Sep 16, 2025

Molecular rotors could redefine memory storage

Researchers design heat-resistant COFs with molecular rotors, laying the groundwork for memory devices that surpass the limits of today's semiconductor technology.

(Nanowerk News) The race to pack more data into smaller spaces has pushed scientists to rethink the very materials that store information. Traditional semiconductors are nearing their limits, and researchers are turning to molecular technology for answers.

Among the most promising candidates are “molecular machines,” tiny systems where molecules behave like moving parts. Within this field, “molecular rotors” stand out. These are molecules that can rotate around chemical bonds, and if harnessed, they could enable memory devices far denser and more efficient than today’s chips.

The obstacle has been meeting three strict requirements: rotors must respond to electric fields, remain stable at room temperature, and still have enough space to rotate inside solid materials without being blocked by their neighbors. On top of this, any material must survive the heat generated by modern computing components.

A research team at the Institute of Science Tokyo has now achieved all of these feats. In a paper in the Journal of the American Chemical Society ("sln-Topological Covalent Organic Frameworks with Shape Dimorphism and Dipolar Rotors"), they describe a new class of covalent organic frameworks (COFs)—crystalline materials made from repeating molecular units—that give rotors both stability and freedom. Their design also withstands extreme heat, up to nearly 400°C.

The building block molecules, network formation by covalent bonds, shape dimorphism, scanning electron microscope images, and sln topology of the COFs developed (TK-COF-P and TK-COF-M). (Image: Institute of Science Tokyo) (click on image to enlarge)

The breakthrough came from combining a tetrahedral molecule with a newly designed three-armed molecule carrying dipolar rotors. Earlier versions worked in solution but failed as solids, where tightly packed molecules prevented rotor motion. The new COFs, however, formed an unusual “sln topology” structure with inherently low density. This open framework provided enough room for rotors to flip when triggered by heat or an electric field, while keeping them locked at ambient conditions.

The researchers also discovered that their COFs could grow into two distinct shapes—a hexagonal prism or a thin membrane—depending on the solvent used, revealing a previously unseen phenomenon in COFs known as shape dimorphism.

“Our COFs are a rare solid in which dipolar rotors can flip when stimulated but stay fixed at room temperature,” said project leader Professor Yoichi Murakami. “This demonstrates the potential of molecular machines for next-generation memory devices.”

Beyond creating a durable platform for molecular memories, the work expands the structural diversity of COFs, pointing to new directions in molecular design.

Source: Institute of Science Tokyo (Note: Content may be edited for style and length)