Gas separation is crucial across many industries but often involves energy-intensive processes, such as cooling gases to liquefy and then separate them based on their evaporation temperatures. However, Professor Wei Zhang and his team at the University of Colorado Boulder have developed a new type of porous material that is flexible, sustainable, and energy-efficient. This material can adjust its pore sizes at different temperatures to selectively allow certain gases to pass through, potentially revolutionizing the way gases are separated and reducing the overall energy required for these processes.
A new porous material allows for efficient, low-energy gas separation and is scalable for industrial use, offering a sustainable alternative to traditional methods.
Separating gases plays a crucial role in various industries, from medical applications, where nitrogen and oxygen are separated from air, to environmental processes like carbon capture, where carbon dioxide is isolated from other gases, and the purification of natural gas by removing impurities.
Separating gases, however, can be both energy-intensive and expensive. “For example, when separating oxygen and nitrogen, you need to cool the air to very low temperatures until they liquefy. Then, by slowly increasing the temperature, the gases will evaporate at different points, allowing one to become a gas again and separate out,” explains Wei Zhang, a University of Colorado Boulder professor of chemistry and chair of the Department of Chemistry. “It’s very energy intensive and costly.”
Much gas separation relies on porous materials through which gases pass and are separated. This, too, has long presented a problem, because these porous materials generally are specific to the types of gases being separated. Try sending any other types of gas through them and they don’t work.
However, in research published today in the journal Science, Zhang and his co-researchers detail a new type of porous material that can accommodate and separate many different gases and is made from common, readily available materials. Further, it combines rigidity and flexibility in a way that allows size-based gas separation to happen at a greatly decreased energy cost.
“We are trying to make technology better,” Zhang says, “and improve it in a way that’s scalable and sustainable.”
Adding flexibility
For a long time, the porous materials used in gas separation have been rigid and affinity-based—specific to the types of gases being separated. The rigidity allows the pores to be well-defined and helps direct the gases in separating, but also limits the number of gases that can pass through because of varying molecule sizes.
For several years, Zhang and his research group worked to develop a porous material that introduces an element of flexibility to a linking node in an otherwise rigid porous material. That flexibility allows the molecular linkers to oscillate, or move back and forth at a regular speed, changing the accessible pore size in the material and allowing it to be adapted to multiple gases.
“We found that at room temperature, the pore is relatively the largest and the flexible linker barely moves, so most gases can get in,” Zhang says. “When we increase the temperature from room temperature to about 50 degrees (DOI: 10.1126/science.adj8791
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