Cationic porous aromatic framework with hierarchical structure for selective, rapid and efficient removal of anionic dyes from water

Adsorption is a promising technique for water treatment. Porous aromatic frameworks (PAFs) have been witnessed as advanced adsorbents for various applications and PAFs with task-specific functionality and porosity are desirable adsorbents. Herein, a charged PAF, PAF-CH2N(CH3)3I, was prepared through precursor-designed method. The charged PAF is densely and homogeneously functionalized with cationic groups and featured with hierarchical pore structure. The content of the charged groups in the framework reaches up to 52.27 wt% and the hierarchical structure facilitates fast adsorption/desorption of dye molecular. It demonstrates strong affinity, fast adsorption rate, high adsorption efficiency and high adsorption capacity towards not only small model anionic dye but also large-sized one, which can not be adsorbed efficiently by other microporous adsorbents. In addition, benefiting from the hierarchical structure, the charged PAF can be easily regenerated and reused with almost no loss of its efficiency even after 10 adsorption–desorption cycles. These excellent features demonstrate that the charged PAF is a promising adsorbent for wastewater treatment and this study provides a new perspective to explore functionalized PAFs as a versatile type of advanced adsorbents.