Contemporary chemistry is faced with a dual challenge : to meet ever-growing industrial needs and limit its environmental impact. This shift towards more environmentally-friendly practices is accompanied by a reconsideration of the history of organic chemistry, which has always depended on petroleum derivatives. Silicon, a simpler chemical element to exploit, could open the way to a more virtuous scientific and industrial practice.
Interview with Vincent Corcé*, chemist at the Collège de France.
The idea of a " more sustainable chemistry " has become a cross-cutting imperative, at the crossroads of scientific policies, environmental injunctions and social expectations. For chemist Vincent Corcé, this means " carrying out chemical transformations using more eco-compatible, environmentally-friendly methods ". This project begins with a critique of the historical foundations of organic chemistry, long dependent on petroleum derivatives as raw materials, solvents and reagents. To this dependence must be added that of noble metals (ruthenium, palladium, iridium), omnipresent in chemical processes, but costly, rare and ecologically problematic. As a result, there is an urgent need to explore alternatives. " We're trying to get away from this logic, to start from this scarcity and find alternatives ", says Vincent Corcé.
Even the more abundant transition metals (nickel, copper, cobalt) remain difficult to extract on a large scale without heavy environmental impact. What's more, international trade tensions make their supply more delicate.
The researcher underlines the importance of this shift for the discipline : " Organic chemistry still has the image of a highly polluting field, and it is crucial to change practices in order to modify the general public's perception ". In this context, the challenge of sustainable chemistry lies not only in the substitution of these resources, but also in a change of perspective. " What we're looking to do is no longer just produce molecules, but develop ways of recovering waste, recycling or inactivating harmful compounds ". Certain elements, such as silicon, offer chemical characteristics that are ideally suited to meeting tomorrow's challenges.
Silicon's alternative chemistry
Silicon is a strategic element in this reconfiguration. Abundant on Earth - notably in sand -, relatively inexpensive and chemically versatile, it has several properties that make it a potential substitute for certain functions traditionally performed by rare metals. As Vincent Corcé reminds us, " silicon is located just below carbon on the periodic table, with some similarities, as they belong to the same group, but also some notable differences ". This potential is being exploited in the development of so-called silylated catalysts, whose aim is to induce selective chemical reactions by activating bonds. Unlike highly reactive catalysts, which can only be manipulated under specific conditions (inert atmosphere, cryogenics), the structures developed by Vincent Corcé aim to be operational under milder, more robust conditions, and therefore more compatible with industrial implementation.
Its electronic affinity with elements such as oxygen and fluorine makes it particularly well suited to the activation of certain stable chemical bonds. " Our silyl derivatives fulfill this function, enabling us to activate, for example, a stable bond such as the carbon-oxygen bond, or even a very stable bond such as the carbon-fluorine bond ", explains the researcher. A salutary property at a time when the issue of eternal pollutants is becoming increasingly worrying.
The environmental challenge of PFAS
One of the major challenges facing the chemical industry today is the management of perfluoroalkylates, better known by the acronym PFAS, extremely stable substances that are ubiquitous in the environment. Used for their hydrophobic properties and heat resistance in textiles, food packaging and fire-fighting foams, these molecules persist in natural environments and are increasingly toxic. " The problem is that PFAS do not degrade. In nature, they accumulate everywhere, even in the drinking water of certain regions. Levels exceed regulatory thresholds ", warns Vincent Corcé. Their omnipresence in water, soil and even the human body makes them a major health and environmental issue.
Faced with the inefficiency of conventional treatment methods - pyrolysis of PFAS requiring temperatures in excess of 1000 °C - the team in which the researcher works is developing an alternative approach based on silicon catalysis. The aim is to activate the carbon-fluorine bond, one of the most stable in organic chemistry, to enable it to be broken under controlled conditions. " If we can rip out the fluorines that make up PFAS, then we can create something much less dangerous and much more treatable ", he explains. This switch from a persistent substance to a recyclable molecule is part of a logic of circularity. " The idea is not to destroy them, but to recycle them. These elements remain a source of carbon that can be valorized ", he adds.
This work opens up far-reaching prospects. It also testifies to a shift in the very aims of chemistry. Not just to produce, but to repair, to recycle, to make the transformation of matter compatible with the demands of sustainability. Silicon chemistry, in the perspective outlined by Vincent Corcé, is not content with offering a one-off substitute for existing practices, it is initiating a genuine redeployment of the disciplinary field, where catalysis becomes a tool for environmental management and molecular transformation a lever for sustainability. By focusing on issues such as the treatment of PFAS, this research shows a chemistry that cares about its consequences. In this context, silicon catalysis appears as a tool with a new scientific horizon.
*Vincent Corcé is a research chemist in Prof. Louis Fensterbank's Activations in Molecular Chemistry chair. The research project Silylated Lewis SuperAcids: from carbon-fluorine bond activation to PFAS recycling is funded by the Avenir Commun Durable initiative.
