Weak forces bind molecules to build rigid nanoporous frameworks
Doctoral student at the Nanochemistry Department, Max Planck Institute for Solid State Research (MPI-FKF), Germany
Master student (Furukawa Lab), at the time of this research.
Shun Tokuda
Shun Tokuda
Mr Shun Tokuda was a master’s student in the Furukawa Lab, studying the design and synthesis of novel porous materials based on metal-organic polyhedron (MOP) molecules. He focused on the intermolecular interactions among MOP molecules and discovered that strong van der Waals interactions between them can drive the assembly of a new type of porous framework material.
Please share with us the significance of your manuscript in terms of its research achievements, impact, or uniqueness.
In recent years, the chemistry of porous framework materials such as porous coordination polymers/metal-organic frameworks (PCPs/MOFs) and covalent organic frameworks (COFs) has been advancing rapidly. These materials are typically synthesized by linking molecular components into network-like structures, and their nanometer-sized frameworks are considered promising for a wide range of industrial applications. Among the key factors in their synthesis is the choice of chemical bonds, and it has been common practice to use strong bonds such as coordination or covalent bonds to connect the components.
The key result of this work is the discovery that van der Waals interactions—generally considered too weak to bind molecules—can be effectively utilized in the synthesis of porous frameworks through appropriate molecular design. Van der Waals forces between small molecules are indeed much weaker than typical covalent bonds. However, they become stronger as the contact area between molecules increases. For example, geckos are known to cling to vertical walls by maximizing this contact area. We applied this principle to the design of large molecules called metal-organic polyhedra (MOPs) and developed a new type of porous material, van der Waals open frameworks (WaaFs), by assembling MOP molecules into sparse network structures using strong van der Waals interactions. The resulting WaaFs showed excellent porosity and stability comparable to conventional materials. We also found that the material could be recycled by dissolution and recrystallization in case of degradation. These findings challenge the conventional assumption that strong chemical bonds are necessary for the synthesis of porous frameworks and they offer a general approach to controlling van der Waals forces, which has long been difficult. We hope this concept will inspire the development of a wide range of functional materials, beyond just MOPs or WaaFs.
Please tell us what was the most gratifying or inspiring moment for you during this research project.
I was very excited when I found that one of the samples showed unusual, incomprehensible behavior after synthesizing nearly 100 different materials. That sample was remarkably stable compared to the others and changed color reversibly before and after being placed in the measurement device. I immediately and intuitively knew it was a “special” material. That sample turned out to be WaaF-1, which we reportin this study.
Please tell us about the biggest challenge or problem you experienced while conducting your research. How did you overcome it?
I struggled quite a bit to clarify the significance of the study when summarizing the results into a paper. Van der Waals interaction is a very common phenomenon (which is exactly the point of the research), and the MOP molecule I used was just a modified version of one previously reported. So I sometimes lost sight of what I had really discovered. By carefully building up the logic through discussions with Professor Furukawa, I was eventually able to complete the paper in a way I was satisfied with.
Would you consider this work to be a turning point in your overall research direction? If so, how has your research direction changed as a result of this work?
Since this was my first first-author paper, I learned a lot about the depth of scientific writing. I realized that even (seemingly) ordinary experimental results can appear very different depending on how they are discussed in a paper. Moving forward, I hope to view my own research from broader perspectives and continue to pursue truly interesting work.
Please describe the current situation of your career. What is your current position? How has the knowledge and experience gained at iCeMS influencing your career?
I am currently a PhD student at the Max Planck Institute for Solid State Research (MPI-FKF) in Germany. While I was working at iCeMS, I really liked the diversity of people and the open atmosphere. This experience motivated me to pursue my doctoral studies outside of Japan. Although working with people who don’t share the same cultural background can be challenging at times, I find it very stimulating and rewarding.
Finally, please give a message or advice to young iCeMS researchers.
Even compared to my current institute, which is considered to be very well-equipped by global standards, I feel that iCeMS is a truly excellent place for research. There are many opportunities—both in terms of people and experimental facilities—so I encourage you to take on bold challenges and step outside your comfort zone!
Paper information
“Three-dimensional van der Waals open frameworks”
Authors: Shun Tokuda and Shuhei Furukawa
Published: March 2025