Synthesis of an Imprinted Receptor Targeted for Sulfonated Aromatic Pollutants by a Stoichiometric Substructure Imprinting Approach

Creating artificial receptors that can recognize sulfonated anions in water is a difficult task, and employing these receptors to extract sulfonated surfactants and pollutants from water is extremely challenging. We report the synthesis of molecularly imprinted polymers (MIPs) using a stoichiometric sub-structure imprinting approach. The binding pocket of the receptor was generated by the polymerization of a complex of phenylsulfonic acid (PSA) and tweezer-type functional monomers featuring parallel two imidazolium sites. The complexation and stoichiometry of the bisimidazolium monomer with PSA was evaluated by UV and 1H NMR titrations in the pre-polymerization solvents supported by modeling. Further, we studied the solubility and affinity of the imidazolium monomers with PSA easily tuned by counter anions. We report that the large number of co-monomers containing hydroxyl groups around the binding pocket improve the water compatibility and capacity of the imprinted receptors. Finally, we have demonstrated the potential applications of PSA imprinted material by rebinding larger molecules with PSA substructure such as benzyl orange, methyl orange, and linear alkylbenzene sulfonates (LAS). The PSA MIP showed binding capacity around 60 μmol g–1 and affinity with an imprinted factor of two in the solvents containing ≥ 50% water for benzyl orange dye. The developed MIP-based receptors bind sulfonated dyes within 10 min in aqueous environments. Further we demonstrated an MIP-based receptor able to capture LAS from commercial grade sodium dodecyl sulfate and confirmed this by MS measurements.