Watching energy materials as they form

Optimising synthesis processes

This has also been the case for COFs where several molecular components have to find the correct place during synthesis. Only then does the desired porous framework form over large areas. “Finding out why synthesis only works under certain conditions and not under others has intrigued me since my master’s days. Our approach in this project was to use the tools of physics to support chemists in their work. We wanted to shed more light on the complex synthesis processes and thus optimize them,” explains Christoph Gruber, who is researching this topic in Cortés’s team as part of his doctoral dissertation. To this end, the two scientists turned to the research group of LMU chemist Prof. Dana Medina, who is specialized in the synthesis of COFs, to establish a collaboration.

For the film shoot with the molecular stars, Gruber used a special microscope. With this tool, the team managed to follow the formation mechanism of the COFs at the nano level. The LMU researchers recently published their groundbreaking results in the journal Nature, accompanied by a video showing the processes that occur during synthesis in real time.

Early order is critical

Synthesis of the molecular frameworks demands one thing above all: precise control of the reaction and self-assembly of the molecular building blocks present. “Only when you have this control it is probable to obtain a highly crystalline structure with an extensive order and, ultimately, the desired functionality,” says Medina. “However, our knowledge particularly of the early stages of nucleation and growth is full of gaps. And this has thwarted the development of effective synthesis protocols. We therefore were extremely intrigued to visualize the reaction as it unfolds and set the focus on the earliest stages when the mixed molecular components are starting to react.”

This is precisely where Gruber started with his investigations, choosing what would seem at first glance to be an unconventional method to cast light on the opening scene of COF formation: iSCAT microscopy. The abbreviation stands for interferometric scattering, and biophysicists often use this technology to investigate things like the interaction of proteins. “The measurement principle is based on the fact that even the tiniest of particles, made up of just a few molecules, scatter incident light. If these scattered light waves overlap, we get interference – just like water waves in a pool. That is to say, we get larger and smaller waves depending on how the waves overlap. We record these light patterns with a high-resolution camera and, with subsequent image processing, we obtain pictures that reveal, for example, nano-scale COF particles,” explains Gruber. And here’s the kicker: the iSCAT method is suitable for capturing dynamic processes and thus for real-time measurements. This allows the researchers to watch the synthesis live, as it were.

Imagine trying to film tiny lava flows during a volcanic eruption.

Prof. Emiliano Cortés

Journal: Nature
DOI: 10.1038/s41586-024-07483-0
Method of Research: Experimental study
Subject of Research: Not applicable
Article Title: Early stages of covalent organic framework formation imaged in operando
Article Publication Date: 5-Jun-2024