Metal-organic frameworks (MOF) are a new class of highly porous materials. They are compounds consisting of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures. A team of Clarkson University researchers has designed a new material, using a MOF, that uses light to capture carbon dioxide from exhaust gasses in the atmosphere.

MOFs are structured similarly to a jungle gym, where the nodes represent metal clusters, the struts are organic ligands, and the pores of the framework are accessible for guest molecules. One gram of a MOF can have the surface area of more than three football fields. Their spacious pores provide MOFs with the potential to be used as ‘sponges’ for storing gases such as hydrogen, carbon dioxide or natural gas. They could also be used as nano-sized sieves to purify gases or liquids, for catalysis, or for the targeted transport of drugs in the body.

Until now, the challenge was to design a material with a low energy requirement for an efficient capture and release process.

According to the researchers, the technology can be applied to the energy landscape, allowing for small-molecule separation of petroleum products and natural gas storage and purification. Once the carbon dioxide molecules are captured in the MOF, the molecules can be reused or put into storage.

The team’s research shows that reversible light-responsive behaviour creates on-off switchable charge gradients at the MOF’s major adsorption sites, allowing significant control of the gas sorption process while remaining energy efficient.

The team designed a material that can release the CO2 by irradiating the material with light, so there is no energy penalty anymore, as light is abundant.

Photo: Clarkson University