As science and chemistry develop, new innovations emerge to fill our need for tools to achieve new developments. Which, in this case, is a class of materials called metal-organic frameworks that were initially found in the 90s, and which now gained attention with new research regarding its potential to be used as a catalyst in breaking down plastic.
Metal-organic frameworks, or MOFs for short, are compounds made of linkers -organic ligands- and positively charged metal ions to form one to three-dimensional structures. The metal ions and linkers form a cage-like three-dimensional material. This is done by heating the solvent for some time until it settles into the MOF structure. These materials are very significant because of their porous feature, along with their repeating and cage-like nature. These features allow the metal-organic frameworks to be versatile and create multiple opportunities for their usage. Moreover, the countless combinations of the metals and solvents allow MOFs to be adapted and utilized in many fields, which we cannot observe in most crystalline porous materials.
The nanoporosity of MOFs allows even a small amount of MOF material to encompass thousands of times more area than itself, if not more. Thus, the materials themselves actually exist in mostly empty spaces, proving the materials’ light nature. With their enormous internal surface area, they can be utilized in many areas of science.
With the selection of various metals and organic linkers, MOFs can be used for many purposes: catalysis, energy and gas storage, liquid and gas separation, biomedicine, etc. along with being processed into porous fabrics, glass, flexible thin films, and biocompatible membranes.
As we are all aware, plastic takes such long periods of time to break down in nature. In this case, a type of MOF works as a catalyst. Catalysts are used to speed up chemical reactions or able to reduce the pressure and temperature the chemical reaction requires in order to take place.
Recent research from Northwestern University demonstrated that MOF can be used as a catalyst to break down polyester-based plastic into its component parts, including terephthalic acid. Terephthalic acid is an acid that works as a building block in the creation of plastic. Thus, with this development, plastic waste can be broken down to create new plastic and turn it into a cycle instead of continuing to abandon countless kilos of plastic being discarded every day. This issue also cuts the manufacturing of plastic short as well. Plastic is a derivation of fossil fuels produced from oil. Plastic needs to be separated and refined to be turned into the water bottles we hold in our hands, plastic bags we use, plastic gloves we put on, and so much more. Metal-organic frameworks can not only cut this process short, but they also provide a new perspective, since fossil fuels are not limitless. And they might have been the recycling loop we were looking for.
And apparently, according to the aforementioned research, zirconium-based MOF as a catalyst was not only inexpensive but the catalyst’s efficiency also was not negatively impacted by the selection of the plastic.
All in all, although metal-organic frameworks are really light, just like their surface area, the fields they encompass are incredibly varied. It all depends on how we will be able to use them to our advantage.