Coupling Molecular and Nanoparticle Catalysts on Single Metal-Organic Framework Microcrystals for the Tandem Reaction of H2O2 Generation and Selective Alkene Oxidation

A molecular catalyst, (sal)Mo-VI, and a heterogeneous catalyst, either Pd or Au nanoparticles (NPs), were integrated into one UiO-66 MOF microcrystal. The resulting dually functionalized catalysts, Pd@UiO-66-(sal)Mo and Au/UiO-66-(sal)Mo, have been utilized for a one-pot tandem reaction of H2O2 generation and selective liquid-phase alkene oxidation. The NPs serve as catalysts for the production of H2O2 from H-2 and O-2 gases, while the (sal)Mo moieties function as the oxidation catalyst. When the metal NPs are fully encapsulated within the MOF microcrystals, the alkene hydrogenation side reaction is largely suppressed, with a 6-fold decrease in the hydrogenation/oxidation product ratio for 5-bromo-1-cyclooctene favoring the epoxide as the major product. For Au/UiO-66-(sal)Mo, where the two catalysts are in close proximity on the MOF microcrystal, the enhancement in oxidation productivity is increased by 10 times in comparison to the [Au/UiO-66-NR2 + UiO-66-sal(Mo)] physical mixture of the two singly functionalized MOFs.