Origami, the art of paper folding, has long been associated with child’s play and the creation of simple paper cranes. However, in recent years, origami has emerged as a captivating research topic in materials science. Scientists have discovered that origami-inspired materials can possess mechanical properties that are difficult to achieve in conventional materials. This has led to a growing interest in exploring origami tessellation at the molecular level.

In a groundbreaking study published in Nature Communications, a team of researchers from the Ulsan National Institute of Science and Technology has described the development of a two-dimensional porphyrinic metal-organic framework (MOF) based on origami tessellation. The MOF was self-assembled from zinc nodes and porphyrin linkers, showcasing folding motions reminiscent of origami.

The team combined theoretical modeling with experimental outcomes to understand the origami mechanisms underlying the 2D porphyrinic MOF. They discovered that the flexible linker within the MOF acted as a pivoting point, enabling the folding motions. This revelation unveiled the presence of origami mechanics at the molecular level, providing new insights into the behavior of these fascinating materials.

In their study, first author Eunji Jin and colleagues focused on developing a metal-organic framework based on double-corrugation surfaces of origami tessellation. They assembled the framework using a flexible porphyrin linker and a zinc paddlewheel secondary building unit. They observed unusual folding behaviors in the metal-organic framework attributed to origami mechanics through thermal movement experiments. These metal-organic frameworks based on origami tessellation hold great promise as an emerging class of mechanical metamaterials.

The research team also delved into the crystal structures of the developed metal-organic framework, PPF-301. They synthesized PPF-301 crystals with a zinc porphyrin component through a solvothermal reaction. These crystals exhibited a pale purple color and a rectangular plate shape. By analyzing the synchrotron powder X-ray diffraction pattern, the team confirmed the presence of the origami-based crystal structure. The mechanical properties of the PPF-301 metal-organic framework were also explored.

The research team conducted quantum mechanical calculations to optimize the structure and calculate the total electronic energies. By applying mechanical stress, they observed changes in dihedral and bond angles, influencing the material’s behavior. Previous studies have shown that flexible metal-organic frameworks can exhibit unique properties, such as negative linear compressibility and negative Poisson’s ratio. The PPF-301 material developed in this study showcased the origami movement and demonstrated its potential as a metamaterial.

In conclusion, Eunji Jin and her team have made significant strides in origami-inspired materials by developing a two-dimensional porphyrinic metal-organic framework based on origami tessellation. Their study sheds light on the origami mechanics underlying these materials at the molecular level. The discovery of origami-based crystal structures and the exploration of their thermal response and mechanical properties open up new possibilities for developing advanced metamaterials. With further research and development, origami metal-organic frameworks could find applications in various fields, including molecular quantum computing.

References

• Jeewandara, T. & Phys.org. (2023, December 7). Metamaterials and origamic metal-organic frameworks. Phys.Org; Phys.org. https://phys.org/news/2023-12-metamaterials-origamic-metal-organic-frameworks.html
• Jin, E., Lee, I. S., Yang, D. C., Moon, D., Nam, J., Cho, H., Kang, E., Lee, J., Noh, H.-J., Min, S. K., & Choe, W. (2023). Origamic metal-organic framework toward mechanical metamaterial. Nature Communications, 14(1), 7938. https://doi.org/10.1038/s41467-023-43647-8