Harvest Water from Air !!!

Materials known as metal-organic frameworks, or MOFs, collect the moisture for drinking and other uses 

 

Water is something we cannot do without. People need it to grow crops and for a host of industrial processes. But we especially need it to drink. The body can’t survive more than three days or so without a drink of water. Now, researchers have developed materials that can pull water right out of thin air.

The new materials belong to a type known as metal-organic frameworks (MOFs). Imagine a set of super-tiny Tinkertoys. The hubs are small clusters of metal atoms. When these components join up, they create an open, honeycomb-like structure. 

MOFs have a range of useful traits. Last year, engineers reported getting green plants to take up the building blocks of MOFs and then assemble them internally. These MOFs were able to absorb harmful wavelengths of light so that they didn’t injure the plants. Other MOFs can filter toxic chemicals from the air and then store them or help break them down. Some can pull carbon dioxide from industrial smokestacks, which would help fight climate change. 

Water molecules (H₂O) are the perfect size and shape to pass through pores in the new MOFs. That lets them soak into the material. They have a second trait that’s just as important. Their internal arrangement of electrical charges attracts water. 

A water molecule is somewhat V-shaped. A negatively charged oxygen atom sits at the bottom of that “V,” explains Xia. At the V’s upper tips sit two positively charged hydrogen atoms.

But not all water-collecting MOFs are equally useful, notes Xia. Some attract and latch onto water molecules too well. Later, you’d need a lot of energy to release any water collected by them. His solution: Identify a MOF that doesn’t hold onto water molecules so aggressively.

Now he and his colleagues have done just that.