Synthesis of macrocyclic polyphenol resin by methylene crosslinked calix[4]arene (MC-[4]H) for the adsorption of palladium and platinum ions

Abstract

A novel macrocyclic polyphenol resin, a calix[4]arene derivative, namely, a methylene crosslinked calix[4]arene (MC-[4]H), was successfully synthesised by demethylation of MC-[4]CH₃. MC-[4]CH₃ was prepared by crosslinking [4]CH₃ with s-trioxane under acidic conditions. Methylation of calix[4]arene ([4]H) is strongly required to protect the oxygen atoms on the phenolic groups. It was found that the adsorption of palladium and platinum optimally occurred at low pH. The maximum loading capacity of palladium on the resin was found to be 0.41 mol kg⁻¹ while that of platinum was 0.23 mol kg⁻¹. The stoichiometries of metal ions were found to be 5 : 1 of the calix[4]arene unit in MC-[4]H to Pd(II) and 3 : 1 of that in MC-[4]H to Pt(IV), respectively.