A citric acid functionalized graphene oxide nanocomposite was successfully synthesized and the structure and morphology of the nanocatalyst were comprehensively characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, X-ray diffraction patterns, atomic force microscopy images, scanning electron microscopy images, transmission electron microscopy images, and thermogravimetric analysis. The application of this nanocatalyst was exemplified in an important condensation reaction to give imidazole derivatives in high yields and short reaction times at room temperature. The catalyst shows high catalytic activity and could be reused after simple work up and easy purification for at least six cycles without significant loss of activity, which indicates efficient immobilizing of citrate groups on the surface of graphene oxide sheets.

Abstract
 1. Introduction
 2. Experimental
  2.1. General
  2.2. Synthesis of catalyst
  2.3. General procedure for the synthesis ofimidazole derivatives 3a-n
 3. Results and Discussion
  3.1. Characterization of GO/CA catalyst
  3.2 Optimization of different parameters inthe synthesis of imidazole derivatives
  3.3 Comparison the efficiency of synthesizednanocatalyst
  3.4. Mechanistic evaluation
  3.5. Catalyst recyclability examination
 4. Conclusions
 References

• Ali Maleki(Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran University of Science and Technology) Corresponding Author
• Zoleikha Hajizadeh(Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran University of Science and Technology)
• Hamid Abbasi(Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran University of Science and Technology)