ORIGINAL PAPER Encapsulation of Nickel Nanoparticles and Homopoly(Vinylsulfonic Acid) in Mesoporous Carbon CMK-3 as an Acid–Metal Bifunctional Catalyst for Tandem Reductive Amination Roozbeh Javad Kalbasi 1 • Parisa Parishani 2 • Omid Mazaheri 2 Received: 2 January 2018 Ó Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Facile and clean transformation for synthesizing secondary arylamines through one-pot reductive amination of aniline has been catalyzed by supported nickel nanocluster and poly(vinylsulfonic acid) into mesoporous carbon CMK-3 (Ni/PVSA/ CMK-3) as a bi-functional metal/acid heterogeneous catalyst. Vinylsulfonic acid has been polymerized in CMK-3 pores by an in situ method. The process was run in the presence of NaBH 4 at room temperature, in a short reaction time, and without secondary product. Various characterization techniques, including FT-IR, XRD, TG, BET, SEM, TEM, DRS-UV, and AAS were employed to disclose the physical and chemical properties of the catalyst. Reaction results demonstrate that the optimized Ni/PVSA/CMK-3 catalyst shows comparable catalytic performance thanks to the nickel metals and the acidic nature of polymer incorporated in mesoporous channels of CMK-3. Besides being eco-friendly (using water as solvent), the method has several advantages such as simple work-up procedure and moderate to high-yield. This catalyst was easily filtered and reused without noticeable loss of activity after 10 runs. Keywords One-pot reductive amination Á Nickel nanoparticles Á Poly(vinylsulfonic acid) Á Acid–metal bifunctional catalyst Introduction Nowadays, amines are of great value with vast consump- tion in industries as intermediates for pharmaceuticals, biologically active compounds, rubbers, solvents, fine chemicals, dyes, herbicides, and in the manufacturing of detergents and plastics [1–3]. Reductive amination has been proved to be the versatile and appropriate procedure of amine synthesis [4, 5]. The reaction is comprised two steps including the formation of an imine during the reaction between primary amine and a carbonyl substrate, and the reduction of the imine with adequate hydride source [5]. There are two detached approaches for reduc- tive amination: the direct approach, which uses the in situ- generated imine, and the indirect approach, which prior isolated imine is consumed [6]. The former method has several advantages such as one-pot procedure, high-yield simple setups, easy separation from the product, being stable and compatible reagents, and mild reaction condi- tions [7]. Many reports on reductive amination reaction with several different catalysts over the past decades have been presented. Among them, heterogeneous catalysis is more convenient than homogenous catalysis because of separa- tion and recovery capabilities [8]. Moreover, it has been proven that two characters of metallic and acidic are nec- essary to perform this reaction; consequently, acid–metal bi-functional heterogeneous catalysts are frequently used in this reaction [9]. Recently, several metal nanoparticles such as Ag, Ni, Cu, and Pd acted as a hydride transfer [10, 11]. Consuming Ni and Cu in catalytic purpose are economically more feasible since nickel and copper are cheaper than precious metals like Ag, Au, Pd, and Pt. Ni 0 activity is much weaker than other metals like Pd 0 and Au 0 . Thus, finding a pro- cedure to intense metal activity is essential. Nickel nanoparticles or cationic nickel complexes have been used & Roozbeh Javad Kalbasi rkalbasi@gmail.com; rkalbasi@khu.ac.ir 1 Faculty of Chemistry, Kharazmi University, Tehran, Iran 2 Department of Chemistry, Shahreza Branch, Islamic Azad University, 311-86145, Isfahan, Iran 123 Journal of Cluster Science https://doi.org/10.1007/s10876-018-1366-6