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Metal-Organic Frameworks

MOF sieves propylene from propane

Material features pockets that open to either propylene or propane, depending on pressure

by Bethany Halford
July 26, 2021 | A version of this story appeared in Volume 99, Issue 27


Metal-organic framework structure with a central channel and orthogonal pockets.
Credit: Adapted from Nature
This illustration of JNU-3a shows the MOF’s central channel in yellow and orthogonal pockets in teal. Gray = C, red = O, blue = N, purple = Co.

Although they differ by just two hydrogen atoms, propylene and propane have vastly different uses. Propylene is a valuable chemical feedstock for making polymers, like polypropylene, whereas propane is burned for heat and cooking. The two are usually found as a mixture, and separating them requires an expensive and energy-intensive distillation process. To save energy, scientists have explored using metal-organic frameworks (MOFs) to separate propylene from propane. Researchers at Jinan University now report a MOF that can sieve 99.5% pure propylene from a 50-50 mix of propylene and propane in a single pass (Nature 2021, DOI: 10.1038/s41586-021-03627-8). Chemists led by Weigang Lu and Dan Li invented the MOF, known as JNU-3a. It features a slim channel with a series of small, orthogonal pockets—like a long, straight hallway that has many rooms coming off it. These pockets are dynamic and will sequester either propylene or propane, depending on how much pressure the MOF is under. To separate the propylene and propane, the researchers flow the hydrocarbons through JNU-3a at 1 kPa of pressure. Propylene gets trapped in the pockets while propane flows through. The researchers then purge the MOF to get 99.5% pure propylene. JNU-3a can be readily recycled and reused by flowing helium through the material.


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