Kui Tan, a research scientist at The University of Texas at Dallas, has shown how a molecular cap can trap potentially harmful emissions within MOFs. Photo: University of Texas at Dallas.A team of researchers at The University of Texas at Dallas has developed a novel method for trapping potentially harmful gases within the highly porous materials known as metal organic frameworks (MOFs).
Made up of metal ion centers connected by organic linker molecules, MOFs naturally form a honeycomb-like structure that can trap gases within each comb, or pore. As such, they have the potential to trap the emissions produced by everything from coal-fired power stations to cars and trucks. Some molecules, however, are simply adsorbed too weakly to stay trapped for long within the MOF scaffolding.
"These structures have the ability to store gases, but some gases are too weakly bound and cannot be trapped for any substantial length of time," explained Kui Tan, a research scientist in the Department of Materials Science and Engineering at UT Dallas and lead author of a paper on this work in Nature Communications.
As a way to solve this problem, Tan decided to try introducing a molecule that can cap the outer surface of each MOF crystal in the same way bees seal their honeycombs with wax to keep the honey from spilling out. The molecule he chose was ethylenediamine (EDA), which naturally formed a monolayer over the MOF, effectively sealing the pores to trap gases such as carbon dioxide, sulfur dioxide and nitric oxide inside. This monolayer is less than 1nm in thickness, or less than half the size of a single strand of DNA.
To determine how much gas could be trapped inside the EDA-capped MOF structures, Tan and his team used a technique called time-resolved, in-situ infrared spectroscopy. This revealed that the EDA monolayer could trap carbon dioxide within a MOF for up to a day.
"Potential applications of this finding could include storage and release of hydrogen or natural gas to run your car, or in industrial uses where the frameworks could trap and separate dangerous gases to keep them from entering the atmosphere," Tan said.
As an added benefit, Tan found that mild exposure to water vapor would disrupt the monolayer, with the vapor penetrating the framework and fully releasing the entrapped vapors at room temperature. According to Tan, the combination of trapping and easy release offered by EDA opens up new options for managing gas emissions.
"The idea of using EDA as a cap came from Kui who proceeded to do an enormous amount of work to demonstrate this new concept, with critical theoretical input from our collaborators at Wake Forest University," said Yves Chabal, head of the materials science and engineering department in the Erik Jonsson School of Engineering and Computer Science at UT Dallas and senior author of the paper.
This story is adapted from material from the University of Texas at Dallas, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.