Synthesis of novel calix[6]-1,4-crown-based netty polymer and its excellent adsorption capabilities for aniline derivatives

Abstract

By introducing four ester groups on p-tert-butylcalix[6]-1,4-crown-4 and then ammonolysis with ethanolamine, p-tert-butylcalix[6]-1,4-crown-4 amido derivative with four terminal hydroxyl groups (4) was obtained in good yield. Further by reacting compound 4 with 1,1,1-tris(tosylatemethyl)propane (6) in NaH/THF system, the novel netty calix[6]-1,4-crown-based polymer 7 was prepared in “4+3” condensation mode. The structure of polymer 7 was confirmed by elemental analysis, IR and 1H NMR spectra. The loose pores and cross-linked netty architecture were observed for polymer 7 in its SEM images. The M n of polymer 7 was 39,816 which indicated an average of approximately 23 calixarene units in each polymer molecule. Polymer 7 exhibited outstanding adsorption abilities for series of aniline derivatives (aniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-nitroaniline, m-nitroaniline and p-nitroaniline). The adsorption percentages for these aniline derivatives were above 90 %. The saturation adsorption capacities for aniline and p-nitroaniline were as high as 2.30 and 2.22 mmol/g, respectively. The adsorption abilities of polymer 7 kept stable at pH 6–10 and it could be re-used after desorption of 10 % HCl. The high adsorption abilities of polymer 7 for aniline derivatives were not just because of π–π stack action of the phenyl groups and the hydrogen bond action, but also due to the stable conformation of calix[6]arene skeleton and big cavity, which were favorable for adsorption of aniline derivatives.