Amorphous Flowerlike Goethite FeOOH Hierarchical Supraparticles: Superior Capability for Catalytic Hydrogenation of Nitroaromatics in Water.

Fabrication of anilines from the corresponding nitroaromatics is a hot topic both for academia and for industry; however, conducting this protocol in water over a noble-metal-free catalytic system is still a great challenge. Continuous efforts are being made on exploiting novel catalysts for this transformation. In this work, we developed a scalable method for synthesizing the uniform flowerlike amorphous α-FeOOH hierarchical supraparticles. The well-defined amorphous α-FeOOH was prepared through an environmentally benign method, which is hydrolysis of the self-assembled iron glycolate at room temperature. Compared with other iron-only catalysts, this flowerlike amorphous α-FeOOH hierarchical supraparticle catalyst exhibits the best performance in the catalytic reduction of nitroaromatics to corresponding anilines by using water as the reaction solvent (turn over frequency is 106 h-1 for 4-nitrophenol in water). The further results indicated that the amorphous structure, special nanostructures, and adsorption-desorption synergy offered excellent activity. The kinetics study shows that the reduction of 4-nitrophenol is first order for α-FeOOH, and the apparent active energy Ea is 75.9 kJ mol-1. Furthermore, this catalyst can be used for eight times without obvious catalytic activity loss. We believe that this novel flowerlike amorphous α-FeOOH hierarchical supraparticle catalyst is a milestone in the reduction of nitro compounds.