Here’s one way to harvest water right out of the air Materials known as metal-organic frameworks, or MOFs, collect the moisture for drinking and other uses.
Materials known as metal-organic frameworks can harvest humidity from the air, even when that air is relatively dry.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. It just might slake the thirst of those living in remote or dry areas.
The new materials belong to a type known as metal-organic frameworks (MOFs). Their name provides clues about what they’re made from. Imagine a set of super-tiny Tinkertoys.
The hubs are small clusters of metal atoms. Chains of carbon-bearing compounds serve as the “sticks” linking those hubs together.
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.
There are even MOFs that could be used in tanks to store hydrogen for electricity-making fuel cells.
A system that used these would be lighter weight and safer to use, especially in vehicles._ But communities in arid parts of the world would be most interested in the MOFs that absorb water.
These can capture plenty just from the air, says Zhiyong Xia. This materials scientist works at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
Sign Up For the Latest from Science News for Students Weekly updates for inquiring minds of every age, delivered to your inbox. 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.
By absorbing humidity cool air (left) and then releasing it at higher temperature, materials called metal-organic frameworks (MOFs) can collect water without using much energy. M.W. LOGAN, S. LANGEVIN AND Z. XIA/SCIENTIFIC REPORTS, 2020 Promise and potential They investigated nine different MOFs that are able to harvest water.
The metal in some was zinc. Others were made using titanium, copper, chromium or zirconium. In the lab, the researchers placed samples of each in humid, room-temperature conditions for a full day.
Then, they heated the material in drier air to release the water that each had picked up. They repeated these cycles of soak-and-release at least 10 times.
Some MOFs didn’t pick up much water. Others soaked up a lot at first, but later released only a fraction of it. In later cycles, the material also might absorb much less than it initially did.
Explains Xia, that’s a sign such materials attracted water a little too well._ In the end, Xia reports, one zirconium-based MOF stood out. The test samples were always small, he notes.
But if the weight of that MOF sample had been 1 kilogram (2.2 pounds), the material would have absorbed and then released more than 8 liters (2.1 gallons) each day.
That beats any previous MOF-based water-collection system. Xia and his teammates described their findings January 30 in Scientific Reports.
Omar Yaghi is a materials scientist at the University of California, Berkeley. There’s a big difference between lab tests and field studies, he notes.
What’s more, he points out, “The challenge is not just to take up water from humid air, but to do it at low humidity, too.”
Harvesting water vapor from air with humidity levels of less than 50 percent “is very challenging,” Yaghi says. But in recent field tests, his team and others have shown that some MOFs show great promise in water harvesting, even in desert-like environments.
Specifically, they were able to recover water during tests in California’s Mojave (Moh-HAH-vee) Desert. They exposed their aluminum-based MOF to outdoor air with humidity as low as 10 percent.
Even in those very arid conditions, a kilogram of the MOF they used would have been able to collect 0.7 liters of water from the air. His team reported its achievement August 27, 2019 in ACS Central Science.
Need water but you have no access to rain, lakes or groundwater? Materials known as metal-organic frameworks could be used to slurp that water from the air, new data show.
This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.
Power Words More About Power Words arid: A description of dry areas of the world, where the climate brings too little rainfall or other precipitation to support much plant growth.atom: The basic unit of a chemical element.
Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
carbon: The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond.
It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
carbon dioxide: (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas).
Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere.
chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O.
Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds._ climate: The weather conditions that typically exist in one area, in general, or over a long period.
climate change: Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.
Colleague: Someone who works with another; a co-worker or team member.
component: Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).
compound: (often used as a synonym for chemical) A compound is a substance formed when two or more chemical elements unite (bond) in fixed proportions.
For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.
copper: A metallic chemical element in the same family as silver and gold. Because it is a good conductor of electricity, it is widely used in electronic devices.
engineer: A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
(v.) To perform these tasks, or the name for a person who performs such tasks._ environment: The sum of all of the things that exist around some organism or the process and the condition those things create.
Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
field: An area of study, as in: Her field of research was biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street.
It is the opposite of an artificial setting, such as a research laboratory.
filter: (in chemistry and environmental science) A device or system that allows some materials to pass through but not others, based on their size or some other feature.
fuel cell: A device that converts chemical energy into electrical energy. The most common fuel is hydrogen, which emits only water vapor as a byproduct.
green: (in chemistry and environmental science) An adjective to describe products and processes that will pose little or no harm to living things or the environment._ host: (in biology and medicine) The organism (or environment) in which some other thing resides.
Humans may be a temporary host for food-poisoning germs or other infective agents.
humidity: A measure of the amount of water vapor in the atmosphere.
(Air with a lot of water vapor in it is known as humid.)
hydrogen: The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable.
It’s an integral part of many fuels, fats and chemicals that make up living tissues. It’s made of a single proton (which serves as its nucleus) orbited by a single electron.
materials scientist: A researcher who studies how the atomic and molecular structure of a material is related to its overall properties.
Materials scientists can design new materials or analyze existing ones. Their analyses of a material’s overall properties (such as density, strength and melting point) can help engineers and other researchers select materials that are best suited to a new application.
metal: Something that conducts electricity well, tends to be shiny (reflective) and malleable (meaning it can be reshaped with heat and not too much force or pressure).
MOFs: Short for metal organic frameworks. These are carbon-based chemicals that contain clusters of metal atoms.
Those metal atoms can trap other compounds and chemically react with them.
molecule: An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound.
Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
oxygen: A gas that makes up about 21 percent of Earth’s atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).
physics: The scientific study of the nature and properties of matter and energy.
Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. A scientist who works in such areas is known as a physicist.
pore: A tiny hole in a surface. range: The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists.
toxic: Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity. trait: A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.
water vapor: Water in its gaseous state, capable of being suspended in the air._ wavelength: The distance between one peak and the next in a series of waves, or the distance between one trough and the next. It’s also one of the “yardsticks” used to measure radiation.
zirconium: A metallic element that is often used in structures needed to withstand high temperatures and radiation (such as nuclear reactors)._