Materials chemist and data scientist Dr Chloe Coates’ lecture on “Order, disorder and ices: exploiting disorder in functional materials design” first introduced the use of ‘metal-organic frameworks’ (MOFs) in ‘carbon capture and storage’ (CCS). In this article, I will delve deeper into other applications of MOFs in the modern world, evaluating their potential for solving the water crisis that currently affects 29% of the world’s population.
What are MOFs?
Pioneered by Professor Omar Yaghi, MOFs are ordered lattices composed of metal ions or clusters joined by organic ‘linker’ molecules. The metal ions form nodes that bind the arms of the linkers together to form a repeating, cage-like structure with high porosity and surface area. Under specific conditions (such as temperature, pH, and pressure) research scientists can create different MOFs with various applications, using algorithms to accurately predict the mechanical properties of the hypothetical materials.
How can MOFs be used to harvest atmospheric water?
Gases differ in 2 main ways: polarizability and size. MOFs can be used to optimise gas storage by utilizing the size and polarizability of gas molecules. Programing the MOFs to specifically store water vapour can be achieved by either altering its pore size, hydrophobicity, or hydrophilicity.
The MOFs would be exposed to the saturated atmosphere overnight, allowing water molecules to enter its framework and remain in the interior. By concealing the system, this ensures that the water vapour is not transferred elsewhere, and shading areas of the harvester allows direct sunlight to heat the MOFs. Once the MOFs are heated, the water molecules are expelled out and condensed, allowing liquid water to be collected.
Water Harvesting Inc. is leading the development and implementation of this new sustainable, point-of-use drinking water source. Water Harvesting Inc. states that their “MOFs technology is specifically tailored for harvesting water from the atmosphere in relative humidity levels as low as 15%”. Professor Omar Yaghi believes that, if applied practically, MOFs will give promising results globally. He declares that “one-third of the world’s population lives in arid regions, yet the air there contains about 30% humidity”.
Are MOFs the way forward?
Increasing research and experimentation needs to be done before introducing this technology to water-stressed countries as a reliable source of drinking water. Whilst the self-assembly in the reaction mixture of MOFs can produce close to 100% product yield, challenges may arise during the design and construction of the system’s dimensions to support communities. Informing individuals about the maintenance of the system will also be important when this technology is put into practice. Investments into improving the efficiency of the technology (such as using aluminium-based MOFs) needs to be encouraged. It would be beneficial to consider the application of this technology in other fields of research, such as drug delivery and hydrogen storage.
Synthesising new materials could be essential for better supporting our ever-changing environment, and the most vulnerable in our society.
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