Two-Faced Catalyst

Tandem reactions taking place at the interface between organic and aqueous layers in a biphasic solvent system can now be catalyzed by different parts of the same nanoparticle, thanks to a new design by Daniel E. Resasco and coworkers of the University of Oklahoma (Science 2010, 327, 68). The team started by creating MgO-based nanoparticles, which can serve as a basic catalyst. The researchers then grew carbon nanotubes on the MgO surface and adsorbed palladium onto the nanotubes. The MgO surface prefers to be in water, but the nanotubes prefer an organic solvent, thus the nanoparticles end up residing in and stabilizing the emulsion layer of a water/emulsion/decalin solvent system. Resasco and coworkers used the recyclable nanoparticles to develop a tandem reaction that is useful in biofuel production, where the reaction mixture typically has a complex composition. In the first step, MgO catalyzes coupling of 5-methylfurfural and acetone in the aqueous phase. The product slips into the organic phase where a subsequent Pd-catalyzed hydrogenation takes place.