A new structural discovery has a lot of potential for accessing advanced functional materials for environmental and energy purposes. Although cage-based porous materials, such as metal-organic polyhedra (MOPs), are gaining interest as a developing functional platform for a variety of applications, packing patterns that are rarely predictable and appear uncontrollable remain an unresolved issue.
Professor Wonyoung Choe (left) and Jiyeon Kim (right) in the Department of Chemistry at UNIST. Image Credit: Ulsan National Institute of Science and Technology.
A strategy for identifying and intelligently constructing new MOP structures is in high demand.
Professor Wonyoung Choe of the Department of Chemistry at the Ulsan National Institute of Science and Technology (UNIST) in South Korea led a research group that has made significant progress in exposing how upcoming MOP architectures can be anticipated and built at the molecular level. Their results are expected to usher in a new paradigm in the research and application of MOPs in materials.
Before MOPs, metal-organic frameworks (MOFs), another well-known family of porous material, evolved quickly. MOFs and MOPs have similar compositions (metal clusters and organic ligands). MOFs, on the other hand, have extended molecular building blocks, whereas MOPs have distinct cages made up of metal clusters and organic ligands that are packed together by weak interactions.
Thousands of MOFs have been synthesized since their invention, unlike MOPs, and they are currently becoming much more interesting components in research and industry. MOFs’ extraordinary success can be attributed to their predictable and designable architectures, as well as a wide range of molecular building components. The various architectures can be anticipated and built by examining the molecular geometry of building blocks.
Up until now, it was believed that strong bonds between building blocks were required to predictably create buildings. The rational design of MOPs has been less illuminated since weak or non-directional interactions frequently result in unanticipated topologies.
The researchers developed a unique sort of MOPs in which the design procedure can be used for molecular packing systems despite the absence of strong connections in this study. MOPs made of zirconium (Zr) are remarkable examples. Several weaker bonds can have a similar effect on the strong bonds, according to the authors.
With their exceptional chemical stability, Zr-based MOPs are an evolved version of MOPs. While Zr-MOPs are fundamentally cage-based compounds, they have properties similar to MOFs, such as a strong framework and everlasting porosity. According to the authors, such remarkable dual properties prompted them to examine the solid-state packing of Zr-MOPs further.
The study’s authors not only conducted a thorough examination of current structures but also identified future structures that have yet to be discovered but may be accessible. Controlling the packing structure, porosity and characteristics of cages requires a fundamental understanding of their nanoscale self-assembly.
The scientists predicted that Zr-MOPs’ unusual dual properties will result in plenty of new applications that are not possible with conventional MOPs or MOFs. They also encouraged researchers to look for other interesting cage-based framework classes.
The emergence of new structures would provide a new opportunity to control their properties. Taking a different perspective on cage-based frameworks can lead to a new stage of functional porous materials.
Wonyoung Choe, Professor, Department of Chemistry, Ulsan National Institute of Science and Technology
On March 10th, 2022, the results of the study were published as a perspective in Chem, a sister journal to Cell.
The National Research Foundation (NRF) of Korea provided support for this research through the Mid-Career Researcher Program, Hydrogen Energy Innovation Technology Development Project, Science Research Center (SRC), and Global Ph.D. Fellowship (GPF).
The Korea Environment Industry & Technology Institute (KEITI) was also involved through the Public Technology Program based on the Environmental Policy Program, which was funded by the Korea Ministry of Environment (MOE).
Journal Reference:
Kim, J., Choe, W., et al. (2022) Topology-guided roadmap for reticular chemistry of metal-organic polyhedra. Chem. doi.org/10.1016/j.chempr.2022.02.008.