In most materials, atoms and molecules are packed tightly together, leaving little or no empty space between them. This year’s Nobel Prize in Chemistry has been awarded to three scientists who created novel materials in which atoms and molecules are linked in a way that leaves large, neatly arranged open spaces inside the molecular structure.These spaces are extremely useful for storing or trapping other substances, making these materials — called Metal-Organic Frameworks, or MOFs — highly valuable in many situations.The Nobel Prize in Chemistry, announced on Wednesday, recognises the work of Susumu Kitagawa, Richard Robson, and Omar Yaghi in creating these special molecular constructions, made by linking metal atoms with carbon-containing molecules.Different kinds of MOFs can be used for applications like harvesting water from desert air, capturing carbon dioxide, or storing toxic gases. The great utility of MOFs lies in their ability to temporarily hold other substances in the empty spaces they contain, like a foam or sponge is able to hold air or water, and release it when needed.“Thanks to the laureates’ work, chemists have been able to design tens of thousands of different MOFs, facilitating new chemical wonders,” the Nobel Prize committee said.FrameworksThe difference between most normal compounds and the MOFs is similar to that between a building with very tiny rooms and many solid brick walls and one comprising only pillars and beams and no walls. MOFs, thus, contain very large empty spaces confined within their molecular structures.It was Robson, teaching at the University of Melbourne in the 1970s, who first thought of the idea while engaged in the standard exercise of making classroom models of molecules using wooden spheres and sticks. He wondered if he could link the atoms, represented by spheres, with molecules instead of other atoms, and form new molecules.Story continues below this adHe took several years to try out his idea, but was indeed successful in creating new molecules that were spread out and could contain other substances in the empty spaces. Some of the first molecules he created were relatively unstable, and not of much use beyond being novel.But his idea did find a few other takers, notably Kitigawa — whom the Nobel Prize committee described as someone with the knack of trying out ‘the usefulness of useless’ — and sometime later, Omar Yaghi, a native of Jordan who had moved to the United States as a teenager for his studies.Working separately, they created many different MOFs, and slowly their utilities became evident.Special properties“There is no dearth of porous materials, either naturally occurring or created. Think of bread or biscuit, for example, or sponge. These can also hold water inside them. But there is an important difference between these and MOFs. In bread or biscuit molecules, the pores are randomly arranged. There is no control over where these spaces would occur, or how much water they would absorb. The beauty of MOFs is that they can be customised to a very fine detail. And that is why they can be tailor-made for specific purposes,” said Rahul Banerjee, a professor of Chemistry at the Indian Institute of Science Education and Research (IISER) Kolkata.Story continues below this adBanerjee added that with MOFs, everything can be pre-designed, from the kind of material it would absorb or store, the shape and size of the empty space needed for that, and the chemistry of the MOF that would achieve the goal. “One of the most sought-after uses of MOFs these days is to try and capture carbon dioxide from the atmosphere. This is very important from the climate change perspective. These MOFs can selectively attract CO2 molecules from the air, ignoring others,” Banerjee, who did his post-doctoral research with Omar Yaghi, and works in precisely the same area now, a branch of chemistry called reticular chemistry, said.He said it was this versatility of MOFs that was getting acknowledged through the Nobel Prize. “The work on MOFs is now four decades old. But it is being used for a very wide variety of purposes now. The technique is extremely versatile and very useful. I hope this Nobel Prize draws the attention of the government and the private sector towards research in this field in India as well,” he said.