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

Abstract We report the high capacity of recycling of a technologically simple, easily recoverable, Ru@Fe₃O₄ magnetic nanocatalyst, efficient in the release of H₂ from ammonia‐borane (AB) solvolysis, using H₂O or methanol at room temperature (25 °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 μm). As nanocatalyst, this composite achieved short‐time (<10 min) AB full hydrolysis (3 equiv. H₂, no NH₃, [AB]=0.1 mol L⁻¹) with a turnover frequency (TOF) of ca 20 min⁻¹ (86 min⁻¹ at 50 °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 H₂ 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 H₂ release, achieved in a recycling process repeated over 8 cycles.