Tuning Pd-nanoparticle@MIL-101(Cr) Catalysts for Tandem Reductive Amination

The versatility of MOFs as highly porous Lewis acidic supports for precious metal nanoparticles has been exploited for one-pot tandem reductive amination catalysis. MIL-101(Cr) loaded with Pd nanoparticles ca. 3 nm in size at 0.2-1 wt% has been used to catalyse the reaction of 4'-fluoroacetophenone with benzylamine under 10 bar of H-2 to give the secondary amine, 4'-fluoro-alpha-methyl-N-phenylmethylbenzenemethanamine. For the highest Pd loading, major hydrogenolysis of the secondary amine occurs in a second tandem reaction, but by changing the ratio of Pd to Lewis acidic Cr3+ active sites it is possible to tune the catalytic selectivity to the desired 2 degrees amine product. An empirical kinetic analysis was performed to demonstrate this active site complementarity.