Metal-Organic Frameworks (MOFs) are distinguished from conventional polymers by their unique structures featuring open internal spaces of specific sizes. This characteristic enables the selective passage of certain molecules while preventing others from entering. Additionally, the metal components within these frameworks facilitate intriguing chemical reactions, acting as catalysts or selectively binding to individual molecules in a mixture.
Initially, Robson faced skepticism at the University of Melbourne about the stability of the molecular structures he aimed to create. Most experts believed these newly conceived molecules would be prone to instability and collapse.
The inaugural MOF created by Robson utilized copper as the metallic element. This framework was connected to an organic molecule characterized by a rigid benzene ring, preventing any bending. Both the organic molecule and copper could form four distinct bonds, enabling the construction of the structure through a method akin to stacking three-sided pyramids—a design choice made deliberately by Robson.
Credit:
Johan Jarnestad/The Royal Swedish Academy of Sciences
During the initial stages, the internal cavities of the MOF remained filled with the solvent used for its formation, which was capable of moving freely throughout the structure. From this experimentation, Robson forecasted numerous attributes that have been incorporated into various MOFs since then. These include the capacity to maintain structural integrity after solvent removal, the existence of catalytic sites, and the function of MOFs as effective filters.
Broadening the Concept
While Robson’s early predictions may have seemed overly optimistic, his success is evidenced by the fact that he inspired confidence in other chemists regarding the potential of MOFs. One such scientist, Susumu Kitagawa from Kyoto University, along with his team, developed a MOF featuring extensive internal channels that spanned the entire length of the framework. This structure, created in an aqueous solution, could be dehydrated to allow gas to flow through it while effectively retaining molecules like oxygen, nitrogen, and methane.
