Electrocatalytic Cross-Coupling Reactions with Heterogeneous Single Atom Catalysts

Fine chemicals make up the largest portion of the global chemicals market with their revenues expected to grow to $220bn by 2024. Examples of important classes of fine chemicals, are pharmaceuticals, agrochemicals, flavours and fragrances and speciality materials (e.g., polymers). With the increasing attention on energy usage, environmental impact and safety, there is an urgent need to develop new, mild and efficient synthetic process for sustainable fine chemicals synthesis. There has been a remarkable renaissance of electrochemical catalysis, with researchers exploring how fine chemicals can be synthesised with using electrictricity as a reagent. These energy efficient, electricity-driven processes can be easily integrated with renewable energy sources and avoid the use of dangerous and toxic chemicals, which makes them a powerful green tool for chemical synthesis. However, at present, electrocatalytic methods typically utilise so called homogeneous catalytic systems, which requires transition metal catalysts, whereby all of the catalyst is fully dissolved in the reaction mixtures. These systems often suffer from high catalyst loadings due to their limited stability under the reaction conditions. Furthermore, the expensive homogeneous catalyst can only be used once due to the challenges associated with catalyst separation and recycling.

With the rapid growth of nanoscience, heterogeneous catalysts have been exploited to tackle the aforementioned problems. Although they are stable and conveniently recyclable, their overall catalytic efficiencies are usually inferior to their homogeneous counterparts. In recent years, a new class of heterogeneous catalysts, namely single-atom catalysts (SACs), which are emerging as a new frontier in catalysis science. In this case, the active metal centre of the catalyst exists as isolated single atoms, which are stabilized by the support material., SACs can serve as a bridge between homogeneous and heterogeneous catalysts with the possibility of integrating the merits of both types of catalysts such as high activity, selectivity, stability and reusability. Indeed, many breakthroughs in clean energy conversion reactions (e.g., oxygen reduction, hydrogen evolution, CO2 reduction) using SACs has been reported recently. These have demonstrated their great potential in electrochemical applications, but electrocatalytic fine chemical synthesis using SACs remains unexplored.

As the most frequently used class of reaction in pharmaceutical synthesis, the so called cross-coupling reactions were recognized in 2010 by the Nobel Prize in Chemistry. In this project, we will exploit the inherent properties of SACs to revolutionise fine chemical synthesis by creating completely new heterogeneous electrochemical cross-coupling reactions as proof-of-concept examples. Through newly forged collaborations with Prof. Yanqiang Huang from Dalian Institute of Chemical Physics (DICP, the birthplace of SACs concept), Prof. Karl Ryder (UoL) and MOF Technologies, novel nickel based SACs will be synthesized using metal organic frameworks (MOFs) as precursors, and the mechanisms of these SACs catalysed reactions will be studied using modern material characterization techniques This project is highly interdisciplinary and at the intersection of cutting-edge organic synthesis, electrochemistry, materials science and state-of-the-art heterogeneous catalysis. Success in the area will bring both economic and environmental benefits and enable the manufacture of fine chemicals, such as pharmaceuticals, to be prepared using more sustainable processes. The understanding of catalyst structure-performance relationships and reaction mechanisms will enable the design of new SACs systems, that can be exploited for a range of chemical reactions, broadening its impact.