Cu2O Pseudomorphic Conversion to Cu Crystals for Diverse Nitroarene Reduction

Cu2O cubes, octahedra, and rhombic dodecahedra can be pseudomorphically converted to Cu crystals of the corresponding morphologies through the addition of ammonia borane. Nitroarene can be completely reduced during the compositional transformation with four equivalents of ammonia borane at 30 degrees C in 25 min. All the obtained polyhedral Cu crystals can give 100% nitroaniline conversion to p-phenylenediamine exclusively, but commercial Cu2O powder shows a comparatively lower 4-bromonitrobenzene conversion and yields a mixture of products. Use of sodium borohydride as a reducing agent resulted in the formation of deformed Cu particles and a low nitroaniline conversion percentage. Cu2O cubes cannot be converted to Cu particles with the addition of hydrazine, and nitroaniline conversion did not occur. Nitro group reduction is successful with high yields for diverse nitroarene molecules giving only a single product starting from a solution of the nitroarene compound, Cu2O cubes and ammonia borane.