Ni2MnAl Heusler Alloy Nanoparticles for Chemoselective Hydrogenation of Nitro Compounds

Despite immense interest for years in Heusler alloys as magnetoelastic materials, their application in heterogeneous catalysis has only recently been explored. We report the development of highly active, robust and magnetically separable Ni2MnAl Heusler alloy nanoparticles as a heterogeneous catalyst for hydrogenation of aliphatic and aromatic nitro compounds to the corresponding amines. The easily synthesizable Ni2MnAl nanoparticles are thermally and chemically robust and exhibited excellent chemoselectivity in the hydrogenation of a range of aliphatic and aromatic nitroarenes, including those bearing functional groups sensitive to reduction, such as alkene, bromo, iodo, carbonyl and cyano, yielding the respective functionalized amines in good yields. Moreover, this solid catalyst is magnetically separable from the reaction mixture and could be recycled and reused at least 10 times without any loss in catalytic activity. The mechanism of the Ni2MnAl Heusler alloy nanoparticles catalyzed nitro reduction was studied by various spectroscopy, control experiments and kinetics. Our work opens a new avenue of developing heterogeneous earth-abundant metal catalysis for economic and environment-friendly synthesis of fine chemicals owing to straightforward synthesis and tunable composition of Heusler alloy nanoparticles from base-metal precursors and their diverse structure and properties in conjunction with their thermal and chemical stability, excellent chemoselectivity, magnetic separability and recyclability.