May 17 2019
Metal-organic frameworks, or MOFs, are considered as versatile compounds whose crystal structure contains nano-sized pores.
EPFL chemical engineers have designed an easy method to achieve commercially attractive carbon-capturing with metal-organic frameworks. (Image credit: EPFL)
Due to their nanopores, MOFs are currently utilized in many different applications, such as mimicking DNA, isolating petrochemicals, and eliminating heavy metals, hydrogen, fluoride anions, and even gold from water.
Particularly, gas separation is of major interest to several industries, for example, purifying natural gas, enriching air in metal working, producing biogas, and recovering hydrogen from oil refineries and ammonia plants.
The flexible ‘lattice’ structure of metal-organic frameworks soaks up gas molecules that are even larger than its pore window making it difficult to carry out efficient membrane-based separation.
Kumar Varoon Agrawal, the GAZNAT Chair for Advanced Separations, EPFL Valais Wallis
Currently, researchers from Agrawal’s laboratory have considerably enhanced the gas separation by stiffening the lattice structure of the MOFs. The team achieved this feat with the help of an innovative technique called “post-synthetic rapid heat treatment,” in which a popular MOF known as ZIF-8 (zeolitic imidazolate framework 8) is baked for a few seconds at 360 °C.
This technique significantly enhanced the gas-separation performance of the ZIF-8—especially in “carbon capture,” a process that is capable of capturing the emissions of carbon dioxide generated from the use of fossil fuels, thus inhibiting it from penetrating the atmosphere.
For the first time, we have achieved commercially attractive dioxide sieving performance a MOF membrane.
Kumar Varoon Agrawal, the GAZNAT Chair for Advanced Separations, EPFL Valais Wallis
The researchers attribute this enhancement to a reduction of the lattice parameters which renders the MOF’s chemical bonds stiffer. The novel procedure did not have an impact on the bonding environment, the main chemical composition, and the crystallinity of the material.
Rapid heat treatment is an easy and versatile technique that can vastly improve the gas‐separation performance of the MOF membranes. By making the lattice rigid, we can efficiently carry out a number of separations.
Kumar Varoon Agrawal, the GAZNAT Chair for Advanced Separations, EPFL Valais Wallis
EPFL, ETH board, Swiss National Science Foundation (SNSF), and AP Energy grant funded the study.