Facile Green Preparation of Rhodium Nanoclusters Supported Nano-Scaled Graphene Platelets for Sonogashira Coupling Reaction and Reduction of p-Nitrophenol

• Main Authors: Gopiraman Mayakrishnan, Saravanamoorthy Somasundaram, Sana Ullah, Ilangovan Andivelu, Kim Ick Soo, Chung Ill Min
• Format: Article
• Language: English
• Published: MDPI AG 2019-10-01
• Series: Catalysts
• Subjects: grapheneplatelets; rh-nanoclusters; green preparation; 4-nitrophenol; c–c coupling reaction; reusability
• Online Access: https://www.mdpi.com/2073-4344/9/11/908

Rhodium nanoclusters were uniformly dispersed on nano-scaled graphene platelets by a simple ‘mix and heat’ method without using any toxic reagents. Distilled water was used to obtain the homogenous dispersion of Rh-nanoclusters on graphene platelets. The morphology of the resultant catalyst (Rh(0)NCs/GNPs) was studied by means of transmission electron microscope (TEM) and atomic force microscope (AFM) analyses. The X-ray photoemission spectroscope (XPS) result confirmed the metallic form of Rh-nanoclusters in Rh(0)NCs/GNPs. The crystalline property and the interaction between Rh-nanoclusters and graphene platelets (GNPs) were studied by means of XRD and Raman analysis. The Rh-loading in Rh(0)NCs/GNPs was confirmed by scanning electron microscope and energy dispersive spectroscope (SEM-EDS) and inductively coupled plasma-mass spectroscope (ICP-MS) analysis. After being optimized, the Rh(0)NCs/GNPs used as catalyst for the reduction of 4-nitrophenol with NaBH₄ and the Sonogashira coupling reaction between iodobenzene with phenylacetylene. To our delight, the Rh(0)NCs/GNPs showed excellent catalytic activity towards the reduction of 4-nitrophenol with an excellent turnover frequency (TOF) value of 112.5 min^−1. The k_app and k’ values were calculated to be 62.07 × 10^−3 min^−1(0.002 mg of Rh(0)NCs/GNPs) and 31035 × 10^−3 mg^−1 min^−1,respectively. Alike, under the optimal conditions, the Rh(0)NCs/GNPs gave the desired product, diphenylacetylene, in a good yield of 87% with 91% selectivity. The Rh(0)NCs/GNPs can be reused without significant loss in its catalytic activity.