air are rather expensive. For more on water harvesting at Materia, click here and here.

Photos: MIT & University of California