Selective and Efficient Reduction of Nitrobenzene to Aniline catalyzed by AuNPs Embedded in a Nanoporous Crystalline Polymeric Support

Congresso Divisione Chimica Industriale Salerno, Settembre 2015 Selective and Efficient Reduction of Nitrobenzene to Aniline catalyzed by AuNPs Embedded in a Nanoporous Crystalline Polymeric Support Annarita Noschese1*, Antonio Buonerba1, Carmine Capacchione1, Stefano Milione1, Alfonso Grassi1 1 - Dipartimento di Chimica e Biologia, Università degli Studi di Salerno, Via Giovanni Paolo II - 84084 Fisciano (SA), Italy, and CIRCC-Bari, Italy Abstract Supported Gold Nanoparticles (AuNPs) efficiently catalyze both oxidation and reduction reactions. E.g. aerobic oxidation of alcohols and cross coupling reactions of alcohols leading to esters, amide, imine have been widely and successfully explored [1]. On the other side the reduction of nitroarenes to anilines using NaBH4, H2, silanes, formic acid, CO/H2O is a benchmark reaction for testing their catalytic performances in reduction reactions [2]. During reaserch efforts many supports have been exploited (carbon based supports, polymers, inorganic oxides) but their role is still under discussion. A semicrystalline porous polymeric support, consisting of syndiotactic polystyrene-co-cis-1,4-polybutadiene [3] has been successfully tested in our group and the AuNPS embedded in this polymer matrix (AuNPs-sPSB) were investigated in the reduction of nitrobenzene to aniline. The polymorphic behaviour of the host polymer matrix has been studied to optimize the catalyst performances. The nanoporous crystalline forms of the sPSB matrix, namely  and , allowed a total conversion of nitrobenzene in 40 min at room temperature, with 100% selectivity in aniline. On the contrary the not permeable  crystalline form gave a less reactive and selective catalyst; actually azobenzene and azoxybenzene were detected as intermediates compounds providing information on the cascade of the reduction reactions and the global reaction mechanism. Among the catalysts to date reported in the literature, the AuNPs-sPSB catalyst showed the highest activity (TOF=6000 h-1). The catalyst is very stable under the reaction conditions and reusable for at least three times without loss of catalytic activity. Keywords: Gold Nanoparticles, Polymeric Matrix, Reduction. * Corresponding author: annaritanoschese@gmail.com References [1] A. Corma, H. Garcia, Chem. Soc. Rev. 37 (2008) 2096 [2] S. Fountoulaki, V. Daikopoulou, P. L. Gkizis, I. Tamiolakis, G.S. Armatas, I. N. Lykakis, ACS Catal. 4 (2014) 3504; X. Liu, S. Ye, H.-Q. Li, Y.-M. Liu, Y. Cao, K.-N. Fan, Catal. Sci. Technol. 3 (2013) 3200; L. He, L.-C. Wang, H. Sun, J. Ni, Y. Cao, H.-Y. He, K.-N. Fan, Angew. Chem. Int. Ed. 48 (2009) 9538. [3] A. Buonerba, C. Cuomo, S. Ortega Sánchez, P. Canton, A. Grassi, Chem. Eur. J. 18 (2012) 709; A. Buonerba, A. Noschese, A. Grassi, Chem. Eur. J. 20 (2014) 5478.