Surface modification of multi-walled carbon nanotubes to produce a new bimetallic Fe/Mn catalyst for the aerobic oxidation of hydrocarbons Fatemeh Nejabat, Saeed Rayati* Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran 15418, Iran A R T I C L E I N F O Article history: Received 23 May 2018 Received in revised form 13 August 2018 Accepted 26 September 2018 Available online 4 October 2018 Keywords: Multi-walled carbon nanotubes Surface modification Bimetallic nanohybrid Metalloporphyrin Aerobic oxidation Molecular oxygen A B S T R A C T Fe/Mn bimetallic heterogenized catalyst [Fe/Mn(THPP)@MWCNT] was prepared by the simultaneous attachment of Mn and Fe porphyrins onto the surface of functionalized multi-walled carbon nanotubes. This new bimetallic nanohybrid displays a superior catalytic performance (81%) in comparison with their analogous monometallic counterparts (36% and 44% for Fe- and Mn-porphyrin respectively) in the oxidation of hydrocarbons with molecular oxygen as the sole oxidant. Experiments comparing bimetallic catalyst with equivalent physical mixtures of monometallic catalysts revealed the catalytic synergistic effect amongst metallic active centers onto the surface of the same nanotube, introducing a new class of bimetallic porphyrin-based catalysts for oxidation reactions. © 2018 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. Introduction The synergistic effects of bimetallic systems play a critical role in the catalytic performance and energy storage of these hybrid materials, which have been of great interest to researchers since long years ago [1–5]. The scope of such studies usually has been limited to the supported precious metal nanoparticles or multimetallic clusters, omitting supported transition metal com- plexes [6–8]. Recently, various materials with different physical and chemical properties were applied as a solid support for preparing heterogenized catalysts to improve the efficiency of hybrid nanomaterials [9–14]. Among these various materials, carbon-based materials as promising candidates for preparing hybrid nanomaterials display significant activity for catalytic systems [14–18]. A number of procedures are available to modify or functionalize the surface of nanostructured materials to improve their properties [19–22]. Metalloporphyrins as the powerful and effective catalyst in oxidation reactions could be an appropriate candidate for immobilization on the solid supports to produce heterogenized catalysts [23–27]. According to the literature, the catalytic efficiency of immobilized porphyrins strongly depends on the active metal center of metalloporphyrins, which controls the activity, stability and selectivity of porphyrin-based catalysts [28– 30]. We have recently prepared a number of immobilized metalloporphyrins as efficient catalysts in oxidation reactions [31–33]. In some cases thereof, we also compared the effect of active metal center on the catalytic activity of the heterogenized catalysts [34,35]. By having different metal complexes attached onto the surface of the same support, the individual advantages of each active metal center would be added to the catalyst and a new class of bimetallic catalysts would be produced. Few reports available on porphyrin-based bimetallic systems merely cover twin-porphyrin or phosphine-porphyrin derivatives, but not immobilized porphyrins [36,37]. Here, we report the easy preparation of a new family of bimetallic nanohybrid based on the immobilization of metal- loporphyrins onto the surface of solid supports for the design of the advanced catalyst. Experimental section Physical measurements FTIR spectra were recorded using an ABB Bomem: FTLA 200-100 spectrophotometer with potassium bromide pellets in the range 400–4000 cm 1 . A Varian AA240 atomic absorption spectrometer was employed to determine the amount of metalloporphyrin complexes onto the solid support. The UV–Vis spectra were recorded by a Cam-Spec-M330 model in 2 mm path length quartz * Corresponding author. E-mail address: rayati@kntu.ac.ir (S. Rayati). https://doi.org/10.1016/j.jiec.2018.09.044 1226-086X/© 2018 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. Journal of Industrial and Engineering Chemistry 69 (2019) 324–330 Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal home page : www.elsevier.com/loca te/jiec