The Role of a Nitro Substituent in C ‐Phenylcalix[4]resorcinarenes to Enhance the Adsorption of Gold(III) Ions

Abstract Nitro‐substituted C ‐phenylcalix[4]resorcinarene derivatives were synthesized and evaluated for gold(III) ions adsorption. All the nitro‐substituted C ‐phenylcalix[4]resorcinarenes showed higher maximum adsorption capacity as compared to the bare C ‐phenylcalix[4]resorcinarene. A remarkable high adsorption capacity of up to 272.70 mg g −1 was obtained after 2 h on the C ‐2‐nitrophenylcalix[4]resorcinarene (Calix‐2NO 2 ), which was two times higher than that of the C ‐phenylcalix[4]resorcinarene. The adsorption capacity was affected by the position of the nitro group. The highest adsorption capacity observed on the Calix‐2NO 2 was closely related to the strongest supramolecular interactions between the gold(III) ions and the Calix‐2NO 2 , as supported by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance ( 1 H‐NMR) spectroscopies as well as the desorption study. This study demonstrated that the macrocyclic material, namely nitro‐substituted C ‐phenylcalix[4]resorcinarenes, were effective adsorbents having good reusability, and thus, applicable for gold(III) ions recovery.