Pd nanoparticles/graphene quantum dot supported on chitosan as a new catalyst for the reduction of nitroarenes to arylam
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ORIGINAL PAPER
Pd nanoparticles/graphene quantum dot supported on chitosan as a new catalyst for the reduction of nitroarenes to arylamines Nastaran Kalanpour1 · Saeid Nejati1 · Sajjad Keshipour1 Received: 20 April 2020 / Accepted: 15 October 2020 © Iranian Chemical Society 2020
Abstract A new heterogeneous catalyst was obtained by growing graphene quantum dots on chitosan and subsequent immobilization of Pd nanoparticles. The catalyst after characterization was used in the reduction of nitroarenes to the corresponding amines by NaBH4 as a weak reducing agent of nitro compounds. The catalyst exhibited excellent catalytic activity and selectivity under mild reaction conditions in water as a green solvent during 1 h. Additionally, the catalyst can be reused for five consecutive runs without any significant decrease in its activity and selectivity. Keywords Heterogeneous catalyst · Graphene quantum dot · Chitosan · Nitroarenes · Reduction
Introduction Development of industrial processes soared concerns about the environmental safety. Nitro compounds are considered as one of the environmental pollutants, so their reduction to the safe amines is the project agenda for many researches [1, 2]. Arylamines have many useful applications as antioxidants, corrosion inhibitors, agrochemicals, photographic developers, and pharmaceuticals [3, 4]. Therefore, catalytic production of arylamines from nitroarenes is gained remarkable attention in the field of chemical industries. One of the key approaches is the utilization of nanomaterials such as metal nanoparticles in heterogeneous catalytic systems due to their advantages of easy separation, and capability of recovery and recycles [5]. Among various transition metal nanoparticles, palladium nanoparticles are able to be used for an array of catalytic goals [6] which its heterogeneous forms have been employed widely in the reduction of nitroaromatics [4]. Agglomeration of metal nanoparticles is a challenge for their successful application because of losing the surface area. Solid supports are important tools to prevent aggregation of the nanoparticles [7]. In recent years, a wide variety of supports have been extended for instance cellulose [8], SBA-15 [9], zeolite [10], and titania [11]. Biopolymers such
as chitosan and cellulose are the leading support [12–14] due to their unique features such as physical and chemical versatility, ease of chemical or physical modification, biodegradability, and suitable sorption capacity [15]. Interests about chitosan as a support for the metal nanoparticles such as palladium nanoparticles have been progressively increased in recent years. Furthermore, the amine functional groups on the surface of chitosan play a key role for increasing metals loading on the polymer [16]. Graphene quantum dots (GQDs) have been extensively considered as a new class of promising organic nanomaterials due to their high stability, excellent biocompatibility, interesting surface area, and low-toxicity [17, 18]. While various nanosupports were introduced for Pd [
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