Toluene-induced framework expansion in carbazole-based porous organic polymers anchored with Cu-ZnIn2S4 for ultrafast azeotropic wastewater recovery

Abstract

Toluene, n-propanol, and water are frequently encountered in petrochemical production processes and have a tendency to form azeotropes, thereby complicating their separation. Consequently, achieving efficient separation of these components is essential for both environmental protection and resource conservation. In this study, a composite material comprising a carbazole-based flexible porous organic polymer (POP) and Cu-ZnIn₂S₄ was constructed. The prepared composite achieved 100 % selective separation of toluene from the ternary azeotrope of n-propanol/toluene/water due to π–π conjugation and weak hydrogen bonding interactions between the POP and toluene molecules. Furthermore, the adsorption capacity of the POP/Cu-ZnIn₂S₄ composite for toluene reached an unprecedented 3184 mg/g, surpassing the highest reported capacity to date. Additionally, the selective adsorption of toluene by the POP was coupled with in situ photocatalytic degradation of toluene by Cu-ZnIn₂S₄. During the photocatalytic process, photogenerated charge carriers were effectively separated and transferred via the S-scheme charge transfer pathway, leading to complete degradation of toluene within 3 min. Finally, cycling experiments demonstrated that the POP could be continuously recycled without significant loss of performance.