A cost-effective β-cyclodextrin polymer for selective adsorption and separation of acetophenone and 1-phenylethanol via specific noncovalent molecular interactions

Abstract

To separate acetophenone (AP) and 1-phenylethanol (PE), a kind of cost-effective β-cyclodextrin based polymeric sorbent (CE-CDP) was constructed by crosslinking β-cyclodextrin with toluene-2,4-diisocyanate trimer. According to the characteristic results, the structure of the CE-CDP consisting of β-cyclodextrin cavity, aromatic urethane bond and unique isocyanurate ring was proved substantially. It was shown that crosslinking process would enhance the thermal stability, and the incorporation of the unique crosslinking units into CE-CDP's network potentially improved the selective adsorption performance compared to analogous polymer with non-isocyanurate ring structure. The static adsorption performance of CE-CDP in single solute system was investigated. The adsorption capacity of AP was much higher than that of PE, indicating that CE-CDP exhibits much stronger affinity toward AP over PE. Based on the results, we found that the spontaneous adsorption processes of AP and PE onto CE-CDP could be well described by pseudo-second order kinetics, Langmuir and Freundlich isotherm models. And the preferential AP adsorption over PE (selectivity≈6) was further verified through binary competitive adsorption. In addition, the density functional theory calculations showed that the coexistence of β-cyclodextrin cavity, aromatic urethane bond and isocyanurate ring endows CE-CDP with high AP adsorption capacity and selectivity. The theoretical results also indicated that the noncovalent interactions involving the intermolecular hydrogen bonding, π-π interactions and electrostatic interaction are favorable for binding AP rather than PE. In conclusion, CE-CDP was proved to be a good adsorbent for selective separation of AP and PE with mass producibility, low cost, high reusability and wide application prospect.