Graphene–NHC–iridium hybrid catalysts built through –OH covalent linkage. (March 2015)

• Record Type: Journal Article
• Authors: Blanco, Matías; Álvarez, Patricia; Blanco, Clara; Jiménez, M. Victoria; Fernández-Tornos, Javier; Pérez-Torrente, Jesús J.; Oro, Luis A.; Menéndez, Rosa
• Is Part Of: Carbon. Volume 83(2015)
• Page Start: 21
• Page End: 31
• Publication Date: 2015-03
• Subjects: Carbon -- Periodicals; Carbone -- Périodiques; Koolstof; Toepassingen; Electronic journals; 546.681
• DOI: 10.1016/j.carbon.2014.11.016
• Languages: English
• ISSNs: 0008-6223

Abstract

Abstract: Graphene oxide (GO) and thermally reduced graphene oxide (TRGO) were covalently modified with imidazolium salts through their hydroxyl surface groups. The selective reaction of the –OH groups with p -nitrophenylchloroformate produced labile intermediate organic carbonate functions which were used for the covalent anchoring of a hydroxy-functionalized imidazolium salt. Nanohybrid materials containing iridium N-heterocyclic carbene (NHC)-type organometallic complexes were prepared by causing the imidazolium-functionalized materials to react with [Ir(μ-OMe)(cod)]2 . The iridium content of the graphene-based hybrid catalysts, as determined by XPS and ICP-MS was the order of ∼5 and 10 wt.%, for the TRGO and GO-based materials, respectively. The graphene-supported iridium hybrid materials were active in the heterogeneous hydrogen-transfer reduction of cyclohexanone to cyclohexanol with 2-propanol/KOH as the hydrogen source. The thermally reduced graphene–NHC–iridium hybrid catalyst showed the best catalytic performance with an initial TOF of 11.500 h −1, slightly better than the related acetoxy-functionalized NHC iridium homogeneous catalyst. A good catalyst recyclability and stability were achieved.