Rods of multivariate MOFs (left) can be programmed with different metal atoms (colored balls) to perform a series of chemical tasks, such as controlled drug release, or to encode information like the ones and zeros in a digital computer. Image: UC Berkeley image by Omar Yaghi and Zhe Ji.Artificial molecules could one day form the information unit of a new type of computer or be the basis for programmable substances. Information would be encoded in the spatial arrangement of the individual atoms – similar to how the sequence of base pairs determines the information content of DNA, or sequences of zeros and ones form the memory of computers.
Researchers at the University of California (UC) Berkeley and Ruhr-Universität Bochum (RUB) in Germany have now taken a step towards this vision. As they report in a paper in Science, the researchers used atom probe tomography to read a complex spatial arrangement of metal ions in materials known as multivariate metal-organic frameworks (MOFs). These are crystalline porous networks of multi-metal nodes linked together by organic units to form a well-defined structure.
Recently, interest in characterizing metal sequences has grown because of the extensive information such multivariate structures would be able to offer. But to encode information using a sequence of metals, the metal arrangement first needs to be read, and this has proved to be extremely challenging.
Before this study, there was no method for reading the metal sequence in MOFs, but the researchers have now successfully done so using atom probe tomography, in which the RUB-based materials scientist Tong Li is an expert. For this, the researchers chose to use MOF-74, which was first made by Omar Yaghi and his group at UC Berkeley in 2005. They designed versions of this MOF with mixed combinations of cobalt, cadmium, lead and manganese, and then decrypted their spatial structure using APT.
In the future, this approach could allow MOFs to form the basis of programmable chemical molecules. For instance, a MOF could be programmed to introduce an active pharmaceutical ingredient into the body to target infected cells and then break down the active ingredient into harmless substances once it is no longer needed. Or MOFs could be programmed to release different drugs at different times.
"This is very powerful, because you are basically coding the behavior of molecules leaving the pores," Yaghi said.
These programmable MOFs could also be used to capture carbon dioxide and, at the same time, convert the carbon dioxide into a useful raw material for the chemical industry. "In the long term, such structures with programmed atomic sequences can completely change our way of thinking about material synthesis," write the authors. "The synthetic world could reach a whole new level of precision and sophistication that has previously been reserved for biology."
This story is adapted from material from the University of California, Berkeley, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.