Renewable 4-HIF/NaOH aerogel for efficient methylene blue removal via cation–π interaction induced electrostatic interaction

A novel porous organic material 4-hydroxyindole-formaldehyde/NaOH (4-HIF/NaOH) aerogel was prepared via a facile polymerization, soaking in NaOH aqueous solution and ambient drying method. 4-HIF/NaOH aerogel porous polymer networks with high surface area have been applied as efficient adsorbents to remove methylene blue from wastewater via synergistic effects of cation–π interaction induced electrostatic interaction, electrostatic interaction and π–π interaction. The adsorption capacity calculated by adsorption isotherms at 303 K was 1016.9 mg g−1 which is higher than those observed for methylene blue on other aerogels and most other materials. Furthermore, the methylene blue loaded 4-HIF aerogel can easily be regenerated with 0.1 M HCl solution and ethanol wash, retaining over 75% of the adsorption capacity after recycling five times.