High Recyclability Magnetic Iron Oxide‐Supported Ruthenium Nanocatalyst for H2 Release from Ammonia‐Borane Solvolysis

We report the high capacity of recycling of a technologically simple, easily recoverable, Ru@Fe3O4 magnetic nanocatalyst, efficient in the release of H-2 from ammonia-borane (AB) solvolysis, using H2O or methanol at room temperature (25 degrees C). The initially oxidized Ru small nanoparticles (2-4 nm) are well-dispersed on an iron oxide support (i. e. super paramagnetic iron oxide of spinel structure, SPIO, as aggregates of 20 nm to a few mu m). As nanocatalyst, this composite achieved short-time (<10 min) AB full hydrolysis (3 equiv. H-2, no NH3, [AB]=0.1 mol L-1) with a turnover frequency (TOF) of ca 20 min(-1) (86 min(-1) at 50 degrees C). The post-catalysis characterization of the composite showed the formation of well-defined crystalline hcp Ru(0) dispersed on the SPIO. The activity for full H-2 release from AB is conserved over ten cycles, which is among the most effective recycling processes reported to date (a magnetic recycling is achieved in <2 min). Pleasingly, an even superior activity was found in the more challenging AB methanolysis, with a TOF up to ca 30 min(-1) for full H-2 release, achieved in a recycling process repeated over 8 cycles.