Green Chemistry and Metal-Free catalysis

     

    Catalysis : at the core of sustainable development

    Catalysts play a central role in most chemical processes, from petrochemistry to drug synthesis, by reducing the energy consumption and amount of chemical wastes produced while increasing the selectivity and the yield of chemical reactions. Catalysis is at the core of green chemistry and sustainable development.  

     

     A change of paradigm in catalysis

    Although catalysis is a sustainable process, most catalysts are not. The most potent catalysts use noble metals like rhodium, iridium and platinum, which are costly and polluting to produce. For instance, a mile-depth hole must be dug and 10 tons of earth extracted to isolate 30 g of platinum! In addition, noble metals are highly toxic to plants and animals. Therefore, they must be removed from pharmaceutical products which can be costly.

     

     

    The use of these metals as catalysts was  considered for a long time a necessary evil until a new paradigm in chemistry appeared: metal-free catalysis. The discovery of Frustrated Lewis Pairs by Douglas W. Stephan has played an important role in this change of paradigm. A Lewis pair is composed of a Lewis acid, an electron-poor species, and a Lewis base, an electron-rich species. Traditionally, when a Lewis base and a Lewis acid meet, they will interact by forming a chemical bond. However, when steric or geometric constraints are introduced, strong bond formation is disfavoured leading to a “frustrated” character. This frustration induces important changes in the properties of these elements, leading to the activation of inert chemical bonds, which is the first step to efficient catalysis.   

    Our group has been interested in investigating the interactions between Lewis acids and bases for some time. We hope to use the chemistry of Frustrated Lewis Pairs and ambiphilic molecules in order to develop green and sustainable chemical processes that are also economically viable. Using our knowledge of transition metal chemistry, computational simulations and predictions, and some chemical insights, we are looking at the design of molecules having the desired catalytic activity.

     

    From European Journal of Inorganic Chemistry, Volume 2008, Issue 35. 
    Artwork by Marie Tremblay

    CO2 valorisation 

    Many industrial and energetic alternatives exist to reduce our fossil fuel consumption. However, they tend to be costly, their implementation is slow and some of these processes still have important environmental drawbacks. Our vision on this issue can be summarized in one concept: methanol economy. The methanol economy consists in replacing fossil fuels by “green” methanol. Green methanol can be produced by the hydrogenation of CO2 generated by industrial sources allowing that hydrogen is produced by water electrolysis using green energy, such as hydroelectric power.

    In comparison to hydrogen, methanol is an energy vector easy to transport and to use. Methanol can also be easily transformed into ethylene and other molecules at the core of many petrochemical processes. The synthesis of such as an energy vector from atmospheric CO2 can be compared to the fixation of CO2 by plants for the production of biofuels without the need of arable lands, fertilizers, in a more rapid and efficient way.

     

    Published in JACS : 2013, 2014

    Published in ACS Catalysis  

    Carbon-hydrogen (C-H) bonds activation

    Functionalization of C-H bonds is a very important catalytic process allowing the generation of high-value molecules by cleaving the omnipresent C-H bonds of organic precursors and replacing the hydrogen by interesting functional groups. In that regard, we recently demonstrated that FLP catalysts can catalyze the borylation of heteroaromatic C-H bonds. We are currently looking at catalyst optimization, with a focus on activating molecules of interest for the pharmaceutical and organic electronic industries, and at more transformations of interest in organic chemistry.

     

    Published in Science 

    Published in Chemical Communications

    Interview in Québec Science

     

    Rare earth elements extraction from industrial waste  

    In collaboration with Larivière and Kleitz groups, we are working on the synthesis of hybrid materials useful for the extraction and purification of rare earth elements from industrial wastes such as red mud. Rare earth elements are 17 elements of the periodic table including the 14 lanthanides. These atoms are essential components of many modern technologies (computers, cellphones, wind turbines, medical imaging, etc.). Unfortunately, the extraction and the purification of these elements is a very polluting process preventing many countries from developing such industry, despite the economic advantages. Our goal is to develop a method to isolate these products in a sustainable and profitable manner.    

     

    Entrevue dans Québec Science