Aerobic bacteria-supported biohybrid palladium catalysts for efficient cross-coupling reactions

Palladium-based catalysts are of key importance in organic synthesis due to their versatility and tolerance for a wide range of functional groups. However, they are challenged by increasing sustainability issues and complex preparation methods. Consequently, the development of new heterogeneous catalysts with enhanced sustainability is of significant interest. Typically, the synthesis of carbon supports for palladium is associated with high energy consumption or the generation of substantial chemical waste, prompting extensive research into the creation of sustainable biological supports. In this study, the potential use of aerobic bacterial cells as a support for palladium nanoparticles was explored, using Paracoccus yeei as a model organism. Electron microscopy, powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies demonstrated the formation of palladium particles on the cell surface as well as inside microorganisms following deposition from a solution. Control experiments established that bacterial cells do not interact with either the reactants or the products of selected cross-coupling processes. Furthermore, bacteria do not affect the analysis of reaction mixtures by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry (GC–MS). At the same time, palladium/Paracoccus yeei demonstrated efficient catalysis of the Mizoroki-Heck and Suzuki-Miyaura reactions, yielding results comparable to commercial palladium on carbon (Pd/C) catalysts. Employing a fresh start procedure and catalyst separation method, the catalyst was successfully recycled and reused across five cycles, maintaining good catalytic activity. In a broader aspect, bacteria-supported biohybrid palladium catalysts can represent a new type of catalysts worth to explore in a number of processes, where sustainability issues are concerned.