Fellows Seminar - Chemical reactions and sustainable recycling

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At this joint chemistry seminar, two USIAS projects will be presented. The three fellows involved, all from 2022 and who work in different areas of chemistry, will speak about their findings, and reflect on the implications and applications of their research.

Space-time journeys within inorganic chemical reactions

Benedikt Lassalle, Paris Cité University, France

Chemical reactions occupy a unique place in the transformation of matter within the biosphere and beyond. Whether they occur in natural or artificial processes, the formation or breaking of bonds is essential to life. Despite centuries of efforts to understand how chemical reactions proceed, we are still searching for tools to study their behaviour on short time scales. In particular, our knowledge of the synthesis of inorganic compounds that can be used as catalysts or photoabsorbing materials in energy conversion systems is incomplete. A detailed understanding of these processes would allow their widespread use in industrialized societies.

In this presentation, we will start by presenting some fundamental aspects of chemical reactions and the parameters that can be controlled to tune them. We will then describe spectroscopic methods, based on X-ray photons produced at synchrotrons, that can be used to follow chemical reactions under real-time conditions. These techniques allow for the analysis of the structure of reactants and/or products of a reaction with controlled parameters, which yield information on the mechanisms at play.

We will then showcase an application of this method to the study of hybrid organic-inorganic perovskites, whose synthesis remains poorly understood. These materials have been the focus of a lot of attention over the last decade, due to their intriguing properties in light absorption and conversion, and their potential application as photovoltaic materials.

Benedikt Lassalle’s USIAS project Microfluidics, X-rays and electrons: an integrated toolbox for the in situ study of hybrid perovskites synthesis was performed in collaboration with the team of Ovidiu Ersen at the IPCMS - Institute of Physics and Chemistry of Materials of Strasbourg (CNRS/University of Strasbourg).  

Turning plastic waste back into building blocks: a sustainable chemical recycling breakthrough

Jean-Baptiste Sortais, University of Toulouse III – Paul Sabatier, France & Éric Pollet, Institute of Chemistry and Processes for Energy, Environment and Health (ICPEES), University of Strasbourg and CNRS, France

Plastic waste has become one of our most pressing environmental challenges. Each year, millions of tons of plastic bottles, packaging, and textiles end up in landfills or polluting our environment. Traditional mechanical recycling methods gradually degrade plastic quality, limiting how many times materials can be reused. This research presents a promising solution: a chemical process that completely breaks down plastics back into their original building blocks, enabling true circular recycling.

Using a catalyst made from manganese - an abundant and inexpensive metal - we developed a method to chemically "unzip" various types of plastics under relatively mild conditions. The process works like running a chemical reaction in reverse: instead of joining small molecules together to make plastic, we use hydrogen gas to break the plastic chains apart, recovering the original small molecules (called monomers).

What makes this approach particularly practical is its robustness. We have successfully recycled real-world items - water bottles, food containers, clothing, even old CDs - without any cleaning or pre-treatment. The process handles coloured plastics, contaminated materials, and also complex products like cosmetic bottles. It works on multiple types of plastic, including PET (bottles and textiles), polycarbonates (CDs), and even polyurethanes.

This breakthrough offers genuine circularity: recovered monomers can be used to create new, high-quality plastics with properties identical to virgin materials. Unlike conventional recycling that produces lower-grade materials, this chemical approach prevents quality degradation, which potentially enables plastics to be recycled indefinitely while maintaining their valuable properties.

Read more about the two Fellows and their USIAS project: Reductive chemical recycling of polyurethanes via hydrogenation with homogeneous catalysts based on abundant transition metals.