Preparation of Indole-Based Porous Magnetic Composite via Cation-π Interaction-Driven and Induced Strategy and its Efficient Adsorption of TNT

Abstract

A strategy driven and induced by cation-π interaction was employed to obtain a magnetic porous composite material (Fe₃O₄/PIN) with a uniform dispersion of ferroferric oxide (Fe₃O₄). Utilizing ferric chloride as the catalyst, indole-based porous polymer (PIN) was successfully synthesized through the Friedel-Crafts alkylation reaction. Concurrently with the preparation of the PIN, the cation-π interaction played a pivotal role, not only driving but also inducing the effective dispersion of iron ions from the catalyst around the indole groups. Subsequently, the introduction of ferrous sulfate into the reaction mixture triggered an in-situ reaction, resulting in the uniform distribution of Fe₃O₄ around the indole groups within the PIN. At a temperature of 298 K, Fe₃O₄/PIN demonstrated remarkable adsorption efficiency for TNT, boasting a maximum adsorption capacity of 290.697 mg/g, with the ability to achieve 74% of this capacity within one hour. Moreover, Fe₃O₄/PIN also exhibited a commendable adsorption efficiency for TNT in real water samples. In addition, Fe₃O₄/PIN could be recovered rapidly due to its excellent magnetic properties. After five adsorption-desorption cycles, the adsorption capacity of Fe₃O₄/PIN for TNT remained at 90% of its maximum capacity. Hence, Fe₃O₄/PIN was anticipated to serve as an effective adsorbent for TNT. The uniform distribution of Fe₃O₄ in porous materials through the driving and inducing effects of cation-π is an unprecedented innovation, offering a new perspective and approach to the synthesis and utilization of similar composite materials.